FXUS66 KMTR 221117 AFDMTR AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA 417 AM PDT FRI MAR 22 2013 .DISCUSSION...AS OF 3:45 AM PDT FRIDAY...CLEAR SKIES ACROSS MOST OF THE DISTRICT THIS EARLY MORNING PER SATL IMAGERY AND SFC OBS. THE EXCEPTION IS HALF MOON BAY WHICH IS REPORTING 3 MILES IN FOG WITH A 300 FT CEILING. GOES-W FOG DEPTH PRODUCT AT 3 AM IS INDC THAT THE TOP OF THE STRATUS DECK AT HALF MOON BAY IS AROUND 700 FT...SO WOULD EXPECT IT TO BURN OFF SHORTLY AFTER SUNRISE. THE GRADIENT PICTURE AT 3 AM IS INDC A PRETTY ROBUST NORTHERLY GRADIENT BETWEEN ARCATA-SFO...8.5 MB AND A 13.7 MB GRADIENT BETWEEN SFO-LAS VEGAS. HOWEVER...IT APPEARS THAT THE BOUNDARY LAYER HAS DECOUPLED WITH LIGHT WINDS AT THE SFC...LET ALONG THE FOG AT HALF MOON BAY. EVEN IN THE NORTH BAY MTNS THE HIGHEST GUST SO FAR IS 28 MPH AT THE ATLAS PEAK RAWS. IN THE EAST BAY HILLS POVERTY FLATS RAWS IS REPORTING GUSTS OVER 50 MPH. HOWEVER...THAT IS AN ISOLATED READING WHICH IS SIGNIFICANTLY HIGHER THAN OTHER SPOTS IN THE EAST BAY HILLS AND COULD BE THE RESULT OF CHANNELING DUE TO TOPOGRAPHY OR EVEN A BAD OB. HAVE DECIDED TO CANCEL THE WIND ADVISORY THAT WAS IN EFFECT FOR THE NORTH BAY MOUNTAINS THIS MORNING INTO THE EARLY AFTN. WINDS HAVE NOT MIXED DOWN THIS MORNING...AND ARE SIGNIFICANTLY LIGHTER THAN THE 00Z/06Z NAM AND THE 00Z WRF 925 MB WIND FCST. THERE COULD STILL BE STRONG GUSTS IN THE HILLS SHORTLY AFTER SUNRISE AS THE LOWER LEVELS MIX...BUT THE DURATION OF STRONG WINDS WILL BE BRIEF. AS HAS BEEN THE OVERRIDING THEME SINCE JANUARY 1ST...RIDGING ALONG THE COAST WILL KEEP THE DISTRICT DRY AND MILD INTO EARLY NEXT WEEK. WITH THE LOW DEW PTS THERE COULD BE SOME "LONG THERMOMETERS" WITH AFTN HIGHS IN THE 60S TO LOWER 70S AND OVERNIGHT LOWS DOWN INTO THE UPPER 30S AND 40S. THE RIDGE WILL FLATTEN LATE TUESDAY AS A SERIES OF DISORGANIZED SYSTEMS MOVE INTO THE PACIFIC NORTHWEST. WEAK TROUGHING ALONG THE COAST WILL BRING A CHANCE OF LIGHT RAIN TO THE DISTRICT...MAINLY NORTH OF THE MONTEREY BAY AREA...TUESDAY NIGHT INTO THURSDAY. HOWEVER...AS OF NOW IT LOOKS LIKE RAINFALL TOTALS WILL BE LIGHT. WITH SEASONAL RAINFALL RUNNING 68-80 PERCENT OF NORMAL (THANKS TO ABOVE NORMAL RAINFALL IN NOVEMBER AND DECEMBER 2012) IT IS GETTING LATE IN THE SEASON TO MAKE UP THE DEFICIT. && .AVIATION...AS OF 10:47 PM PDT THURSDAY...VFR IS FORECAST FOR THE PERIOD. NON-CONVECTIVE LOW LEVEL WIND SHEAR (LLWS) IS POSSIBLE AT KOAK VERY LATE TONIGHT AND FRIDAY MORNING. SUNNY WEATHER...DIURNAL WARMING/MIXING WILL HELP RECONNECT SURFACE AND LOW LEVEL WINDS ALL AREAS BY LATE FRIDAY MORNING. VICINITY OF KSFO...VFR. KSFO BRIDGE APPROACH...VFR. MONTEREY BAY AREA TERMINALS...VFR. && .MTR WATCHES/WARNINGS/ADVISORIES... .TDAY...SCA...PT REYES TO PIGEON PT 0-10 NM SCA...PIGEON PT TO PT PINOS 0-10 NM SCA...PT ARENA TO PT REYES 0-10 NM FROM 9 AM SCA...PT ARENA TO PIGEON PT 10-60 NM FROM 9 AM GLW...PT ARENA TO PT REYES 0-10 NM UNTIL 9 AM GLW...PT ARENA TO PIGEON PT 10-60 NM UNTIL 9 AM SCA...PT PINOS TO PT PIEDRAS BLANCAS 0-10 NM SCA...PIGEON PT TO PT PIEDRAS BLANCAS 10-60 NM SCA...ROUGH BAR ADVISORY FOR SF BAR && $$ PUBLIC FORECAST: STROBIN AVIATION/MARINE: RILEY VISIT US AT WWW.WEATHER.GOV/SANFRANCISCO FOLLOW US ON FACEBOOK, TWITTER, AND YOUTUBE AT: WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.SANFRANCISCOBAYAREA.GOV WWW.TWITTER.COM/NWSBAYAREA WWW.YOUTUBE.COM/NWSBAYAREA  FXUS66 KMTR 301147 AFDMTR AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA 447 AM PDT SAT MAR 30 2013 .DISCUSSION...AS OF 3:14 AM PDT SATURDAY...SATELLITE IMAGERY SHOWS A MIXTURE OF LOW AND HIGH CLOUDS OVER THE AREA AT THIS TIME...AND SURFACE OBSERVATIONS INDICATE SOME LOW CEILINGS NEAR THE COAST...GENERALLY BELOW 1000 FEET. NO VISIBILITY RESTRICTIONS DUE TO FOG AT THIS TIME. RADAR IS STILL SHOWING SOME WEAK ECHOES OFF THE COAST AS WELL AS OVER THE NORTH BAY. SO FAR THE ONLY RAINFALL BEING PICKED UP HAS BEEN IN PESCADERO CREEK IN SAN MATEO COUNTY WHERE 0.02 HAS REGISTERED SOMETIME IN THE LAST 3 HOURS. MEANWHILE...THE CUT-OFF LOW IS STILL OFF THE COAST AND IS CURRENTLY LOCATED NEAR 35N/133W. THIS LOW WILL GRADUALLY WORK ITS WAY EASTWARD TODAY WITH SHOWER BANDS SPREADING OVER THE DISTRICT BEGINNING LATER TODAY. WITH MORE WIDESPREAD SHOWERS ARE EXPECTED ON SUNDAY AS THE UPPER LOW NEARS THE COAST...AND THEN MOVES OVER SAN FRANCISCO BY LATE IN THE DAY. THUNDERSTORMS ARE ALSO POSSIBLE WITH THE PROXIMITY TO THE LOW CENTER...MAINLY DURING THE DAY SUNDAY. RAINFALL AMOUNTS WITH THIS SYSTEM RANGE FROM ABOUT A QUARTER OF AN INCH TO AROUND AN INCH WITH THE HIGHER AMOUNTS EXPECTED IN THE COASTAL MOUNTAINS. SHOWERS TO TAPER OFF BY MONDAY MORNING WHEN HIGH PRESSURE REBUILDS OVER THE WEST. THE NEXT RAIN CHANCES WILL OCCUR WEDNESDAY NIGHT AND THURSDAY AS AN UPPER TROUGH MOVES ONTO THE COAST...WITH ANOTHER SYSTEM POSSIBLE BY NEXT WEEKEND. && .AVIATION...AS OF 4:47 AM PDT SATURDAY...CURRENTLY THE IR SATELLITE IMAGE IS SHOWING MID TO HIGH CLOUDS AND SOUTHERLY FLOW OVER THE FORECAST AREA. THE GOES IFR PROB PROD IS INDICATING IFR PROB GREATER THAN 60% OVER PORTIONS OF SAN FRANCISCO BAY WITH KOAK OB INDICATING BKN005. SOUTHERLY FLOW SHOULD HELP TO KEEP THE LOW CIGS OUT OF KSFO BUT THERE MAY BE SOME IFR CIGS OVER THE APPROACH. RUNWAYS SHOULD REMAIN DRY THIS MORNING WITH SHOWERS EXPECTED TO DEVELOP LATER THIS EVENING. VICINITY OF KSFO...VFR IS ANTICIPATED TODAY WITH A LOW PROBABILITY OF IFR CIGS THIS MORNING. IF IFR DOES DEVELOP CONDITIONS SHOULD IMPROVE NO LATER THAN 1700Z. GENERALLY LIGHT WINDS WILL INCREASE OUT OF THE SOUTHWEST TO 10 TO 12 KT BY 2100Z. KSFO BRIDGE APPROACH...SIMILAR TO KSFO WITH A HIGHER PROB OF IFR CIGS THIS MORNING. IF IFR CIGS DO DEVELOP CONDITIONS SHOULD IMPROVE BY 1700Z. MONTEREY BAY AREA TERMINALS...LIFR CIGS THIS MORNING WILL IMPROVE TO IFR BY 1700Z WITH CONTINUED IMPROVEMENT TO VFR BY 2000Z. && .MTR WATCHES/WARNINGS/ADVISORIES... .TDAY...NONE. $$ PUBLIC FORECAST: SIMS AVIATION/MARINE: LARRY VISIT US AT WWW.WEATHER.GOV/SANFRANCISCO FOLLOW US ON FACEBOOK, TWITTER, AND YOUTUBE AT: WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.SANFRANCISCOBAYAREA.GOV WWW.TWITTER.COM/NWSBAYAREA WWW.YOUTUBE.COM/NWSBAYAREA  FXUS66 KMTR 051117 AFDMTR AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA 417 AM PDT FRI APR 5 2013 .DISCUSSION...AS OF 3:25 AM PDT FRIDAY...A FEW PESKY SHOWERS AND SPRINKLES ARE STILL CONTINUING ACROSS THE NORTH BAY EARLY THIS MORNING. HOWEVER IN GENERAL EXPECT THIS TO END BY SUNRISE. SKIES ARE MOSTLY CLOUDY ACROSS THE DISTRICT WITH A 2000-3000 FOOT CLOUD DECK BEING REPORTED MOST AREAS. THIS WILL SLOWLY MIX OUT BY AFTERNOON WITH PARTLY CLOUDY SKIES AND SEASONABLY COOL TEMPERATURES IN THE 60S FORECAST FOR MOST LOCATIONS. PATTERN DETAILS REMAIN SOMEWHAT MUDDLED FOR THE WEEKEND FORECAST AND ITS BEEN THAT WAY FOR DAYS NOW. YESTERDAYS FRONT CAME THROUGH AS ADVERTISED WITH SOLID MODEL AGREEMENT IN BRINGING THAT SYSTEM IN FROM THE WEST. THE SHORTWAVES THAT WILL IMPACT THE PACIFIC NW AND NORTHERN CALIFORNIA THIS WEEKEND ARE EMBEDDED IN A SWIFT JET STREAM THAT IS SITUATED TO OUR NORTH...APPROXIMATELY ALONG THE 40N LATITUDE. MODEL TIMING OF THESE SYSTEMS IS DISJOINTED AMONGST ALL OF THE MODELS AS THESE FEATURES EJECT TOWARDS THE WEST COAST. BEST ESTIMATE BRINGS THE NEXT WEAK BOUNDARY INTO NORTHERN CALIFORNIA SATURDAY MORNING WITH THE REMNANTS OF A WEAK FRONT MAINLY IMPACTING THE NORTH BAY ON SATURDAY. FORECAST WILL CONTINUE TO SHOW SLIGHT CHANCE OF SHOWERS WITH ONLY A FEW HUNDREDTHS EXPECTED. THE 06Z NAM SOLUTION BRINGS MEASURABLE RAIN ALL THE WAY TO SAN FRANCISCO BY AROUND 18Z SATURDAY. AREAS FROM SAN JOSE SOUTHWARD WILL HAVE LITTLE CHANCE FOR SEEING ANY SHOWERS THIS WEEKEND BUT LOCATIONS TO THE NORTH COULD SEE SOME HIT AND MISS SHOWERS AT TIMES BUT AGAIN WITH VERY LIGHT QPF. THE NEXT WEAK SYSTEM IS PROGGED BY THE NAM TO REACH THE NORTH BAY SUNDAY MORNING WITH ANOTHER ROUND OF LIGHT SHOWERS...GENERALLY A TENTH OR LESS. THUS WILL KEEP SLIGHT CHANCE OF SHOWERS GOING IN THE FORECAST ON SUNDAY...AGAIN WITH THE BEST CHANCES BEING FOCUSED IN THE NORTH BAY. THE FINAL UPPER SHORTWAVE AND SUPPORT WILL EJECT TOWARDS THE SIERRA BY SUNDAY EVENING...EFFECTIVELY ENDING SHOWER CHANCES ACROSS THE GREATER BAY AREA. HIGH PRESSURE WILL BUILD MONDAY AFTERNOON THROUGH WEDNESDAY WITH MILD TO WARM WEATHER AND MOSTLY CLEAR SKIES. ALTHOUGH THE LATEST SOLUTIONS AREN'T NEARLY AS WARM AS 1 TO 2 DAYS AGO. AN UPPER TROUGH WILL APPROACH THE WEST COAST BY THURSDAY OR FRIDAY WITH A RETURN TO ONSHORE FLOW AND AT LEAST A CHANCE OF MORE NORTH BAY SHOWERS BY NEXT WEEKEND. && .AVIATION...AS OF 4:15 AM PDT THURSDAY...CIGS BLANKET THE ENTIRE BAY REGION THIS MORNING IN THE MVFR TO VFR RANGE...BASED UPON SFC OBS AND GOES-R FLS PRODUCTS. WILL FOLLOW SHORT TERM MODEL GUIDANCE AND ALLOW FOR CLEARING THIS AFTERNOON. ONSHORE FLOW WILL PREVAIL WITH WESTERLY WINDS UP TO 15 KT. CIGS AND MARINE LAYER WILL RETURN TONIGHT...BUT SOME UNCERTAINTY EXISTS GIVEN ANOTHER WEAK FRONTAL BOUNDARY MOVING INTO THE N BAY SATURDAY MORNING. CONF MEDIUM. VICINITY OF KSFO...CIGS WILL HOVER AROUND 3K FEET AND WILL USE MVFR CIGS THROUGH 18Z. A FEW PASSING LOWER CLOUDS IN THE 500-1500 FOOT LEVEL MAINLY BRIEFLY IMPACT KOAK AND KSFO...HIGHER BASES WILL PREVAIL FOR A MAJORITY OF THE MORNING. KSFO BRIDGE APPROACH...SIMILAR TO KSFO. MONTEREY BAY AREA TERMINALS...MVFR CIGS THROUGH 18-19Z WITH GRADUAL CLEARING THIS AFTERNOON. CIGS RETURN EARLY TONIGHT WITH CONT ONSHORE FLOW. && .MTR WATCHES/WARNINGS/ADVISORIES... .TDAY...NONE. $$ PUBLIC FORECAST: RWW AVIATION/MARINE: MM VISIT US AT WWW.WEATHER.GOV/SANFRANCISCO FOLLOW US ON FACEBOOK, TWITTER, AND YOUTUBE AT: WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.SANFRANCISCOBAYAREA.GOV WWW.TWITTER.COM/NWSBAYAREA WWW.YOUTUBE.COM/NWSBAYAREA  FXUS66 KMTR 251750 AFDMTR AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA 1050 AM PDT THU APR 25 2013 .DISCUSSION...AS OF 8:45 AM PDT THURSDAY...MODERATE ONSHORE FLOW WITH AN ABUNDANT STRATUS FIELD OFFSHORE BROUGHT STRATUS WELL INLAND INTO THE DELTA OVERNIGHT AND THIS MORNING. PATCHY COASTAL DRIZZLE WAS ALSO REPORTED THIS MORNING AND A QUICK UPDATE TO THE FORECAST WAS MADE TO ACCOUNT FOR THIS. OTHERWISE...TEMPERATURES OVERNIGHT FELL INTO THE MID 40S TO MID 50S...NEAR NORMAL FOR THE END OF APRIL. FOR TODAY...A SIMILAR UPPER LEVEL AND SURFACE PATTERN WILL BE PRESENT ACROSS THE REGION COMPARED TO YESTERDAY. TEMPERATURES THIS AFTERNOON WILL RISE INTO THE UPPER 50S TO MID 60S ALONG THE COAST...TO THE MID 60S TO LOW 70S INLAND. LOW CLOUDS THROUGH MUCH OF THE REGION WILL SLOWLY DISSIPATE INTO THE AFTERNOON HOURS. A FEW AREAS ALONG THE COAST MAY EXPERIENCE MOSTLY CLOUDY SKIES THROUGH THE DAY AS THE STRATUS FIELD CONTINUES TO EXPAND OFFSHORE WITH MODERATE ONSHORE FLOW THIS AFTERNOON. CURRENT FORECAST LOOKS RIGHT ON TRACK WITH HIGH PRESSURE BUILDING INTO THE REGION AND A WARMING TREND INTO THE WEEKEND. .PREVIOIUS DISCUSSION...AS OF 2:20 AM PDT THURSDAY...THE MARINE LAYER HAS DEEPENED CONSIDERABLY AND THE FORT ORD PROFILER CURRENTLY SHOWS IT TO BE WELL OVER 3000 FEET DEEP. SATELLITE FOG PRODUCT SHOWS COASTAL STRATUS HAS PUSHED WELL INLAND ACROSS THE NORTH BAY AS WELL AS INTO THE MONTEREY BAY AREA. THERE IS NO LONGER ANY OFFSHORE COMPONENT TO THE SURFACE PRESSURE GRADIENTS AND THE SFO- SAC GRADIENT IS NOW 3.4 MB. EXPECT ANOTHER COOL DAY TODAY WITH HIGHS IN THE 60S AND 70S. HIGH PRESSURE BUILDING INTO CALIFORNIA ON FRIDAY WILL PROVIDE A BIT OF A WARMING TREND THROUGH THE WEEKEND. TEMPERATURES ARE EXPECTED TO LEVEL OFF WITH HIGHS IN THE 60S TO MID 80S INTO EARLY NEXT WEEK. THE PRESENCE OF LOW CLOUDS IS EXPECTED TO LESSEN BEGINNING DURING THE WEEKEND AND INTO NEXT WEEK AS HIGH PRESSURE BUILDS OVER THE STATE. NO CHANGE IN THE DRY PATTERN AS WELL WITH THE LATEST 8-14 DAY PRECIPITATION PROBABILITY OUTLOOK FROM THE CPC KEEPS THE STATE UNDER AN AREA OF MUCH BELOW AVERAGE CHANCES OF RAIN THROUGH THE PERIOD OF MAY 2ND THROUGH MAY 8TH. THE CORRESPONDING TEMPERATURE OUTLOOK PAINTS MUCH OF THE WESTERN STATES UNDER AN ABOVE NORMAL TEMPERATURES WITH COASTAL AREAS AT NEAR NORMAL. && .AVIATION...AS OF 10:50 AM PDT THURSDAY...CLOUDS HAVE BEEN DISSIPATED MUCH SLOWER THAN EXPECTED AROUND SF BAY SO PUSHED FOR LATER TIMES FOR THOSE TERMINALS. OVERALL LOOKS LIKE A BIT OF A PATTERN THAT WE WOULD TYPICALLY SEE MORE IN THE SUMMER -- WIDESPREAD LOW CLOUDS OVERNIGHT GIVING WAY TO CLEARING INLAND FIRST THEN THE COAST THROUGH THE DAY. CURRENT MARINE LAYER IS DEEP AT OVER 3000 FEET. AGREE WITH CWAS THAT AN EARLY RETURN TONIGHT IS A DEFINITE POSSIBILITY. WENT 04Z FOR THE MOMENT ALTHOUGH THAT MAY BE TOO OPTIMISTIC. WINDS SHOULD MOSTLY NOT BE A FACTOR. JUST MODERATE CONFIDENCE. VICINITY OF KSFO...MVFR THROUGH AROUND 19Z CURRENTLY FORECAST. GOES-R FLS MVFR IFR PROBABILITIES DOES SHOW DEFINITELY IMPROVEMENT ALONG THE SOUTHER EDGE OF CLOUDS THROUGH THE BAY SUGGESTING THAT WE ARE NOT LOOKING AT AN ALL DAY EVENT -- AND COULD EVEN COME IN A FEW MINUTES BEFORE 19Z. CLOUDS RETURN TONIGHT AND COULD RETURN EARLIER THAN THE CURRENT 04Z TIME ADVERTISED. WINDS WILL PICK UP THIS AFTERNOON AND GUST OVER 15KT AT TIMES FROM THE W TO NW. MODERATE CONFIDENCE. KSFO BRIDGE APPROACH...SIMILAR TO KSFO. MONTEREY BAY AREA TERMINALS...CLOUDS HAVE CLEARED OUT OVER THE BAY AND ARE STARTING TO CLEAR NEAR THE COAST NOW. SOME BREAKS ALSO DETECTED TOWARD KSNS. FEEL VFR RETURN CLOSE TO 19Z AT KSNS. KMRY SHOULD BREAK OUT ANY MINUTE. CLOUDS RETURN TONIGHT AROUND 02Z. MODERATE CONFIDENCE. && .MTR WATCHES/WARNINGS/ADVISORIES... .TDAY...SCA...SF BAY FROM 2 PM && $$ PUBLIC FORECAST: RILEY/SIMS AVIATION/MARINE: BELL VISIT US AT WWW.WEATHER.GOV/SANFRANCISCO FOLLOW US ON FACEBOOK, TWITTER, AND YOUTUBE AT: WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.SANFRANCISCOBAYAREA.GOV WWW.TWITTER.COM/NWSBAYAREA WWW.YOUTUBE.COM/NWSBAYAREA  FXUS66 KMTR 271753 AFDMTR AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA 1053 AM PDT SAT APR 27 2013 .DISCUSSION...AS OF 8:30 AM SATURDAY...EXTENSIVE CLOUD COVER THIS MORNING WITH LOCALLY DENSE FOG IN MONTEREY BAY AND A FEW REPORTS OF DRIZZLE. THE MARINE INVERSION IS AROUND 1500 FT KEEPING CEILING HEIGHTS LOW. STARTING TO SEE EARLY SIGNS OF THE CLOUD DECK THINNING IN THE SANTA CLARA VALLEY ON VISIBLE SATELLITE IMAGERY. CLOUDS WILL CLEAR BACK TO THE COAST BY MID TO LATE MORNING AND TEMPS AWAY FROM THE COAST WILL MOSTLY RANGE FROM THE UPPER 60S TO LOW 80S BY AFTERNOON. FORECAST ON TRACK AND NO UPDATES AT THIS TIME. && .PREV DISCUSSION...FOG PRODUCT IR SATELLITE IMAGERY SHOWS MARINE STRATUS HAVING NOW EXTENDED WELL INTO THE COASTAL VALLEYS. THIS HAS OCCURRED DESPITE A SIGNIFICANT SHALLOWING OF THE MARINE LAYER OVER THE PAST 24 HRS...WITH BOTH THE BODEGA BAY AND FT ORD PROFILERS INDICATING THE DEPTH HAVING DECREASED FROM AROUND 1800 TO 1100 FT. EXTENSIVENESS OF THE STRATUS REFLECTS A COMMENSURATE MODERATE INCREASE IN THE ONSHORE SEA LEVEL PRESSURE GRADIENT THAT HAS OCCURRED...2.8 MB HIGHER AT SFO THAN AT SAC AT 10Z TODAY...IN CONTRAST TO 1.8 MB AT THE SAME TIME YESTERDAY. PROFILERS ALSO SHOW 2C TO 3C OF WARMING OF THE AIR MASS ABOVE THE MARINE LAYER SINCE THIS TIME YESTERDAY. THIS IS REFLECTED IN TEMP OBS IN THE HIGHER HILLS...WITH THE RAWS SITE AT THE SUMMIT OF MT DIABLO FOR EXAMPLE REPORTING A TEMPERATURE OF 64F AT 3:15 AM...IN CONTRAST TO 56F AT 3:15 AM ON FRIDAY. IN GENERAL...WE ARE LOOKING AT CONTINUED DRY CONDITIONS THROUGH THE LENGTH OF THE FORECAST PERIOD...BUT WITH A SIGNIFICANT WARMING TREND ESPECIALLY INLAND OVER THE WEEKEND AND INTO THE FIRST PART OF NEXT WEEK...AS A STRONG UPPER LEVEL RIDGE OF HIGH PRESSURE BUILDS INTO AND THEN PERSISTS ALONG THE COAST. AS THIS OCCURS SIGNIFICANT ADDITIONAL WARMING ALOFT WILL OCCUR...WITH 850 MB TEMPS ABOVE KOAK PROJECTED TO INCREASE TO 16-17C BY LATE SATURDAY...AND THEN TO NEAR 18C SUNDAY AFTERNOON AND 19C MONDAY AFTERNOON. TO PUT THIS IN SOME PERSPECTIVE...THE ALL TIME RECORD KOAK 850 MB TEMP FOR THE MONTH OF APRIL...FOR THE PERIOD 1948 TO 2012...IS 22.5C SO THIS IS GETTING UP THERE. DID SOME COMPARISON WITH THE BASIC SYNOPTIC ANALYSIS FOR THE RECORD LEVEL...FOR AROUND THE END OF APRIL...MAX TEMP EVENT OF APRIL 26-27 2004...WHEN STS REACHED 94F...LVK 93F...AND SNS 100F...AND NOT ALL THAT DISSIMILAR IN TERMS OF 500 MB HEIGHT PATTERN AND 850 MB TEMPS...ALBEIT BOTH WERE A BIT HIGHER IN THAT CASE AND THE LOWER LEVEL FLOW THEN SOMEWHAT MORE OFFSHORE ORIENTED. CURRENT FORECAST CALLS FOR MAX TEMPS ON MONDAY OF 89F AT STS...90 AT LVK...BUT JUST 73F FOR DOWNTOWN SAN FRANCISCO AND 80F AT SNS AS A SHALLOW MARINE LAYER AND ONSHORE FLOW ARE EXPECTED TO CONTINUE. AND THIS IS WHERE IT GETS TRICKY...WHERE EXACTLY THE SHARP GRADIENT BETWEEN THE COOL MARINE AIR AND VERY WARM AIR MASS INLAND ENDS UP. 00Z NAM MOS GUIDANCE FOR SUNDAY MAX TEMP AT STS FOR EXAMPLE IS 78F...WHILE CORRESPONDING ECMWF MOS HAS IT AT 89F. UPSHOT IS EXPECTATION OF A SIGNIFICANT PROGRESSIVE WARM-UP WELL INLAND OVER THE WEEKEND AND INTO MONDAY...BUT ONLY MUCH MORE MODEST INCREASES CLOSE TO THE COAST. IN THE EXTENDED...GENERAL AGREEMENT BETWEEN THE GFS AND ECMWF THAT A SHORT-WAVE TROUGH WILL BRUSH THROUGH FROM THE NW AROUND MONDAY NIGHT AND RESULT IN SOME COOLING OF THE AIR MASS ALOFT. BEHIND IT HOWEVER...LOW LEVEL FLOW LOOKS TO TURN MORE OFFSHORE AS SURFACE HIGH PRESSURE BUILDS INTO THE PAC NW AND THUS BOTH WARMING NEAR THE COAST...BUT A BIT OF A COOLING TREND INLAND. THEREAFTER...CURRENT INDICATIONS ARE THAT THE UPPER LEVEL RIDGE WILL REBUILD...AND THUS BACK TO INCREASING TEMPS ALOFT AND UNSEASONABLY WARM TEMPS AT LEAST WELL INLAND. CLOSER TO THE COAST IT GETS TOUGHER AS POSSIBILITIES RANGE FROM A MINIMAL MARINE LAYER/ONSHORE FLOW AND THUS POTENTIALLY ALSO VERY WARM TEMPS...TO CONTINUING DGEX MODEL INDICATIONS OF A POSSIBLE SOUTHERLY STRATUS SURGE UP THE COAST IN THE LATE WEDNESDAY TO THURSDAY TIME FRAME. && .AVIATION...AS OF 10:53 PM PDT SATURDAY...FOR 18Z TAFS. LOW CLOUD DECK IS RETREATING QUICKLY NOW WITH CLOUD DEPTH FAIRLY SHALLOW AT AROUND 1000 FEET. OBSERVATION AT SAN MATEO BRIDGE HAS GONE FEW AND EXPECT RAPID CLEARING FOR KOAK AND KSFO BY 1830Z. CIGS HAVE ALREADY PULLED BACK FROM THE MONTEREY PENINSULA. EXPECT MODERATE SEABREEZE THIS AFTERNOON WITH EARLY RETURN OF STRATUS BUT SHOULD HOLD OFF UNTIL AFTER 04Z FOR BAY AREA AIRPORTS. VICINITY OF KSFO...CIGS EXPECTED TO MIX OUT BY 1830Z. MODERATE SEABREEZE FROM 15 KT SUSTAINED WITH GUSTS 25 KT THROUGH 04Z. CIGS TO RETURN AFTER 04Z. KSFO BRIDGE APPROACH...BRIDGE HAS GONE TO FEW WITH CONTINUED CLEARING THE REST OF THE DAY. NOT EXPECTING CIGS OVER THE APPROACH UNTIL AFTER 05Z. MONTEREY BAY AREA TERMINALS...VFR THE REST OF THE AFTERNOON BUT EARLY RETURN OF CIGS FOR KMRY AND KSNS THIS EVENING. && .MTR WATCHES/WARNINGS/ADVISORIES... .TDAY...SCA...PIGEON PT TO PT PINOS 0-10 NM FROM 5 PM SCA...PT PINOS TO PT PIEDRAS BLANCAS 0-10 NM FROM 2 PM SCA...PIGEON PT TO PT PIEDRAS BLANCAS 10-60 NM FROM 2 PM SCA...SF BAY FROM 2 PM && $$ PUBLIC FORECAST: AC/BLIER AVIATION/MARINE: RWW VISIT US AT WWW.WEATHER.GOV/SANFRANCISCO FOLLOW US ON FACEBOOK, TWITTER, AND YOUTUBE AT: WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.SANFRANCISCOBAYAREA.GOV WWW.TWITTER.COM/NWSBAYAREA WWW.YOUTUBE.COM/NWSBAYAREA  FXUS66 KMTR 301151 AFDMTR AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA 451 AM PDT TUE APR 30 2013 ...A WARM WEEK AHEAD WITH WINDY CONDITIONS IN THE NORTH AND EAST BAY HILLS THIS EVENING THROUGH WEDNESDAY MORNING... ...RED FLAG WARNINGS ISSUED FOR THE NORTH AND EAST BAY HILLS FROM 6 PM TODAY THROUGH 6 PM WEDS... .DISCUSSION...AS OF 3:20 AM PDT TUESDAY...SATELLITE AND SURFACE OBS INDICATE ONLY SOME MINOR POCKETS OF LOW CLOUDS AND PATCHY FOG. RIGHT NOW HALF MOON BAY IS THE ONLY SPOT REPORTING REDUCED VISIBILITIES WHILE MONTEREY NOW HAS A CEILING. DETAILS FROM THE OVERNIGHT SATELLITE FOG PRODUCT ARE A BIT DIFFICULT TO MAKE OUT ALTHOUGH LOOKS LIKE THE AREAS ARE VERY SMALL IN NATURE. NORTHERLY SURFACE FLOW REMAINS AROUND 10 MB WHICH WILL HELP TO GREATLY LIMIT IMPACTS TO ALMOST ALL SPOTS. BOTTOM LINE...OUTSIDE OF JUST A FEW SPOTS...SHOULD BE A MOSTLY SUNNY DAY ACROSS OUR AREA. HIGHS YESTERDAY WERE ABOVE NORMAL IN ALMOST ALL LOCATIONS AND APPROACHED RECORD VALUES IN A FEW AREAS. TODAY SHOULD BE A BIT COOLER AS HEIGHTS AND TEMPERATURES ALOFT DROP IN RESPONSE TO A SHORTWAVE TROF THAT WILL DROP SOUTHWARD FROM CANADA INTO THE NORTHERN ROCKIES. MOST LOCATIONS WILL LOWER 5 DEGREES OR SO COMPARED TO MONDAY -- STILL WARM BUT WELL SHORT OF ALMOST ALL RECORDS. COASTAL AREAS SHOULD SEE MORE OF A MARINE INFLUENCE AS THE WESTERLY GRADIENT WILL BE BETWEEN 1 AND 2 MB FOR MOST OF THE DAY. HIGHS WILL RANGE FROM 60S TO LOWER 70S AT THE COAST TO MID 70S TO MID 80S INLAND. WINDS WILL INCREASE BY LATE THIS AFTERNOON AS A RIDGE OF HIGH PRESSURE AT THE SURFACE BUILDS IN TO OUR NORTH WHICH WILL LEAD TO THE NORTHERLY PRESSURE GRADIENT TO GREATLY INCREASE. BY TONIGHT THE SFO-WMC FORECAST CALLS FOR AN IMPRESSIVE 21 MB WHILE 925 MB SPEEDS ARE EXPECTED TO BE AS STRONG AS 45 KT. WIND ADVISORY REMAINS IN PLACE GOING INTO WEDNESDAY AS GUSTS OVER 50 MPH LOOK LIKELY FOR BOTH THE NORTH AND EAST BAY HILLS. SHOULD BE NOTED THAT ALTHOUGH THE GUIDANCE IS CONCENTRATING MORE ON THE NORTH BAY HILLS...GROUND TRUTH FROM PAST EVENTS SHOWS THAT MANY TIMES THE EAST BAY HILLS SEE WINDS AS STRONG (OR LOCALLY STRONGER). MAIN CONCERN REMAINS FOR POTENTIAL FIRE WEATHER ISSUES, SO THE RED FLAG WARNING WILL CONTINUE. A GENERIC WIND ADVISORY ALSO REMAINS IN PLACES FOR LOCAL GUSTS OF 50 TO 60 MPH. TEMPERATURES WILL INCREASE AGAIN FOR WEDNESDAY THROUGH FRIDAY AS THE RIDGE OF HIGH PRESSURE OUT IN THE PACIFIC BUILDS ACROSS OUR AREA. THERE IS A POTENTIAL WE COULD SEE A FAIR NUMBER OF RECORDS FALLING ON FRIDAY WHEN THE WARMEST AIR ARRIVES (AND MANY RECORD SHOW A SLIGHT DIP FOR THAT DAY). STANDARD DEVIATIONS OF NEARLY 6 ARE FORECAST FOR TEMPERATURES AT 1000 MB WHICH -- IF IT VERIFIES -- WOULD CAUSE A SLEW OF RECORDS TO BE TOPPLED. STILL SOME UNCERTAINTY IF THE WARMTH WILL EXTEND ALL OF THE WAY TO THE COAST OR ENOUGH OF A FLOW OFF THE WATER WILL KEEP THINGS THERE MORE MODERATED. INTERIOR SPOTS DEFINITELY LOOK VERY WARM TO HOT WITH 850 MB READINGS OF 19-21C POSSIBLE. TEMPERATURES WILL COOL BY THE WEEKEND AND INTO NEXT WEEK AS AN UPPER LEVEL LOW MOVES NEAR OUR AREA. 850 MB TEMPS WILL DROP BY AT LEAST 5C AND 500 MB HEIGHTS WILL LOWER FROM 585 DM TO JUST 560 DM. HIGHS AT THE SURFACE WILL BE IN THE 60S AT THE COAST WILL 70S TO LOWER 80S INLAND ON SUNDAY WITH A FEW ADDITIONAL DEGREES OF COOLING LIKELY FOR NEXT WORK WEEK. && .AVIATION...AS OF 4:50 AM PDT TUESDAY...VFR EXCEPT PATCHY MVFR AROUND MRY BAY THROUGH MID MORNING. FT ORD PROFILER SHOWS MARINE LAYER CLIMBING UP TO 1500 FT HOWEVER NORTH SOUTH SFO-ACV GRADIENT REMAINS OVER 9 MB PREVENTING FURTHER STRATUS INTRUSION. VICINITY OF KSFO...VFR THROUGH THE PERIOD. WEST WINDS INCREASING TO 20 TO 25 KT THIS AFTERNOON. KSFO BRIDGE APPROACH...SIMILAR TO KSFO. MONTEREY BAY AREA TERMINALS...SHORT LIVED MVFR THIS MORNING. VIIRS DAY NIGHT SATELLITE AND GOES-R MVFR PROBABILITIES INDICATE CLOUD DECK IS PATCHY. OTHERWISE VFR WITH ONSHORE WINDS. && .FIRE WEATHER...AS OF 3:20 AM TUESDAY...RED FLAG WARNINGS CONTINUE FOR THE NORTH AND EAST BAY HILLS ZONES ABOVE 1000 FEET FROM 6 PM TODAY THROUGH 6 PM WEDNESDAY. ALL OF THE WEATHER FACTORS LINE UP FOR A STRONG RED FLAG EVENT. WILD CARD HAS BEEN THE FUELS WHICH ALL RECENT READINGS SHOW BEING AT OR NEAR RECORD DRY LEVELS FOR LATE APRIL. RED FLAGS IN LATE APRIL OR EARLY MAY ARE ESSENTIALLY UNPRECEDENTED AROUND HERE. HOWEVER WE'VE HAD VERY DRY WEATHER SINCE JANUARY FIRST WITH ABOVE NORMAL TEMPERATURES THE LAST FEW WEEKS IN GENERAL. TEMPERATURES SHOULD COOL A FEW DEGREES TODAY COMPARED TO MONDAY BUT STILL BE ABOVE NORMAL INLAND. A DRY COOL FRONT WILL PASS TO OUR NORTH AND EAST AND INDUCE A VERY STRONG PRESSURE GRADIENT...SIMILAR TO A FALL OFFSHORE WIND EVENT. HOWEVER UNLIKE THE LATE FALL OR WINTER THIS EVENT WILL BE VERY WARM TO HOT. EXPECT MILD TO WARM OVERNIGHT READINGS IN THE HILLS TONIGHT INTO WEDNESDAY WITH HUMIDITY STAYING UNDER 30 PERCENT AND LIKELY AROUND 20 PERCENT. NAM MODEL HAS BEEN VERY CONSISTENT IN SHOWING A SPIKE IN WINDS AT THE 1500-3000 FOOT LEVEL AROUND 06Z (11 PM TUESDAY NIGHT). A SEVERAL HOUR PERIOD OF SUSTAINED NORTHEAST WINDS FROM 20 TO 35 MPH WITH FREQUENT GUSTS TO 50 MPH AND STRONGER GUSTS TO 60 MPH WILL BE STRONG ENOUGH TO BRING DOWN POWER LINES AS WELL AS DROUGHT/DISEASED STRESSED TREES. OBVIOUSLY THE DOWNED LINES COULD SPARK NEW FIRES. HOPING THE RED FLAG WILL INDUCE EXTRA VIGILANCE WITH THE GENERAL PUBLIC FOR THINGS LIKE BARBECUES...WELDING AND SPRING BURNING PROJECTS. && .MTR WATCHES/WARNINGS/ADVISORIES... .TDAY...WIND ADVISORY...NORTH AND EAST BAY HILLS SCA...PT REYES TO PIGEON PT 0-10 NM SCA...PIGEON PT TO PT PINOS 0-10 NM SCA...PT PINOS TO PT PIEDRAS BLANCAS 0-10 NM GLW...PT ARENA TO PIGEON PT 10-60 NM SCA...PT ARENA TO PT REYES 0-10 NM SCA...PIGEON PT TO PT PIEDRAS BLANCAS 10-60 NM && $$ PUBLIC FORECAST: BELL AVIATION/MARINE: AC FIRE WEATHER: BELL/RWW VISIT US AT WWW.WEATHER.GOV/SANFRANCISCO FOLLOW US ON FACEBOOK, TWITTER, AND YOUTUBE AT: WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.SANFRANCISCOBAYAREA.GOV WWW.TWITTER.COM/NWSBAYAREA WWW.YOUTUBE.COM/NWSBAYAREA  FXUS66 KMTR 051153 AFDMTR AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA 453 AM PDT WED JUN 5 2013 .DISCUSSION...AS OF 3:45 AM PDT WEDNESDAY...SATELLITE IMAGERY SHOWS LOW CLOUDS COVERING MOST INLAND AREAS FROM SANTA CRUZ AND ALAMEDA COUNTY NORTHWARD...BUT STRATUS ONLY EXTENDS LOCALLY INTO THE MONTEREY BAY AND SALINAS AND HOLLISTER VALLEYS AT THIS TIME. EXPECT THE LOW CLOUDS TO FILL IN BY DAYBREAK...HOWEVER...AS THE MARINE LAYER REMAINS DEEP...AROUND 2500 FEET PER THE FORT ORD PROFILER. IN ADDITION...THE SURFACE PRESSURE GRADIENT REMAINS TIGHT ONSHORE WITH 3.1 MB FROM SFO TO SAC. TEMPERATURES WILL CONTINUE TO BE COOL TODAY...PERHAPS A FEW DEGREES WARMER IN SPOTS. ADDITIONAL WARMING IS ANTICIPATED FOR THURSDAY AS HIGH PRESSURE ALOFT BEGINS BUILDING OVER CALIFORNIA. THIS UPPER RIDGE IS STILL PROGGED TO BUILD IN FAIRLY STRONGLY OVER THE STATE WITH AN UPPER LOW NESTLED OFF THE SOUTHERN CALIFORNIA COAST. LATEST MODEL RUNS ARE LESS ROBUST WITH THE RIDGE...THUS FORECAST HIGH TEMPERATURES FOR THE AREA ARE A LITTLE LESS HOT THAN FROM PREVIOUS MODEL RUNS...ALTHOUGH STILL VERY WARM. THE LATEST FORECAST ADVERTISES HIGHS ON FRIDAY AND SATURDAY IN THE WARMEST AREAS TO BE IN THE 100-105 RANGE...POSSIBLY A LITTLE WARMER IN THE NORTH BAY MOUNTAINS. NEAR-COASTAL AREAS ARE FORECAST TO REMAIN IN THE 60S...WITH 70S AND 80S AROUND THE BAY. COOLER TEMPS ARE EXPECTED BY SUNDAY AS THE RIDGE BEGINS TO FLATTEN AND THE CUTOFF LOW MOVES EAST. THERE IS STILL A POSSIBILITY FOR CONVECTION TO DEVELOP ON SUNDAY AND MONDAY ACROSS PORTIONS OF THE STATE AS THE UPPER LOW MOVES ACROSS. THE LATEST GFS PAINTS THE MOST UNSTABLE AREAS ACROSS THE NORTHERN PART OF THE STATE. WILL CONTINUE TO MONITOR THIS. OTHERWISE...SEASONABLE TEMPS ARE EXPECTED NEXT WEEK. && .AVIATION...AS OF 4:45 AM PDT WEDNESDAY...MAINLY LOW MVFR TO OCCASIONAL IFR CIGS THROUGH AT LEAST 18Z. A DEEP MARINE LAYER...AROUND 2500 FEET...AND MODERATE ONSHORE FLOW BROUGHT ABUNDANT STRATUS TO THE REGION. THE SYNOPTIC SETUP IS SIMILAR TO YESTERDAY...WITH DISSIPATION FORECAST TO BE NEARLY IDENTICAL TO YESTERDAY MORNING. LOW CONFIDENCE AS ANY SHIFT IN THE UPPER LOW OFF THE SOUTHERN CALIFORNIA COAST MAY HAVE A BIG IMPACT ON THE STRATUS PATTERN. VICINITY OF KSFO...MVFR CIGS THROUGH AT LEAST 18Z. LOW CONFIDENCE. A FEW OF THE SHORT TERM MODELS INDICATE CLEARING A BIT EARLY...BUT WITH STRATUS THICKNESS AROUND 1000 FEET...ACCORDING TO THE GOES W CLOUD THICKNESS PRODUCT...STRATUS WILL LIKELY BE A BIT SLOWER TO DISSIPATE. KSFO BRIDGE APPROACH...PATCHY LOW CLOUDS MAY IMPACT THE APPROACH THROUGH 19Z. MONTEREY BAY AREA TERMINALS...MVFR TO IFR CIGS THROUGH AT LEAST 19Z. MODERATE CONFIDENCE. A FEW OF THE SHORT TERM MODELS INDICATE BRIEF CLEARING WILL OCCUR THIS AFTERNOON...WITH AN EARLY RETURN OF STRATUS. && .MARINE...AS OF 4:50 AM PDT WEDNESDAY...MODEL GUIDANCE IS STILL ON TRACK BRINGING A DECENT LONG PERIOD SOUTH SWELL INTO THE COASTAL WATERS. THE LONGER PERIOD SWELL IS FORECAST TO BE 22-23 SECONDS THIS EVENING/OVERNIGHT AND DROPPING CLOSE TO 20-21 SECONDS ON THURSDAY WITH HEIGHTS 3 TO 4 FT. PERIOD AND SWELL LINGER INTO THE WEEKEND. THE LONG PERIOD SOUTH SWELL WILL ALSO LIKELY CAUSE AN INCREASED THREAT FOR RIP CURRENTS AND LONG SHORE CURRENTS...ESPECIALLY ALONG THE SOUTH FACING BEACHES. && .CLIMATE... RECORD HIGH TEMPERATURES JUNE 7 JUNE 8 ___________________________________________________________________ SANTA ROSA CLIMATE SITE 100 1973 102 1973 KENTFIELD 98 1973 105 1973 SAN RAFAEL 95 1973 104 1973 NAPA CLIMATE SITE 99 1973 102 1973 SAN FRANCISCO DOWNTOWN 85 1979 92 1990 SAN FRANCISCO AIRPORT 89 1979 98 1973 OAKLAND MUSEUM 96 1973 107 1973 OAKLAND AIRPORT 91 1979 94 1973 LIVERMORE 101 1973 106 1918 SAN JOSE 95 1973 102 1973 GILROY 105 1978 102 1973 MONTEREY CLIMATE SITE 80 1973 94 1973 SANTA CRUZ 88 1973 103 1973 SALINAS 84 1973 92 1993 KING CITY 103 1973 107 1973 && .MTR WATCHES/WARNINGS/ADVISORIES... .TDAY...SCA...SF BAY FROM 1 PM && $$ PUBLIC FORECAST: SIMS AVIATION/MARINE: RILEY CLIMATE: RWW VISIT US AT WWW.WEATHER.GOV/SANFRANCISCO FOLLOW US ON FACEBOOK, TWITTER, AND YOUTUBE AT: WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.SANFRANCISCOBAYAREA.GOV WWW.TWITTER.COM/NWSBAYAREA WWW.YOUTUBE.COM/NWSBAYAREA  FXUS66 KMTR 090544 AFDMTR AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA 1044 PM PDT MON JUL 8 2013 .DISCUSSION...AS OF 9:00 PM PDT MONDAY...IT'S CHARACTERISTIC OF A SUMMER EVENING WITH PLENTY OF STRATUS SEEN OVER THE COASTAL WATERS AND CLEAR SKIES INLAND. TEMPERATURES BEHAVED IN A TYPICAL SUMMER FASHION AS WELL WITH HIGHS IN THE 60S COAST-SIDE TO THE LOWER 100S INLAND VALLEYS OVER THE SOUTHERN PORTIONS. BRADLEY'S TEMPERATURE PEAKED AT 103F TODAY. DRY WEATHER IS PRESENTLY ADVERTISED FOR THE REMAINDER OF THE WEEK. HOWEVER DEEPER LAYERED SOUTHERLY WIND FLOW COULD BRIEFLY INTERRUPT THE DRY STRETCH BY WEDNESDAY NIGHT. AT THIS TIME THERE IS ONLY A VERY SMALL CHANCE THAT CONVECTION/AND THUNDER?? COULD DEVELOP WEDNESDAY NIGHT OVER SOUTHERN MONTEREY AND SAN BENITO COUNTIES AS THE MOISTURE AND INSTABILITY REMNANTS FROM TROPICAL CYCLONE "ERICK" MOVE UP FROM THE BAJA PENINSULA AND SOUTHERN CALIFORNIA. OF COURSE IF CONVECTION IS REALIZED THEN CONVECTIVE ELEMENTS COULD MOVE FARTHER NORTH IMPACTING MORE OF THE AREA. IT'S WORTH MENTIONING IT IN DISCUSSION BUT PERHAPS THERE ARE NOT ENOUGH ELEMENTS COMING TOGETHER TO UPDATE THE GRIDS TO INCLUDE THUNDER AT THIS POINT. MID LEVEL DRYING WHICH CAN GREATLY DESTABILIZE AN ASCENDING LAYER DRIVEN BY ATMOSPHERIC DYNAMICS APPEARS TO BE LACKING IN THIS PARTICULAR CASE BUT ON THE OTHER HAND MODEL FORECASTS MAY NOT HAVE THE BEST HANDLE ON THE SITUATION. AS USUAL THERE IS UNCERTAINTY. OTHERWISE HIGH PRESSURE OVER CALIFORNIA WILL GRADUALLY SHIFT EAST AS AN UPPER LEVEL LOW PRESSURE AREA OVER THE EASTERN PACIFIC APPROACHES THE NORTHERN BAY AREA WEDNESDAY AND WEDNESDAY NIGHT. A MODERATE TO DEEP MARINE LAYER AND WEAK ONSHORE WINDS WILL KEEP COASTAL TEMPERATURES COOLER WHILE INLAND TEMPERATURES CLIMB IN TO THE 90S AND FEW LOWER 100S. NO UPDATES TO GRIDS/FORECASTS ARE PLANNED THIS EVENING. && .AVIATION...AS OF 10:44 PM PDT MONDAY...THE CURRENT SATELLITE DERIVED IFR PROBABILITY INDICATES STRATUS PUSHING THROUGH THE GOLDEN GATE THIS EVENING. SCATTERED CONDITIONS ARE BEING REPORTED AT KOAK WITH SFO REPORTING FEW. THE IFR PROBABILITY PRODUCT IS ALSO SHOWING CIGS OVER SALINAS AND JUST BEGINNING TO MOVE IN OVER MONTEREY. STRATUS IS EXPECTED TO CONTINUE TO MOVE ON SHORE OVERNIGHT. VICINITY OF KSFO...VFR CONDITIONS WILL PERSIST THROUGH LATE THIS EVENING. IFR CONDITIONS WILL RETURN TO THE TERMINAL AROUND 1100Z. VFR WILL BE POSSIBLE BY 1700Z. KSFO BRIDGE APPROACH...SIMILAR TO KSFO. MONTEREY BAY AREA TERMINALS...IFR CONDITIONS WILL PERSIST THROUGH 1100Z AT WHICH POINT CONDITIONS WILL DETERIORATE TO LIFR. VFR WILL BE POSSIBLE BY 1700Z. && .MTR WATCHES/WARNINGS/ADVISORIES... .TNGT...NONE. $$ PUBLIC FORECAST: CANEPA AVIATION/MARINE: LARRY VISIT US AT WWW.WEATHER.GOV/SANFRANCISCO FOLLOW US ON FACEBOOK, TWITTER, AND YOUTUBE AT: WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.SANFRANCISCOBAYAREA.GOV WWW.TWITTER.COM/NWSBAYAREA WWW.YOUTUBE.COM/NWSBAYAREA  FXUS66 KMTR 121147 AFDMTR AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA 447 AM PDT FRI JUL 12 2013 .DISCUSSION...AS OF 02:59 AM PDT FRIDAY...MARINE LAYER IN PLACE HAS BROUGHT STRATUS INTO THE SAN FRANCISCO AND MONTEREY BAY AREAS...PUSHING INLAND INTO THE VALLEYS AND TYPICAL LOWER ELEVATION LOCATIONS. AM EXPECTING CLOUD COVER TO BURN-OFF ACROSS INLAND LOCATIONS LATE MORNING/EARLY AFTERNOON. TEMPERATURES WILL BE A FEW DEGREES WARMER TODAY AND INTO THE WEEKEND AS THE WEAK MID/UPPER LEVEL TROUGH AXIS BECOMES ABSORBED IN THE MEAN FLOW AND THE RIDGE OVER THE DESERT SOUTHWEST BECOMES THE DOMINATE FEATURE. WITH A PERSISTENT MARINE LAYER EXPECTED THROUGH MUCH OF THE EXTENDED...OVERNIGHT CONDITIONS WILL NOT CHANGE MUCH FROM NIGHT TONIGHT WITH LOW STRATUS LIKELY. BY MIDWEEK...THE TROUGH OFF THE PACIFIC NORTHWEST WILL STRENGTHEN AND BRING A MORE PREDOMINATE ONSHORE FLOW AND SLIGHTLY COOLER CONDITIONS BACK TO COASTAL LOCATIONS. OVERALL...TYPICAL SUMMER TIME PATTERN WILL REMAIN IN PLACE WITH VERY LITTLE DAY TO DAY VARIATIONS. && .AVIATION...AS OF 4:45 AM PDT FRIDAY...MVFR TO IFR CIGS WILL CONTINUE TO IMPACT THE TERMINAL THROUGH AT LEAST 18Z. MODERATE ONSHORE FLOW WITH A DEEP MARINE LAYER (AROUND 2000 FEET) ALLOWED STRATUS TO MOVE WELL INLAND. CURRENT GOES W CLOUD THICKNESS PRODUCT INDICATES STRATUS IS AROUND 1000 FEET THICK...ALLOWING FOR CLEARING TIMES SIMILAR TO YESTERDAY. OTHERWISE...ONSHORE FLOW WILL INCREASE LATER THIS AFTERNOON...WITH GUSTY WEST WINDS AFTER 21Z. VICINITY OF KSFO...LOW CLOUDS ARE FORECAST TO MOVE OVER THE TERMINAL WITHIN THE NEXT HOUR...WITH CLEARING AROUND 18Z. MODERATE CONFIDENCE. MODERATE WEST WINDS THIS AFTERNOON...WITH GUSTS TO 25 KT. KSFO BRIDGE APPROACH...THE APPROACH WILL BE IMPACTED WITH MVFR CIGS THROUGH AT LEAST 18Z. PATCHES OF STRATUS MAY LINGER OVER THE APPROACH UNTIL 19Z. LOW CONFIDENCE. MONTEREY BAY AREA TERMINALS...IFR CIGS THROUGH 18Z...LIFTING TO MVFR THROUGH 21Z. LOW CONFIDENCE. SHORT TERM MODELS INDICATE THAT KMRY MAY BE IMPACTED BY LOW CLOUDS ALL DAY. OTHERWISE...MODERATE ONSHORE WINDS THIS AFTERNOON WITH AN EARLY STRATUS RETURN. && .MTR WATCHES/WARNINGS/ADVISORIES... .TDAY...SCA...PT ARENA TO PIGEON PT 10-60 NM SCA...PT ARENA TO PT REYES 0-10 NM FROM 5 PM SCA...SF BAY FROM 1 PM && $$ PUBLIC FORECAST: RGASS AVIATION/MARINE: RILEY VISIT US AT WWW.WEATHER.GOV/SANFRANCISCO FOLLOW US ON FACEBOOK, TWITTER, AND YOUTUBE AT: WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.SANFRANCISCOBAYAREA.GOV WWW.TWITTER.COM/NWSBAYAREA WWW.YOUTUBE.COM/NWSBAYAREA  FXUS66 KMTR 231736 AFDMTR AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA 1036 AM PDT WED OCT 23 2013 .DISCUSSION...AS OF 9:14 AM PDT WEDNESDAY...IT IS A FOGGY MORNING AROUND THE SAN FRANCISCO BAY AREA WITH NUMEROUS REPORTS OF DENSE FOG. DEW POINTS ARE RUNNING BETWEEN 45 AND 50 DEGREES WITH DEW POINT DEPRESSIONS AROUND 1 DEGREE. ONCE THE GROUND BEGINS TO WARM WE SHOULD BEGIN TO SEE ATMOSPHERIC MIXING WHICH WILL HELP TO ERODE THE FOG BY LATE MORNING. THE CURRENT RIDGE OF HIGH PRESSURE POSITIONED OVER THE EASTERN PACIFIC IS EXPECTED TO PERSIST INTO THURSDAY. WITH THIS IN MIND EXPECTED SIMILAR FOGGY CONDITIONS FOR THURSDAY MORNING. THEREFORE...WILL BE ISSUING A DENSE FOG ADVISORY WITH THE AFTERNOON FORECAST PACKAGE FOR THE NORTH BAY AREA AND THE SAN FRANCISCO SHORELINE VALID FROM LATE THIS EVENING THROUGH THURSDAY MORNING. THE 0000Z ECMWF AND 1200Z GFS40 HAVE INITIALIZED WELL WITH THE CURRENT SYNOPTIC PATTERN AND REMAIN IN GOOD AGREEMENT WITH CUT OFF LOW DIVING SOUTHEAST TOWARDS THE FORECAST AREA OVER THE NEXT FEW DAYS. THE LOW SHOULD BE CLOSE ENOUGH TO THE COAST FRIDAY TO PROVIDE SOME RELIEF FROM THE FOG. OTHERWISE THIS LOW WILL REMAIN OFFSHORE WITH NO PRECIPITATION EXPECTED FOR THE FORECAST AREA. THE ECMWF AND GFS40 DO SLIDE THE LOW TO THE SOUTHWEST MONDAY AS A TROUGH OF LOW PRESSURE SLIDES IN ALONG THE SIERRA. AS THIS LOW SLIDES INLAND OFFSHORE FLOW MAY DEVELOP OVER THE FORECAST AREA. DRY WEATHER IS EXPECTED TO PERSIST THROUGH THE NEXT SEVEN DAYS. IN FACT THE CLIMATE PREDICTION CENTERS SIX TO TEN DAY OUTLOOK AND THE EIGHT TO FOURTEEN DAY OUTLOOK BOTH DEPICT BELOW NORMAL PRECIPITATION FOR THE WEST COAST. && .AVIATION...AS OF 10:30 AM PDT WEDNESDAY...LOW CLOUDS AND PATCHY FOG ARE SLOW TO DISSIPATE THIS MORNING...AS CLOUD THICKNESS INCREASED SLIGHTLY COMPARED TO 24 HRS AGO. EXPECT VFR CONDITIONS BETWEEN 18 AND 19Z...WITH A FEW ISOLATED LOCATIONS SLIGHTLY AFTER THAT. OTHERWISE...MODERATE ONSHORE FLOW THIS AFTERNOON INTO THE EARLY EVENING HOURS. SIMILAR CONDITIONS ARE EXPECTED TOMORROW AS THE WEATHER PATTERN REMAINS NEARLY STAGNANT...WITH PATCHY DENSE FOG NOT OUT OF THE QUESTION. VICINITY OF KSFO...VFR CONDITIONS BY 1830Z. MODERATE TO LOW CONFIDENCE WITH EXACT TIMING. MODERATE WESTERLY WINDS TO 15 KT THIS AFTERNOON...MAINLY AFTER 22Z. OTHERWISE...EARLY RETURN OF LOW CLOUDS...RIGHT AROUND MIDNIGHT. KSFO BRIDGE APPROACH...SIMILAR TO KSFO. MONTEREY BAY AREA TERMINALS...VFR CONDITIONS EXPECTED AROUND 19Z. MODERATE CONFIDENCE. MODERATE ONSHORE FLOW THIS AFTERNOON WITH A RETURN OF LIFR CIGS BY 02Z. .MTR WATCHES/WARNINGS/ADVISORIES... .TDAY...DENSE FOG ADVISORY...NORTH BAY VALLEYS UNTIL 11 AM. && $$ PUBLIC FORECAST: LARRY AVIATION/MARINE: RILEY VISIT US AT WWW.WEATHER.GOV/SANFRANCISCO FOLLOW US ON FACEBOOK, TWITTER, AND YOUTUBE AT: WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.SANFRANCISCOBAYAREA.GOV WWW.TWITTER.COM/NWSBAYAREA WWW.YOUTUBE.COM/NWSBAYAREA  FXUS66 KMTR 081137 AFDMTR AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA 337 AM PST FRI NOV 8 2013 .DISCUSSION...AS OF 2:18 AM PST FRIDAY...SATELLITE IMAGERY IS SHOWING SOME LOW CLOUDS OVER THE COASTAL WATERS AT THIS TIME WITH SOME PATCHY FOG SHOWING UP IN THE NORTH BAY VALLEYS AS WELL AS AROUND THE SAN FRANCISCO BAY. 24 HOUR TEMPERATURE TRENDS INDICATE COOLER TEMPERATURES THIS MORNING AS THERE IS NO HIGH CLOUD SHIELD. THE DISTRICT WILL BE STARTING OUT COOLER...AND AS THE ONSHORE SURFACE PRESSURE GRADIENT CONTINUES TO TIGHTEN...EXPECT A COOLER DAY TODAY. LITTLE CHANGE IS EXPECTED ON SATURDAY WITH CONTINUED ONSHORE FLOW...BUT TEMPERATURES ARE EXPECTED TO BE AROUND NORMAL FOR THIS TIME OF YEAR. AN UPPER LEVEL LOW PRESSURE SYSTEM IS FORECAST TO DEEPEN OVER THE EASTERN PACIFIC DURING THE WEEKEND AND APPROACH THE COAST BY EARLY NEXT WEEK. THE MOST CURRENT RUNS OF THE MEDIUM RANGE MODELS ALL TRACK THIS SYSTEM MORE TO THE NORTHEAST AS IT MOVES INLAND THUS RAIN CHANCES ARE NOW EXPECTED TO REMAIN MAINLY NORTH OF THE GOLDEN GATE FROM LATE MONDAY NIGHT INTO TUESDAY WITH DRY CONDITIONS SOUTH. HIGH PRESSURE IS THEN FORECAST TO BUILD IN STRONGLY BEHIND THIS SYSTEM THUS DRY AND WARMER CONDITIONS ARE FORECAST FOR THE REMAINDER OF THE WEEK. && .AVIATION...AS OF 3:37 AM PST FRIDAY...FOR 12Z TAFS. PATCHY STRATUS IS APPARENT AROUND THE FORECAST AREA ON THE CURRENT IR SATELLITE FOG PRODUCT. THE GOES-W IFR PROBABILITY PRODUCT ALSO SHOWS PATCHY STRATUS AROUND THE SAN FRANCISCO AND MONTEREY BAY AREAS. THE FORT ORD PROFILER AS WELL AS THE SAN CARLOS PROFILER ARE SHOWING A COMPRESSED MARINE LAYER THIS MORNING. WITH THIS IN MIND ANTICIPATE AN EARLY BURN OFF OF ANY STRATUS IN THE AREA. VICINITY OF KSFO....VFR IS ANTICIPATED TO PREVAIL WITH PASSING CIGS BKN-OVC006 BETWEEN 1200 AND 1700Z. GENERALLY LIGHT WINDS WILL INCREASE TO 8 TO 12 KT THIS AFTERNOON AS THE SEA BREEZE ESTABLISHES ITSELF. KSFO BRIDGE APPROACH...SIMILAR TO KSFO. MONTEREY BAY AREA TERMINALS...VFR IS ANTICIPATED TO PREVAIL AT KSNS TODAY WITH LIFR AT KMRY THIS MORNING IMPROVING TO VFR AROUND 1600Z. GENERALLY LIGHT WINDS WILL INCREASE TO 5 TO 10 KT THIS AFTERNOON AS THE SEA BREEZE ESTABLISHES ITSELF. && .MTR WATCHES/WARNINGS/ADVISORIES... .TDAY...SCA...PIGEON PT TO PT PINOS 0-10 NM FROM 1 PM SCA...PT ARENA TO PIGEON PT 10-60 NM FROM 1 PM SCA...PT PINOS TO PT PIEDRAS BLANCAS 0-10 NM FROM 1 PM SCA...PT ARENA TO PT REYES 0-10 NM FROM 1 PM SCA...PIGEON PT TO PT PIEDRAS BLANCAS 10-60 NM FROM 1 PM SCA...PT REYES TO PIGEON PT 0-10 NM FROM 4 PM && $$ PUBLIC FORECAST: SIMS AVIATION: LARRY VISIT US AT WWW.WEATHER.GOV/SANFRANCISCO FOLLOW US ON FACEBOOK, TWITTER, AND YOUTUBE AT: WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.SANFRANCISCOBAYAREA.GOV WWW.TWITTER.COM/NWSBAYAREA WWW.YOUTUBE.COM/NWSBAYAREA  FXUS66 KMTR 131127 AFDMTR AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA 327 AM PST FRI DEC 13 2013 .DISCUSSION...AS OF 3:12 AM PST FRIDAY...MAIN FORECAST FOCUS THE NEXT SEVERAL DAYS WILL BE ON WARMING TREND OVER THE WEEKEND INTO EARLY NEXT WEEK WITH POTENTIAL FOR NEAR OR RECORD BREAKING WARMTH. IN THE SHORT TERM...WEAK UPPER LEVEL FRONTAL BOUNDARY MOVED THROUGH OVERNIGHT WITH LITTLE FANFARE AS HIGH CLOUDS ARE NOW WELL TO OUR EAST. LOCAL ONSHORE GRADIENTS HAVE TRENDED ONSHORE WITH WEST WINDS NOTED AT THE GOLDEN GATE AND KSFO. PATCHY STRATUS HAS BEEN FORMING OUTSIDE THE GOLDEN GATE AND ALONG THE SAN MATEO COAST WITH HALF MOON BAY REPORTING A 1400 FOOT CEILING. SOME PATCHY STRATUS IS NOW ALSO STARTING TO FORM ON THE EAST SIDE OF THE BAY. FOG IS NOW ALSO BEING REPORTED AT KSTS WITH DENSE FOG AT NOVATO. EXPECT AREAL COVERAGE OF PATCHY CLOUDS TO SLOWLY EXPAND AROUND THE BAY THROUGH SUNRISE. DEWPOINTS HAVE LEVELED OFF AROUND 30 DEGREES WITH OVERNIGHT LOWS GENERALLY IN THE 30S FOR THE VALLEYS AND 40S AROUND THE BAY WHICH REPRESENTS A FEW DEGREES OF WARMING FOR MOST LOCATIONS. RIDGING WILL BUILD THROUGH THIS AFTERNOON WITH MOSTLY SUNNY SKIES AND AFTERNOON TEMPS FROM THE UPPER 50S TO LOWER 60S. UNSEASONABLY STRONG AND WARM HIGH PRESSURE WILL THEN BUILD RIGHT THROUGH THE WEEKEND WITH A FEW DEGREES OF WARMING EACH DAY FROM SATURDAY THROUGH MONDAY. EXPECT TEMPS IN THE 60S AREA WIDE BY SATURDAY THEN WARMING INTO THE MID 60S AND POSSIBLY SOME LOWER 70S BY SUNDAY. IF THE ECMWF IS RIGHT BOTH SUNDAY AND MONDAY HAVE THE POTENTIAL TO AT LAST FLIRT WITH SOME NEAR RECORD WARMTH SHOULD THE OFFSHORE FLOW MATERIALIZE WITH 850 MB TEMPS PROGGED FROM 16-17 CELSIUS. THE GFS AND ECMWF THEN BRING A WEAK CUT-OFF TOWARDS THE COAST BY TUESDAY THAT WOULD BRING A FEW DEGREES OF COASTAL COOLING AND POSSIBLY THE RETURN OF A MARINE STRATUS LAYER OVER THE OCEAN. EITHER WAY DRY AND SEASONABLE WEATHER TUESDAY AND WEDS LOOKS TO BE HIGH CONFIDENCE. BY NEXT THURSDAY THE MODELS BRING A SHORTWAVE DOWN THE SPINE OF THE SIERRA WITH LITTLE OR NO PRECIP FOR THE BAY AREA BUT A NOTED COOLING TREND FOR THE END OF NEXT WEEK. LONG RANGE MODELS REMAIN DRY THROUGH XMAS WEEK AND EVEN NEW YEARS EVE AT THIS TIME...BUT A LOT COULD CHANGE THAT FAR OUT. FOR NOW WEST COAST RIDGE AND EAST COAST TROUGH/COLD PATTERN LOOKS TO STAY MORE OR LESS LOCKED IN. && .AVIATION...AS OF 3:20 AM PST FRIDAY...TRICKY FORECAST THIS MORNING AS WEAK OFFSHORE FLOW PREVAILS...BUT PATCHY STRATUS IS DEVELOPING AROUND THE REGION. LATEST SATELLITE SHOWS MOSTLY CLEAR SKIES...BUT PATCHY LOW CIGS ARE DEVELOPING AROUND SF BAY. IN ADDITION...PATCHY FOG IS NOW DEVELOPING ACROSS THE N BAY VALLEYS. THEREFORE...INCLUDED PATCHY FOG FOR KSTS. LESS CONFIDENCE AROUND SF BAY...BUT DECIDED TO ADD CIGS FOR KOAK SINCE NEARBY CIGS PREVAIL. GOES-R MVFR PROBABILITY INDICATES HIGH PROBABILITY OF MVFR CIGS NEAR KOAK AS OF 3 AM. KSFO WILL ONLY INCLUDE A TEMPO GROUP FOR CIGS THIS MORNING. ELSEWHERE...VFR CONDITIONS PREVAIL. VFR CONDITIONS EXPECTED THIS AFTERNOON. MEDIUM-HIGH CONF. VICINITY OF KSFO...PREVAILING VFR CONDITIONS...BUT WILL HAVE A TEMPO FOR CIGS THROUGH THE MORNING HOURS. VFR THIS AFTERNOON WITH LIGHT ONSHORE FLOW. KSFO BRIDGE APPROACH...A FEW PATCHY CIGS NEAR 1K FT WILL BE POSSIBLE OVER THE APPROACH AND THE S PART OF THE BAY THIS MORNING. OTHERWISE SIMILAR TO KSFO. MONTEREY BAY AREA TERMINALS...EARLIER CIGS DISSIPATED AND WILL KEEP VFR CONDITIONS THROUGH THE PERIOD. WILL HAVE TO MONITOR FOR DEVELOPING CIGS THIS MORNING. && .MTR WATCHES/WARNINGS/ADVISORIES... .TDAY...NONE. $$ PUBLIC FORECAST: RWW AVIATION: MM VISIT US AT WWW.WEATHER.GOV/SANFRANCISCO FOLLOW US ON FACEBOOK, TWITTER, AND YOUTUBE AT: WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.SANFRANCISCOBAYAREA.GOV WWW.TWITTER.COM/NWSBAYAREA WWW.YOUTUBE.COM/NWSBAYAREA  FXUS66 KMTR 142247 AFDMTR AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA 247 PM PST SAT DEC 14 2013 .DISCUSSION...AS OF 2:45 PM PST SATURDAY...SATELLITE IMAGE STILL SHOWS FOG ALONG THE COAST FROM POINT REYES NORTH. SURFACE HIGH PRESSURE IS OFF THE NORTHERN CALIFORNIA COAST SO PATCHY FOG IS POSSIBLE AT THE COAST TONIGHT FROM THE SAN MATEO COAST NORTH. THE FOG DEPTH IS VERY SHALLOW SO FOG WILL BE LOCALLY DENSE. A STRONGER SURFACE HIGH OVER THE GREAT BASIN WILL KEEP FOG AWAY FROM THE INLAND AREAS. TEMPERATURES ARE RUNNING A FEW DEGREES WARMER THAN YESTERDAY AS UPPER LEVEL HIGH PRESSURE OFF THE CALIFORNIA COAST MOVES TOWARDS THE DISTRICT. THE UPPER HIGH WILL MOVE DIRECTLY OVER THE AREA SUNDAY AND MONDAY RESULTING IN A FEW MORE DEGREES OF WARMING EACH DAY. THE SURFACE HIGH OFF THE COAST WEAKENS ON SUNDAY AND THE GREAT BASIN SURFACE HIGH WILL BECOME THE DOMINANT FEATURE SO PATCHY FOG IS NOT EXPECTED AFTER TONIGHT. BY MIDWEEK AN UPPER LEVEL TROUGH WILL SWOOP DOWN FROM THE PACIFIC NORTHWEST AND BY THURSDAY IT WILL FORM INTO A CUTOFF LOW OVER SOUTHERN CALIFORNIA. THIS SYSTEM WILL BE AN INSIDE SLIDER SO RAIN CHANCES FROM THIS SYSTEM WILL BE VERY LOW AS IT MOVES THROUGH THE AREA WEDNESDAY NIGHT. TEMPERATURES WILL BECOME COOLER SIGNIFICANTLY WEDNESDAY AND THURSDAY. LONG RANGE INDICATES UPPER LEVEL HIGH DOMINATING OFF THE CALIFORNIA COAST NEXT WEEKEND SO IT WILL BE CONTINUED DRY WITH ABOVE NORMAL TEMPERATURES. && .AVIATION...AS OF 9:15 AM PST SATURDAY...OFFSHORE FLOW WILL KEEP CONDITIONS VFR TODAY. SOME LOCAL FOG EXPECTED NEAR SANTA ROSA LATE TONIGHT OTHERWISE VFR. LIGHT WINDS. VICINITY OF KSFO...VFR THROUGH THE PERIOD WITH LIGHT WINDS. KSFO BRIDGE APPROACH...SAME AS KSFO. MONTEREY BAY AREA TERMINALS...VFR. LIGHT WINDS. && .MARINE...AS OF 3:20 AM PST SATURDAY...MAIN CONCERN THROUGH THE FORECAST PERIOD WILL BE LONG PERIOD WESTERLY SWELL IMPACTING THE COAST. FORERUNNER WAVES ARE EXPECTED TO ARRIVE EARLY SUNDAY MORNING 3 TO 5 FT WITH A PERIOD OF 18 TO 20 SECONDS AND THEN BUILD 7 TO 9 FEET WITH A PERIOD OF 16-17 SECOND SUNDAY AND MONDAY. AS A RESULT...THIS WILL RESULT IN LARGE BREAK WAVES ALONG POINT BREAKS AND SNEAKER WAVES ON STEEP BEACHES. PERSONS VENTURING TO THE COAST/BEACH SUNDAY SHOULD USE CAUTION. NEVER TURN YOUR BACK ON THE OCEAN. && .MTR WATCHES/WARNINGS/ADVISORIES... .TNGT...NONE. && $$ PUBLIC FORECAST: W PI AVIATION: SIMS VISIT US AT WWW.WEATHER.GOV/SANFRANCISCO FOLLOW US ON FACEBOOK, TWITTER, AND YOUTUBE AT: WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.SANFRANCISCOBAYAREA.GOV WWW.TWITTER.COM/NWSBAYAREA WWW.YOUTUBE.COM/NWSBAYAREA  FXUS66 KMTR 201131 AFDMTR AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA 331 AM PST MON JAN 20 2014 .DISCUSSION...AS OF 3:31 AM PST MONDAY...THE MARINE LAYER HAS RETURNED ALONG THE BIG SUR COAST WITH PATCHES OF FOG AROUND THE MONTEREY PENINSULA. GOES-W CLOUD THICKNESS IMAGERY SUGGESTS...NOT SURPRISINGLY THAT THE CLOUD DECK IS SHALLOW AND UNDER 1000 FEET. HAVE ADDED FOG TO THE COASTAL WATERS AND IMMEDIATE BIG SUR/MONTEREY BAY COASTLINE THIS MORNING. THE PRESENCE OF THE MARINE LAYER ALONG THE COAST WILL BRING SOME COOLING TO THE IMMEDIATE COAST BUT ALL AREAS AWAY FROM THE COAST WILL SEE ANOTHER SUNNY AND SEASONABLY WARM DAY. YESTERDAY KSFO MISSED A RECORD HIGH BY ONE DEGREE AND ONCE AGAIN TODAY WE SHOULD FLIRT WITH SOME RECORDS BUT LIKELY FALL A FEW DEGREES SHORT. ITS ASTONISHING THE NUMBER OF DAYS WE'VE BEEN IN RECORD TERRITORY THIS MONTH...AS THOUGH ITS BECOMING THE NEW NORMAL. RECORDS AT KSFO GO BACK TO 1927 AND THE RECORD FOR TODAY IS 67 DEGREES. BOTH THE LATEST GFS AND NAM MOS GUIDANCE ARE FORECASTING A HIGH OF 66 AS WELL AS OUR OFFICIAL FORECAST. SIMILAR TRENDS ARE SEEN AT NAPA AND LIVERMORE WITH MOS GUIDANCE WITHIN A DEGREE OF RECORD WARMTH...NORMALS FOR THIS TIME OF YEAR ARE THE MID 50S. THE PRESENCE OF THE MARINE LAYER ALONG THE COAST WILL BE WORTH WATCHING BUT NO STRONG EVIDENCE THAT IT WILL BE ABLE TO DEEPEN BEYOND PLACES LIKE HALF MOON BAY OR MONTEREY THE NEXT SEVERAL DAYS. THE SYNOPTIC PATTERN WONT CHANGE MUCH FOR TUESDAY SO EXPECTING SIMILAR WEATHER ONCE AGAIN...PERHAPS A 1-3 DEGREE COOLING TREND. TEMPERATURES WILL SPIKE AGAIN BY MIDWEEK WITH MORE RECORD OR NEAR RECORD WARMTH POSSIBLE WEDS AFTERNOON AS HIGH PRESSURE BUILDS AND 850 MB TEMPS REACH 14-15 CELSIUS. THE NEXT WEATHER CHANGE OF NOTE WILL OCCUR LATE WEDS NIGHT INTO THURSDAY MORNING AS A STRONG SHORTWAVE MOVES INTO NEVADA. PRETTY SOLID AGREEMENT THAT A MODERATE TO STRONG WIND EVENT WILL SET UP OVER THE BAY AREA (AS WELL AS THE SIERRA). ROUGHLY FROM 06-18Z THURSDAY A STRONG SURFACE PRESSURE GRADIENT WILL SET-UP (OFFSHORE) WITH FAVORABLE COOL ADVECTION AND DOWNWARD MOMENTUM. SINCE WERE STILL 72 HOURS OUT HAVE NOT ISSUED ANY WATCHES BUT EARLIER WEATHER STORY GRAPHIC WAS FOLLOWED UP WITH A HAZARDOUS WEATHER OUTLOOK. POTENTIAL IS THERE TO ISSUE A HIGH WIND WATCH THAT COULD BE CONVERTED TO AN ADVISORY OR WARNING WITH OTHER CONCERN FOR FIRE WEATHER IMPLICATIONS AND POSSIBLE FIRE WEATHER WATCH. THE 00Z ECMWF CAME IN AND THREW A WRENCH IN THE FORECAST AS IT CIRCULATES THE LOW BACK OVER THE BAY AREA AND THEN NORTHWARD. NONE OF THE OTHER MODELS SHOW THIS SOLUTION BUT IT CANT BE DISCOUNTED. IF THE ECMWF WOULD VERIFY THE UPPER LOW WOULD BRING COOLER TEMPS...HIGHER HUMIDITY AND THE WINDS ALOFT WOULD BE LESS FAVORABLE FOR STRONG WINDS. WE'VE STILL GOT TIME ON OUR SIDE TO GET SOME BETTER MODEL CONSISTENCY AND DON'T WANT TO OVER-HYPE THIS FAR OUT. ANY STRONG WINDS WILL EASE BY THE WEEKEND WITH A RETURN OF DRY AND MILD WEATHER. IN TERMS OF RAINFALL...THE ECMWF HAS BEEN CONSISTENT FOR 3 STRAIGHT RUNS IN BRINGING A COLD FRONT INTO NORTHERN CALIFORNIA LATE ON THE 27TH OR EARLY JAN 28TH. THE GEM HAS THE SAME FEATURE BUT WEAKER AND FARTHER NORTH WITH GFS STILL TRYING TO GET ON BOARD. SOME OPTIMISM THAT THE ECMWF IS SHOWING CONSISTENCY BUT OVERALL LONG TERM GUIDANCE STILL SHOWS NO SIGNIFICANT PATTERN CHANGE. && .AVIATION...AS OF 10:00 PM PST SUNDAY...A LOW CEILING AND VISIBILITY BRIEFLY AFFECTED KSNS THIS EVENING BUT HAVE SINCE MOVED OUT. OTHERWISE VFR AND LIGHT WINDS ARE REPORTED AT AREA TERMINALS. WRF MODEL SHOWS SOME LOW CLOUDS RETURNING TO THE MONTEREY BAY AREA MONDAY EVENING AND OVERNIGHT. IN FACT IT SHOWS LOW CLOUDS MOVING NORTH TO SAN MATEO COAST AND SAN FRANCISCO LATER AT NIGHT MONDAY. VICINITY OF KSFO...VFR. KSFO BRIDGE APPROACH...VFR. MONTEREY BAY AREA TERMINALS...VFR. && .FIRE WEATHER...AS OF 3:31 AM MONDAY...BY THURSDAY MORNING A WELL PRONOUNCED SHORTWAVE WILL DIVE DOWN OVER EASTERN NEVADA AND INDUCE A STRONG PRESSURE GRADIENT OVER THE SIERRA. TEMPERATURES ALOFT WILL COOL ON THURSDAY IN ASSOCIATION WITH THIS FEATURE...HOWEVER WINDS WILL BECOME NORTHEAST/EAST WITH SOME AMOUNT OF ADIABATIC COMPRESSION OFF-SETTING THE COOLING ALOFT. AS THE SHORTWAVE DIVES TOWARDS THE FOUR-CORNERS THERE IS DECENT AGREEMENT THAT SOME OF THE ENERGY GETS SHEARED OFF INTO SOME TYPE OF UPPER LOW OVER CENTRAL AND SOUTHERN CALIFORNIA. ALL INDICATIONS ARE THAT THE SYSTEM WILL REMAIN DRY. THIS TYPE OF SOLUTION WASN'T INDICATED DAYS AGO BUT NOW THE MODELS ARE SETTLING IN ON THIS PATTERN. THE SET-UP IS SIMILAR TO WHAT OCCURRED NOVEMBER 21-22 OF 2013...JUST BEFORE THANKSGIVING WHEN A PRONOUNCED EASTERLY WIND FLOW SET-UP OVER THE NORTH AND EAST BAY WITH NUMEROUS TREES DOWN AND FIRE STARTS OVER THE NORTH BAY. TOO EARLY TO PREDICT THOSE TYPE OF DETAILS BUT THE PATTERN IS SIMILAR WITH A POTENTIALLY PROLONGED PERIOD OF EASTERLY WINDS IN THE HILLS THURSDAY THROUGH FRIDAY AND POSSIBLY EVEN SATURDAY WITH WINDS SUPPORTED BY PRESSURE GRADIENTS AS WELL AS DYNAMICS ALOFT. WILL NEED TO MONITOR FOR POSSIBLE FIRE WEATHER IMPLICATIONS. && .CLIMATE... RECORD HIGH TEMPERATURES FOR MONDAY 1/20/14. CITY MONDAY 1/20/14 1/21/14 1/22/14 -------------------------------------------------------------------- KENTFIELD 67 IN 1945 68/1939 67/2011 SAN RAFAEL 70 IN 1976 71/1976 75/1968 NAPA 73 IN 1976 71/1988 80/1968 SAN FRANCISCO 69 IN 2009 71/1976 74/1968 SFO AIRPORT 67 IN 1976 67/1976 71/1968 OAKLAND DT 71 IN 1976 67/2007 67/2013 OAKLAND AP 67 IN 2011 69/2007 74/1968 RICHMOND 69 IN 1976 68/1976 69/1974 LIVERMORE 70 IN 1919 73/1919 75/1948 MOUNTAIN VIEW 70 IN 2009 70/1975 72/1968 SAN JOSE 72 IN 2009 71/1950 72/2011 GILROY 77 IN 1994 75/2009 72/1989 MONTEREY 78 IN 1976 76/1976 74/1968 SANTA CRUZ 80 IN 1976 76/1976 77/1968 SALINAS 80 IN 2009 80/1976 80/1968 SALINAS AP 79 IN 1968 75/1975 80/1968 KING CITY 81 IN 1976 78/1976 MISSING && .MTR WATCHES/WARNINGS/ADVISORIES... .TDAY...NONE. $$ PUBLIC FORECAST: RWW AVIATION: CANEPA FIRE WEATHER: RWW CLIMATE: CANEPA VISIT US AT WWW.WEATHER.GOV/SANFRANCISCO FOLLOW US ON FACEBOOK, TWITTER, AND YOUTUBE AT: WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.SANFRANCISCOBAYAREA.GOV WWW.TWITTER.COM/NWSBAYAREA WWW.YOUTUBE.COM/NWSBAYAREA  FXUS66 KMTR 301145 AFDMTR AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA 345 AM PST FRI JAN 30 2015 .SYNOPSIS...DRY CONDITIONS ARE EXPECTED TO CONTINUE INTO NEXT WEEK WITH CHANCES OF RAIN ONLY OVER FAR NORTHERN CALIFORNIA. TEMPERATURES WILL REMAIN SEVERAL DEGREES ABOVE NORMAL FOR THE NEXT WEEK. && .DISCUSSION...AS OF 3:14 AM PST FRIDAY...STRATUS IS SETTING UP ALONG THE COAST AND STARTING TO PUSH INTO THE BAY AREA. CURRENTLY THE AREAS PICKING UP FOG ARE LIMITED TO THE NORTH BAY VALLEYS...BUT EXPECT PATCHY FOG IN MORE PLACES BY MORNING. CURRENT TEMPERATURES ARE RUNNING MAINLY IN THE 40S ACROSS THE DISTRICT EXCEPT AROUND SFO AND ON PENINSULA WHERE LOWER 50S ARE OCCURRING. HIGHS TODAY ARE EXPECTED TO BE IN THE 60S TO LOWER 70S. TONIGHT WHEN AN UPPER LOW NOW OVER SOCAL MOVES TO THE EAST...A SURFACE HIGH WILL MOVE OVER THE NORTHERN GREAT BASIN WHICH WILL INCREASE NORTHERLY WINDS OVER THE HILLS. THE LATEST NAM12 INCREASES 925MB WINDS TO AROUND 30 KNOTS OVERNIGHT TONIGHT AND SATURDAY MORNING MAINLY OVER THE NORTH AND EAST BAY HILLS. MEANWHILE...NORTHERN CALIFORNIA REMAINS UNDER A STAGNANT WEATHER PATTERN WITH AN UPPER RIDGE NOSING INTO THE PACIFIC NORTHWEST AND OVER NORTHERN CALIFORNIA. THE HIGH PRESSURE RIDGE WILL CONTINUE TO SHUNT ALL RAIN CHANCES WELL NORTH OF OUR DISTRICT THROUGH THE FORECAST PERIOD. IN ADDITION...HIGH TEMPERATURES ARE EXPECTED TO BE ABOVE NORMAL THROUGH THE PERIOD. MEDIUM RANGE MODELS CONTINUE TO HOLD ONTO SOME HOPE FOR RAIN POSSIBLY SPREADING INTO NORTHERN CALIFORNIA BY LATE NEXT WEEK. BOTH THE ECMWF AND GFS BRING RAIN TO NORTHERN CALIFORNIA BEGINNING NEXT FRIDAY AND SATURDAY. THE GEM...HOWEVER...KEEPS THE RIDGE INTACT FOR CONTINUED DRY CONDITIONS FOR NORTHERN CALIFORNIA. && .AVIATION...AS OF 3:45 AM PST FRIDAY...THE CURRENT SATELLITE FOG PRODUCT IS SHOWING STRATUS ALONG THE COAST AND IN SAN FRANCISCO BAY THIS MORNING. THE GOES-W LIFR PROBABILITY PRODUCT IS ALSO INDICATING A HIGH PROBABILITY OF STRATUS IN SAN FRANCISCO BAY...STRETCHING SOUTH INTO THE SANTA CLARA VALLEY. VICINITY OF KSFO...IFR CONDITIONS ARE EXPECTED TO IMPACT THE TERMINALS BEGINNING AROUND 1400Z BURNING OFF AROUND 1800Z. WEST WINDS ARE EXPECTED TO INCREASE TO 15 KT WITH THE AFTERNOON SEA BREEZE. CONFIDENCE IS MODERATE. KSFO BRIDGE APPROACH...SIMILAR TO KSFO. MONTEREY BAY AREA TERMINALS...LIFR TO IFR CONDITIONS ARE ANTICIPATED TO PREVAIL THROUGH AROUND 1700Z THIS MORNING. VFR IS THEN ANTICIPATED THROUGH 0200Z AT KMRY AND 0500Z AT KSNS. THE SEA BREEZE IS EXPECTED TO REACH 5 TO 10 KT THIS AFTERNOON. CONFIDENCE IS MODERATE. && .MARINE...AS OF 2:37 AM PST FRIDAY...A THERMAL TROUGH WILL MAINTAIN MODERATE NORTHERLY WINDS ACROSS THE COASTAL WATERS TODAY INTO SATURDAY. THE STRONGEST WINDS ARE EXPECTED TO OCCUR OVER THE OUTER COASTAL WATERS. THESE WINDS WILL RESULT IN CHOPPY SEA CONDITIONS. WIND AND SEA CONDITIONS ARE EXPECTED TO IMPROVE SATURDAY AS THE THERMAL TROUGH WEAKENS...LIGHT WINDS ARE THEN ANTICIPATED TO PREVAIL INTO THE BEGINNING OF NEXT WEEK. && .MTR WATCHES/WARNINGS/ADVISORIES... .TDAY...SCA...PT ARENA TO PT REYES 10-60 NM SCA...PT REYES TO PIGEON PT 10-60 NM SCA...PIGEON PT TO PT PINOS 10-60 NM SCA...PT PINOS TO PT PIEDRAS BLANCAS 10-60 NM && $$ PUBLIC FORECAST: SIMS AVIATION/MARINE: LARRY VISIT US AT WEATHER.GOV/SANFRANCISCO FOLLOW US ON FACEBOOK, TWITTER, AND YOUTUBE AT: WWW.FACEBOOK.COM/NWSBAYAREA WWW.TWITTER.COM/NWSBAYAREA WWW.YOUTUBE.COM/NWSBAYAREA  FXUS66 KMTR 261204 AFDMTR AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA 404 AM PST THU FEB 26 2015 .SYNOPSIS...DRY AND MILD WEATHER CONDITIONS WILL CONTINUE TODAY AS HIGH PRESSURE REMAINS OFF OF THE WEST COAST. A STORM SYSTEM WILL THEN BRING SHOWERS AND COOLER TEMPERATURES TO THE AREA FRIDAY THROUGH THE WEEKEND. ANOTHER WEAK SYSTEM WILL BRING ADDITIONAL SHOWER CHANCES TO THE AREA ON MONDAY. && .DISCUSSION...AS OF 3:16 AM PST THURSDAY...SATELLITE SHOWS ONLY A FEW AREAS OF STRATUS AND FOG AFFECTING INLAND AREAS...MAINLY THE SALINAS VALLEY AND THE NORTH BAY VALLEYS. THE SURFACE PRESSURE GRADIENTS AFFECTING THE AREA ARE MAINLY NORTHERLY...WITH 6.5 MB FROM ACV TO SFO...AND TEMPERATURE TRENDS ARE WARMER THAN YESTERDAY AT THIS TIME BY SEVERAL DEGREES AT MOST LOCATIONS. TODAY IS EXPECTED TO BE ANOTHER MILD DAY WITH 60S AND 70S FOR HIGHS. MEANWHILE...AN UPPER LEVEL LOW IS PROGGED TO SKIRT THE BC COAST AND THEN MOVE INLAND OVER OREGON ON FRIDAY. THIS UPPER LOW IS THEN FORECAST TO DIG SOUTHWARD...AND THEN WESTWARD OVER THE BAY AREA DURING THE WEEKEND. THIS WILL INITIATE SHOWER CHANCES FOR THE AREA AS WELL AS BRING IN COOLER TEMPERATURES. THE PROXIMITY OF THE UPPER LOW WILL ALSO ADD THE POSSIBILITY OF THUNDERSTORMS TO MAINLY THE SOUTHERN PORTION OF THE DISTRICT SATURDAY AND SATURDAY NIGHT. MOISTURE IS LIMITED WITH THIS SYSTEM SO RAINFALL AMOUNTS ARE EXPECTED TO BE LIGHT...UNDER A QUARTER OF AN INCH EXCEPT POSSIBLY UP TO ONE-HALF INCH IN SOME LOCALLY MODERATE SHOWERS. IT WILL BE BREEZY ESPECIALLY NEAR THE COAST BUT WIND ADVISORIES ARE NOT EXPECTED. SNOW LEVELS WILL TO DROP TO AROUND 4000 FEET BY SATURDAY NIGHT SO IF THERE ARE ANY SHOWERS LEFT BY THEN THERE COULD BE A DUSTING OF SNOW ON THE HIGHEST MOUNTAINS. PARTLY CLOUDY SKIES WITH A FEW RESIDUAL SHOWERS ACROSS THE SOUTH ARE EXPECTED SUNDAY AS THE LOW MOVES INTO SOUTHERN CALIFORNIA. ANOTHER WEAKER SYSTEM IS FORECAST TO MOVE DOWN THE WEST COAST ON MONDAY FOR ADDITIONAL RAIN CHANCES. THE MAIN LOW CENTER WITH THIS SYSTEM IS PROGGED TO BE FARTHER EAST...THUS LESS RAIN IS EXPECTED FOR OUR AREA. COOLER TEMPERATURES ARE EXPECTED THROUGH EARLY NEXT WEEK. && .AVIATION...AS OF 4:03 AM PST THURSDAY...CURRENTLY THE IR SATELLITE IMAGE IS SHOWING HIGH CLOUDS PASSING OVER CALIFORNIA. THE EXPERIMENTAL GOES IFR PROBABILITY IMAGE IS SHOWING LOW CLOUDS BANKED ALONG THE SAN FRANCISCO AND SAN MATEO COUNTY COAST AS WELL AS OVER THE MONTEREY PENINSULA. THERE IS ALSO SOME INDICATION OF STRATUS IN SAN FRANCISCO BAY THIS MORNING. COMPARED TO YESTERDAY THE NORTH TO SOUTH SURFACE PRESSURE GRADIENT IS MUCH STRONGER...WHICH SHOULD HELP TO MIX THE STRATUS OUT OF THE SAN FRANCISCO BAY AREA IF IT DOES FORM OVER THE TERMINALS. OTHERWISE THE MAIN IMPACT OF THE DAY WILL BE GUSTY WESTERLY WINDS THIS AFTERNOON. VICINITY OF KSFO...VFR IS ANTICIPATED TO PREVAIL TODAY WITH A SLIGHT CHANCE OF STRATUS BKN012 PASSING OVER THE TERMINAL BETWEEN 1400 AND 1600Z. WESTERLY WINDS WILL INCREASE TO 12 TO 18 KT THIS AFTERNOON WITH GUSTS TO 26 KT. CONFIDENCE IS MODERATE. KSFO BRIDGE APPROACH...SIMILAR TO KSFO. MONTEREY BAY AREA TERMINALS...STRATUS WILL BE IN THE VICINITY THIS MORNING IMPACTING KSNS THROUGH 1600Z AND POTENTIALLY IMPACTING KMRY BETWEEN 1200 AND 1600Z. ONCE THE STRATUS BURNS OFF VFR IS ANTICIPATED THROUGH LATE EVENING. WESTERLY WINDS ARE EXPECTED TO REACH 10 TO 15 KT THIS AFTERNOON WITH GUSTS TO 20 KT POSSIBLE. CONFIDENCE IS MODERATE. && .MARINE...AS OF 2:39 AM PST THURSDAY...A STRENGTHENING SURFACE PRESSURE GRADIENT POSITIONED ALONG THE CALIFORNIA COAST WILL PROMOTE GUSTY NORTHERLY WINDS ACROSS THE COASTAL WATERS. THE GUSTY WINDS WILL PRODUCE LOCALLY HAZARDOUS CONDITIONS WITH STEEP WIND WAVES AND FRESH SWELL. WINDS WILL REMAIN GUSTY INTO THE THE WEEKEND. AN APPROACHING STORM SYSTEM WILL BRING A CHANCE OF SHOWERS TO THE REGION FRIDAY AND SATURDAY. && .MTR WATCHES/WARNINGS/ADVISORIES... .TDAY...SCA...PIGEON PT TO PT PINOS 0-10 NM FROM 4 PM SCA...PT ARENA TO PT REYES 10-60 NM SCA...PT REYES TO PIGEON PT 10-60 NM SCA...PIGEON PT TO PT PINOS 10-60 NM SCA...PT PINOS TO PT PIEDRAS BLANCAS 10-60 NM SCA...PT ARENA TO PT REYES 0-10 NM SCA...PT REYES TO PIGEON PT 0-10 NM SCA...PT PINOS TO PT PIEDRAS BLANCAS 0-10 NM && $$ PUBLIC FORECAST: SIMS AVIATION/MARINE: LARRY VISIT US AT WEATHER.GOV/SANFRANCISCO FOLLOW US ON FACEBOOK, TWITTER, AND YOUTUBE AT: WWW.FACEBOOK.COM/NWSBAYAREA WWW.TWITTER.COM/NWSBAYAREA WWW.YOUTUBE.COM/NWSBAYAREA  FXUS66 KMTR 271202 AFDMTR AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA 402 AM PST FRI FEB 27 2015 .SYNOPSIS...A STORM SYSTEM WILL BRING SHOWERS AND COOLER TEMPERATURES TO THE AREA TOMORROW THROUGH THE WEEKEND. ANOTHER WEAK SYSTEM WILL BRING ADDITIONAL SHOWER CHANCES TO THE AREA ON MONDAY. && .DISCUSSION...AS OF 3:28 AM PST FRIDAY...SURFACE PRESSURE GRADIENTS HAVE SWITCHED MORE TO ONSHORE OVER THE PAST 24 HOURS...AND DEW POINT AND AMBIENT TEMPERATURES HAVE INCREASED BY AS MANY AS 10 DEGREES FROM YESTERDAY AT THIS TIME. SATELLITE IMAGERY SHOWS PARTLY CLOUDY SKIES OVER THE DISTRICT. EXPECT CLOUDS TO INCREASE AS AN UPPER LEVEL LOW APPROACHES THE STATE FROM THE NORTH. THIS LOW WILL BRING IN COLDER AIR ALOFT AND A SLIGHT CHANCE OF SHOWERS TO THE AREA LATER TODAY. SHOWER CHANCES WILL INCREASE FRIDAY NIGHT AND SATURDAY WHEN THE UPPER LOW MOVES OVER THE CENTRAL COAST. THIS WILL ALSO DESTABILIZE THE ATMOSPHERE FURTHER FOR A SLIGHT CHANCE OF THUNDERSTORMS SATURDAY AFTERNOON AND EVENING. SHOWER CHANCES DECREASE SATURDAY NIGHT AS THE LOW MOVES INTO SOUTHERN CALIFORNIA. BY THIS TIME SNOW LEVELS WILL LOWER TO 4000 FEET SO IF THERE ARE ANY SHOWERS LEFT BY THEN THERE COULD BE A DUSTING OF SNOW ON THE HIGHEST MOUNTAINS. TOTAL RAINFALL AMOUNTS WILL BE MEAGER...GENERALLY A QUARTER OF AN INCH OR LESS...ALTHOUGH AMOUNTS COULD BE HIGHER ALONG THE SANTA CRUZ AND MONTEREY COUNTY COAST AND MOUNTAINS WHERE OVER A HALF INCH IS POSSIBLE IN LOCALLY HEAVIER SHOWERS. PARTLY CLOUDY SKIES WITH COOL CONDITIONS ARE EXPECTED ON SUNDAY BEFORE A SECOND SYSTEM APPROACHES FROM THE NORTH. THIS WILL BRING ANOTHER CHANCE OF SHOWERS TO THE AREA MONDAY AND MONDAY NIGHT WITH CONTINUED COOL TEMPERATURES. THIS SYSTEM IS EXPECTED TO MOVE THROUGH QUICKLY WITH SHOWERS ENDING ON TUESDAY. HIGH PRESSURE WILL THEN BUILD BACK IN OVER THE WEST BY MIDWEEK FOR A WARMING AND DRYING TREND THROUGH THE REST OF THE WEEK. && .AVIATION...AS OF 4:02 AM PST FRIDAY...CURRENTLY THE IR SATELLITE IMAGE IS SHOWING SOME HIGH CLOUDS PASSING OVER THE WEST COAST. THE GOES MVFR PROBABILITY PRODUCT IS INDICATING CIGS ALONG THE COAST AND IN THE SANTA CLARA VALLEY. THE SURFACE PRESSURE GRADIENT IS WEAKER THAN IT WAS AT THIS HOUR YESTERDAY BUT AN APPROACHING STORM SYSTEM SHOULD PROVIDE ENOUGH MIXING TO PREVENT WIDESPREAD STRATUS FROM FORMING IN THE SAN FRANCISCO BAY AREA. STRATUS IS APPARENT IN THE MONTEREY BAY AREA BUT SHOULD LIFT AS THE STORM SYSTEM MOVES CLOSER TO THE AREA. VICINITY OF KSFO...VFR IS ANTICIPATED TO PREVAIL TODAY WITH SCT025 PASSING OVER THE TERMINALS AND APPROACH THROUGHOUT THE DAY TODAY. STRONG WEST WINDS ARE EXPECTED TO REACH 25 TO 30 KT THIS AFTERNOON WITH GUSTS TO 38 KT. CONFIDENCE IS MODERATE. KSFO BRIDGE APPROACH...SIMILAR TO KSFO. MONTEREY BAY AREA TERMINALS...MVFR CIGS BKN-OVC015 ARE ANTICIPATED TO LIFT TO BKN035 LATER THIS MORNING AS A STORM SYSTEM APPROACHES THE FORECAST AREA. WEST WINDS WILL INCREASE TO 15 KT THIS AFTERNOON WITH GUSTS TO 25 KT. CONFIDENCE IS MODERATE. && .MARINE...AS OF 2:40 AM PST FRIDAY...GUSTY NORTHWESTERLY WINDS WILL PERSIST TODAY AHEAD OF AN APPROACHING PACIFIC STORM SYSTEM...RESULTING IN POOR SEA CONDITIONS. THE STORM SYSTEM WILL BRING A POSSIBILITY OF SHOWERS AND THUNDERSTORMS TO THE COASTAL WATERS BEGINNING THIS AFTERNOON LASTING INTO SATURDAY EVENING. WINDS WILL DECREASE AND SEA CONDITIONS WILL IMPROVE FOR A MAJORITY OF THE WATERS BY SATURDAY AFTERNOON AS THE CENTER OF THE STORM SYSTEM PASSES ALONG THE CALIFORNIA COAST. && .MTR WATCHES/WARNINGS/ADVISORIES... .TDAY...SCA...PT ARENA TO PT REYES 0-10 NM SCA...PT REYES TO PIGEON PT 0-10 NM SCA...PIGEON PT TO PT PINOS 0-10 NM SCA...PT ARENA TO PT REYES 10-60 NM SCA...PT REYES TO PIGEON PT 10-60 NM SCA...PIGEON PT TO PT PINOS 10-60 NM SCA...PT PINOS TO PT PIEDRAS BLANCAS 10-60 NM SCA...PT PINOS TO PT PIEDRAS BLANCAS 0-10 NM SCA...MONTEREY BAY FROM 1 PM SCA...SF BAY NORTH OF THE BAY BRIDGE FROM 10 AM SCA...SF BAY SOUTH OF THE BAY BRIDGE FROM 10 AM && $$ PUBLIC FORECAST: SIMS AVIATION/MARINE: LARRY VISIT US AT WEATHER.GOV/SANFRANCISCO FOLLOW US ON FACEBOOK, TWITTER, AND YOUTUBE AT: WWW.FACEBOOK.COM/NWSBAYAREA WWW.TWITTER.COM/NWSBAYAREA WWW.YOUTUBE.COM/NWSBAYAREA  FXUS66 KMTR 091609 AFDMTR AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA 909 AM PDT MON MAR 9 2015 .SYNOPSIS...LOW CLOUDS AND PATCHY FOG CAN BE EXPECTED THIS MORNING FOR COMMUNITIES ALONG THE BAYS PLUS NEAR BAY VALLEYS. DRY AND MILD WEATHER CONDITIONS ARE EXPECTED TO STICK AROUND THROUGH TOMORROW. SHOWERS WILL BE A POSSIBILITY TUESDAY NIGHT THROUGH WEDNESDAY NIGHT AS A COLD FRONT MOVES THROUGH THE AREA. && .DISCUSSION...AS OF 09:15 AM PDT MONDAY... SATELLITE IMAGERY SHOWS COASTAL STRATUS BANKED ALONG MOST OF CALIFORNIAS COASTLINE THIS MORNING. FURTHERMORE... STRATUS HAS PUSHED ONSHORE INTO NEARLY ALL INLAND COASTAL VALLEYS FROM THE NORTH BAY THROUGH SALINAS VALLEY. GOES-W CLOUD THICKNESS IMAGERY AND COASTAL PROFILERS INDICATE THE STRATUS DECK IS AROUND 1000-1250FT THICK WITH BASES VARYING ON LOCATION BUT GENERALLY 200-800 FEET AGL. VISIBILITIES ARE EXPECTED TO IMPROVE VERY LATE THIS MORNING. A SIMILAR YET SHALLOWER STRATUS INTRUSION IS EXPECTED FOR TOMORROW MORNING. CURRENT FORECAST PACKAGE APPEARS ON TRACK PER THE TIMING OF THE STRATUS RETREAT... SO NO UPDATES PLANNED THIS MORNING. A LOW AMPLITUDE RIDGE WILL MAINTAIN SLIGHTLY ABOVE NORMAL TEMPERATURES FOR THE REGION TODAY AND AHEAD OF AN APPROACHING SYSTEM TOMORROW. THE APPROACHING STORM SYSTEM WILL RESULT IN INCREASING MID TO HIGH LEVEL CLOUD COVERAGE BEGINNING MIDDAY TOMORROW BEFORE INCREASING SIGNIFICANTLY TOMORROW NIGHT. THE FOCUS OF TODAYS FORECAST WILL BE ON THE TIMING...PROBABILITY...AND QUANTITY OF PRECIPITATION FROM THIS SYSTEM. WOULD LIKE TO SEE THE MODEL GUIDANCE CONVERGE ON A SINGLE SOLUTION WITH ONLY A COUPLE OF DAYS BEFORE THE SYSTEM ARRIVES. UNFORTUNATELY... FORECAST MODELS HAVE BEEN STUBBORN TO COMPROMISE. THE MODELS DO TEND TO AGREE ON THE TIMING OF THE ARRIVAL OF THE SYSTEM... 12Z WEDNESDAY. HOWEVER... THE CANADIAN AND EUROPEAN MODELS HAVE CONSISTENTLY BEEN WETTER THAN THE GFS BY A WIDE MARGIN AND IT IS ONLY IN THE MOST RECENT RUNS THAT THE GFS HAS BEEN TRENDING SLIGHTLY WETTER. THE LATEST FORECAST PACKAGE APPEARS TO FAVOR THE LOWER GFS VALUES AND THESE FALL IN LINE WITH SREF AND NAM OUTPUT. AT THIS TIME... IT APPEARS MOST POPULATED REGIONS WILL SEE LESS THAN A QUARTER OF AN INCH. A PROGRESSIVE AND RAPIDLY DEVELOPING RIDGE MOVES INTO THE VICINITY LATE WEDNESDAY INTO EARLY THURSDAY AND WILL BRING DRIER CONDITIONS AND ABOVE AVERAGE TEMPERATURES THROUGH THE REMAINDER OF THE WORKWEEK. A SECOND SYSTEM APPROACHING THE AREA IS DEFLECTED NORTHWARD BY THE REMNANTS OF THE RIDGE. WHAT HAPPENS NEXT IS LARGELY DEPENDENT ON THE STRENGTH AND POSITIONING OF THE RIDGE AS THE SECOND SYSTEM APPROACHES. A STRONGER RIDGE WOULD DEFLECT MOISTURE FURTHER NORTH WHEREAS A WEAKER RIDGE WOULD ALLOW MORE SOUTHWARD PROGRESSION OF THIS SYSTEM INTO OUR FORECAST AREA. && .PREV DISCUSSION...AS OF 3:15 AM PDT MONDAY...OVERNIGHT SATELLITE PRODUCTS SHOW WHAT ALMOST LOOKS LIKE A SUMMERTIME PATTERN WITH WIDESPREAD CLOUDS ALONG THE WATERS AND INTO ADJACENT VALLEYS. CLOUD HAVE EVEN STREAMED DOWN THE ENTIRE SANTA CLARA VALLEY AND SALINAS VALLEY. SURFACE GRADIENTS SHOW A MODERATE 2.2 MB ONSHORE/WESTERLY FLOW WITH AROUND 3 MB FROM THE NORTH. SYNOPTICALLY A RIDGE OF HIGH HIGH PRESSURE WILL REMAIN IN FIRM CONTROL OF OUR ENTIRE CWA TODAY WITH MOSTLY SUNNY CONDITIONS EXPECTED INLAND WHILE A MIX OF CLOUDS AND SUN WILL REMAIN AT THE COAST AS A SLIGHT ONSHORE PUSH WILL CONTINUE AT THE SURFACE. HIGHS WILL RANGE FROM 60S AT THE COAST TO 70S FOR MOST INLAND SPOTS. CLOUDS WILL BE ON THE INCREASE ON TUESDAY AS A COLD FRONT APPROACHES OUR AREA. THE BULK OF ENERGY AND MOISTURE WILL REMAIN WELL TO OUR NORTH....HOWEVER WITH 25-35 KT OF ISENTROPIC FLOW PLUS PW VALUES EXPECTED TO NEAR 1 INCH...WE SHOULD SEE AT LEAST SOME SHOWERS THROUGH OUR AREA FOR LATE TUESDAY INTO WEDNESDAY. POPS WERE PUSHED UP A BIT FOR ALL LOCATIONS AS ALL OF THE GLOBAL MODELS DUE BRING SOME MOISTURE TO OUR AREA. AMOUNTS WILL BE ON THE LIGHT SIDE WITH MOST URBAN SPOTS EXPECTED TO PICK UP LESS THAN A QUARTER OF AN INCH. ISOLATED GAUGES IN THE COASTAL RANGES COULD SEE AROUND HALF AN INCH. THE RIDGE WILL QUICKLY BUILD BACK TO THE REGION BY THURSDAY ALONG WITH A PRONOUNCED INCREASE IN 850 MB TEMPS. THIS WILL HELP TO PUSH TEMPS BACK TO WELL ABOVE NORMAL VALUES. HIGHS ON FRIDAY AND SATURDAY WILL LIKELY BE IN THE MID 60S TO 70S AT THE COAST WITH MID 70S TO MID 80S INLAND. A SECOND SYSTEM IS FORECAST TO MOVE TO THE PACNW/BC REGION OVER THE WEEKEND WITH THE FAR SOUTHERN EXTENT OF MOISTURE POSSIBLY BRUSHING ACROSS THE NORTHERN THIRD OF OUR CWA LATE SATURDAY INTO SUNDAY. NEWEST ECMWF CONTINUES TO KEEP ANY MOISTURE TO OUR NORTH WHILE THE GFS SHOWS A WEAK FRONT MOVING ACROSS OUR AREA WITH A FEW SHOWERS. LOOKING FURTHER DOWN THE ROAD...NO SIGNS OF A MAJOR STORM THROUGH AT LEAST THE MIDDLE OF NEXT WEEK. IN FACT...ECMWF BUILDS THE RIDGE SO STRONG THAT IT HAS THE ENTIRE WEST COAST OF THE CONUS AND BC COMPLETELY DRY BY THE MIDDLE OF NEXT WEEK. && .AVIATION...AS OF 4:45 AM PDT MONDAY...IFR/MVFR CIGS WILL PERSIST AT MOST TERMINALS THROUGH LATE MORNING...WITH FOG AT KSTS. THE MARINE LAYER REMAINS RELATIVELY SHALLOW AND SO CLEARING SHOULD OCCUR IN MOST AREAS BY 18Z. LIGHT AND VARIABLE WINDS WILL BECOME LIGHT ONSHORE IN THE AFTERNOON. VICINITY OF KSFO...IFR CIGS CLEARING BY 19Z. VFR THEREAFTER EXCEPT AREAS OF LOW CIGS BY LATE MONDAY NIGHT. LIGHT WEST WINDS INCREASING TO ABOUT 15 KNOTS BY LATE AFTERNOON AND CONTINUING THROUGH EARLY EVENING. CONFIDENCE MODERATE. KSFO BRIDGE APPROACH...SAME AS KSFO. MONTEREY BAY AREA TERMINALS...IFR CIGS THROUGH 18-19Z...VFR THROUGH EARLY EVENING WITH IFR CIGS LIKELY BY 03-04Z. WINDS LIGHT. CONFIDENCE MODERATE. && .MARINE...AS OF 08:25 AM PDT MONDAY...LIGHT TO MODERATE NORTHERLY WINDS WILL TURN TO LIGHT SOUTHERLY BY TUESDAY NIGHT AS A WEAK PACIFIC WEATHER SYSTEM APPROACHES THE WEST COAST. GENTLE SEAS WILL PREVAIL THROUGH THE FORECAST PERIOD. && .MTR WATCHES/WARNINGS/ADVISORIES... .TDAY...NONE. $$ PUBLIC FORECAST: DRP AVIATION/MARINE: DYKEMA VISIT US AT WEATHER.GOV/SANFRANCISCO FOLLOW US ON FACEBOOK, TWITTER, AND YOUTUBE AT: WWW.FACEBOOK.COM/NWSBAYAREA WWW.TWITTER.COM/NWSBAYAREA WWW.YOUTUBE.COM/NWSBAYAREA  FXUS66 KMTR 042159 AFDMTR AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA 259 PM PDT SAT APR 4 2015 .SYNOPSIS...A WEAK WEATHER SYSTEM WILL BRING SHOWERS TO THE CENTRAL COAST SUNDAY ESPECIALLY FROM THE SANTA CRUZ MOUNTAINS NORTHWARD. A STRONGER AND COLDER STORM SYSTEM WILL MOVE INTO CALIFORNIA MONDAY NIGHT AND TUESDAY DELIVERING WIDESPREAD AND HEAVIER RAINFALL. IN ADDITION...THERE IS A POTENTIAL FOR THUNDERSTORMS WITH SMALL HAIL ON TUESDAY AND TUESDAY EVENING AND SNOW IS FORECAST IN THE HILLS ABOVE 3500 FEET. DRY WEATHER WILL RETURN BY WEDNESDAY AFTERNOON AND CONTINUE THROUGH THE REST OF THE WEEK. && .DISCUSSION...AS OF 2:30 PM PDT SATURDAY...TEMPERATURES ARE MOSTLY IN THE 60S WITH THE MAIN WEATHER IMPACT BEING GUSTY WESTERLY WINDS THROUGH MUCH OF THE BAY AREA AND EAST BAY. HIGH CLOUDS ARE INCREASING AHEAD OF A SHORT WAVE TROF RIDING ALONG THE BASE OF THE COLD EASTERN PACIFIC TROF...AND IS POISED TO MOVE ONTO THE CENTRAL COAST LATE TONIGHT AND SUNDAY MORNING. MODELS CONSISTENT WITH TIMING WITH NEWER SOLUTIONS A LITTLE FURTHER SOUTH AS THE FEATURE MOVES ONSHORE. THIS SYSTEM IS WEAK DYNAMICALLY BUT DOES CONTAIN SUFFICIENT MOISTURE AND LIFT BELOW 600 MB TO PRODUCE SHOWERS. SATELLITE IMAGERY CONFIRMS A SOMEWHAT DISORGANIZED SYSTEM WITH HIGHER LEVEL MOISTURE WELL AHEAD OF LOWER LEVEL SUPPORT. ONSHORE FLOW AND ABUNDANT LOW LEVEL MOISTURE WITH SOME LIFT IS SUFFICIENT FOR HIGHER END POPS AND LOWER QPF AMOUNTS SUNDAY. RAINFALL SHOULD BEGIN ON THE SF PENINSULA EARLY SUNDAY MORNING AND SPREAD SOUTH AND EAST TO AROUND MONTEREY BAY BY EARLY AFTERNOON. LOOKS LIKE HEAVIEST RAINFALL PERHAPS A LITTLE OVER A QUARTER INCH WOULD OCCUR IN THE HILLS ALONG THE SAN MATEO COAST AND NORTH THROUGH MARIN COUNTY. MODELS EVEN INDICATE SOME SURFACE BASED CAPE UP TO 300 J/KG SUPPORTING CONVECTION...BUT DO NOT BELIEVE ENOUGH CLOUD DEPTH AND INDICATION OFFSHORE FROM SATELLITE IMAGERY TO INTRODUCE THUNDER INTO FORECAST. CLEARING IS EXPECTED SUNDAY NIGHT BEFORE STRONGER SYSTEM ARRIVES MONDAY NIGHT AND TUESDAY. PREVIOUS FORECAST PRETTY MUCH ON TRACK AND IN LINE WITH NEWER MODEL GUIDANCE. LOOK FOR SOUTH WINDS TO INCREASE AHEAD OF COLD FRONT BY MONDAY AFTERNOON AND CONTINUING INTO MONDAY NIGHT. GUSTS TO 50 MPH ARE POSSIBLE ALONG THE COASTLINE AND OVER HIGHER ELEVATIONS AHEAD OF FRONT. SNOW LEVELS WILL PLUMMET WITH THE COLD FRONT LATE MONDAY NIGHT AND TUESDAY MORNING AND SOME SNOWFALL ACCUMULATION IS POSSIBLE ABOVE 4000 FEET. MAIN MESSAGE WITH THIS STORM WILL BE FIRST SIGNIFICANT FRONTAL SYSTEM AND WIDESPREAD RAINFALL IN MANY WEEKS WITH BRIEF PERIOD OF MODERATE TO HEAVY RAIN POSSIBLE AS THE FRONT SWEEPS INLAND. TIMING FOR PRECIPITATION WOULD BE NORTH BAY MONDAY NIGHT AND INTO BAY AREA LATE MONDAY NIGHT AND EARLY TUESDAY. RAINFALL WILL SPREAD DOWN THE COAST AND EXIT THE AREA WITH SCATTERED SHOWERS BEHIND THE FRONT BY TUESDAY AFTERNOON. RAINFALL FROM MONDAY NIGHT AND TUESDAYS STORM SHOULD RANGE FROM NEARLY A HALF INCH IN VALLEYS UP TO 1.5 INCHES IN THE HIGHER ELEVATIONS. MODELS DIFFER ON PACE OF COLD LOW EXITING TO THE EAST BY WEDNESDAY. ECMWF...AND TO SOME EXTENT THE GEM...HAVE LOBE OF COLD ENERGY DROPPING SOUTH DOWN BACK SIDE OF TROF INTO CENTRAL COAST WEDNESDAY MORNING. THIS WOULD PROLONG SHOWERS ESPECIALLY MONTEREY COUNTY. GFS IS DRIER MUCH QUICKER WITH PLENTY OF SUNSHINE BY WEDNESDAY. OPTING FOR MIDDLE GROUND SOLUTION CLOSER TO GEM WITH SOME LINGERING SHOWERS INTO EARLY WEDNESDAY. DRY WEATHER IS EXPECTED WEDNESDAY AFTERNOON THROUGH THE END OF THE WEEK AS HIGH PRESSURE AND SPLIT FLOW RETURN. && .AVIATION...AS OF 10:45 AM PDT SATURDAY...VFR TODAY. GUSTY ONSHORE WINDS THIS AFTERNOON AS THE SFO-SAC GRADIENT REACHES NEARLY 4 MB. LIGHT SCATTERED RAIN SHOWERS BEGIN TOMORROW MORNING ACROSS THE AREA FROM SJC NORTH AND LAST THROUGH AROUND MID DAY. VICINITY OF KSFO...VFR. WESTERLY WIND GUSTS UP TO AROUND 27 KT THIS AFTERNOON AS THE ONSHORE GRADIENT INCREASES. SFO BRIDGE APPROACH...SIMILAR TO KSFO. MONTEREY BAY AREA TERMINALS...VFR. GUSTY WINDS AT SNS THIS AFTERNOON. && .MARINE...AS OF 3:43 AM PDT SATURDAY...NORTHWESTERLY WINDS WILL GRADUALLY DECREASE OVER THE COASTAL WATERS THROUGH TODAY...BUT ONSHORE WINDS WILL INCREASE OVER THE SAN FRANCISCO BAY AND MONTEREY BAY BY AFTERNOON. A FEW SHOWERS ARE POSSIBLE WELL AFTER MIDNIGHT TONIGHT INTO SUNDAY AS A WEAK COOL FRONT MOVES EAST OVER THE COASTAL WATERS. A DEEPENING LOW PRESSURE SYSTEM FROM THE GULF OF ALASKA WILL REACH THE NORTHERNMOST CALIFORNIA COAST MONDAY AFTERNOON AND SWING A COLD FRONT SOUTHEASTWARD ACROSS THE COASTAL WATERS AND BAY AREA LATE MONDAY NIGHT INTO TUESDAY MORNING. DRY WEATHER WILL RETURN MID WEEK. WEAK HIGH PRESSURE IS EXPECTED MID TO LATE WEEK. && .MTR WATCHES/WARNINGS/ADVISORIES... .TNGT...SCA...SF BAY NORTH OF THE BAY BRIDGE UNTIL 9 PM SCA...MONTEREY BAY UNTIL 9 PM SCA...PT ARENA TO PT REYES 0-10 NM UNTIL 9 PM SCA...PT REYES TO PIGEON PT 0-10 NM UNTIL 9 PM SCA...PIGEON PT TO PT PINOS 0-10 NM UNTIL 9 PM SCA...PIGEON PT TO PT PINOS 10-60 NM UNTIL 9 PM SCA...PT ARENA TO PT REYES 10-60 NM UNTIL 3 PM SCA...PT REYES TO PIGEON PT 10-60 NM UNTIL 3 PM SCA...PT PINOS TO PT PIEDRAS BLANCAS 0-10 NM SCA...PT PINOS TO PT PIEDRAS BLANCAS 10-60 NM UNTIL 3 AM && $$ PUBLIC FORECAST: KBB AVIATION: AC MARINE: CANEPA VISIT US AT WEATHER.GOV/SANFRANCISCO FOLLOW US ON FACEBOOK, TWITTER, AND YOUTUBE AT: WWW.FACEBOOK.COM/NWSBAYAREA WWW.TWITTER.COM/NWSBAYAREA WWW.YOUTUBE.COM/NWSBAYAREA  FXUS66 KMTR 031555 AFDMTR AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA 855 AM PDT SUN MAY 3 2015 .SYNOPSIS...A RELATIVELY DEEP MARINE LAYER AND PERSISTENT ONSHORE FLOW WILL MAINTAIN AREAS OF NIGHT AND MORNING LOW CLOUDS THROUGH THE MIDDLE OF THE WEEK...ALONG WITH TEMPERATURES NEAR TO SLIGHTLY BELOW NORMAL. AN UPPER LEVEL LOW IS THEN FORECAST TO DEVELOP OVER CALIFORNIA BY THURSDAY. THIS LOW WILL MIX OUT THE MARINE LAYER...BUT ALSO MAINTAIN RELATIVELY COOL WEATHER CONDITIONS INTO THE SECOND HALF OF THE WEEK. THERE IS ALSO A SLIGHT CHANCE OF SHOWERS WITH THIS WEATHER SYSTEM...MAINLY ACROSS THE SOUTHERN PORTION OF OUR AREA FROM LATE THURSDAY NIGHT THROUGH FRIDAY. && .DISCUSSION...AS OF 08:41 AM PDT SUNDAY...DEEP MARINE LAYER THIS MORNING IS SLIGHTLY OVER 2000 FEET AT FORD ORD. LAST NIGHTS MODIS AND EARLY MORNING GOES IMAGERY SHOWS CLOUD THICKNESS AROUND 1000 FEET...DEEPER SOUTH OF THE BAY AREA AND SHALLOWER NORTH BAY. IMPLICATION IS FOR EARLIER DISSIPATION NORTH BAY AND INLAND...BUT STRENGTH OF ONSHORE FLOW SHOULD KEEP COASTAL AREAS IN THE STRATUS MUCH OF THE DAY. CURRENT FORECAST LOOKS ON TRACK WITH MORNING TEMPERATURES IN THE 50S CLIMBING TO THE 60S ALONG THE COAST TO 70S INLAND THIS AFTERNOON. ONSHORE FLOW TO CONTINUE NEXT FEW DAYS WITH EXTENSIVE PUSH OF STRATUS INLAND NIGHTS AND MORNINGS. LATEST NAM STRENGTHENS ONSHORE GRADIENT TO 3.7 MB SFO TO SAC MONDAY AFTERNOON. MONDAY MAY ACTUALLY BE THE COOLEST DAY OF THE NEXT SEVERAL...THEN MARINE LAYER MIXING INCREASES TOWARD MIDWEEK WITH UPPER LEVEL TROFING DEVELOPING ALONG THE COAST AND COASTAL TEMPERATURES MAY WARM SLIGHTLY. && .PREV DISCUSSION...AS OF 3:10 AM PDT SUNDAY...THE COOLING TREND THAT BEGAN ON FRIDAY WILL CONTINUE TODAY...ALTHOUGH THE MAGNITUDE OF TODAY'S COOLING IS EXPECTED TO BE LESS THAN WHAT OCCURRED DURING THE PAST TWO DAYS. A WEAK UPPER TROUGH CURRENTLY OFF THE WEST COAST IS FORECAST TO SHIFT EASTWARD OVER THE CA COAST BY MONDAY MORNING. BOTH THE NAM AND WRF MODELS INDICATE THIS WILL RESULT IN AN EVEN GREATER INLAND SURGE OF MARINE LAYER CLOUDS TONIGHT...AS WELL AS CONTINUED COOL CONDITIONS INTO MONDAY. AFTER THE WEAK UPPER TROUGH MOVES INLAND ON MONDAY...SURFACE HIGH PRESSURE WILL STRENGTHEN OFF THE NORTHERN CA COAST...RESULTING IN INCREASING NORTHWEST WINDS ALONG THE COAST ON MONDAY NIGHT AND TUESDAY. THESE WINDS SHOULD PRODUCE SUFFICIENT MIXING TO CLEAR OUT MUCH OF THE LOW CLOUDINESS BY TUESDAY AFTERNOON AND THUS BRING ABOUT SLIGHT WARMING ON TUESDAY. AN UPPER LOW IS FORECAST TO DEVELOP OVER THE PAC NW BY MIDWEEK. THE GFS AND ECMWF AGREE REASONABLY WELL IN DROPPING THAT LOW DUE SOUTH ACROSS NORTHERN AND CENTRAL CALIFORNIA FROM LATE WEDNESDAY NIGHT THROUGH THURSDAY NIGHT...AND THEN EJECTING THAT LOW EASTWARD ON FRIDAY. BOTH MODELS ALSO FORECAST SCATTERED LIGHT PRECIPITATION ACROSS PORTIONS OF OUR AREA FROM THURSDAY AFTERNOON THROUGH LATE FRIDAY...WITH THE MOST WIDESPREAD SHOWER ACTIVITY PROJECTED TO OCCUR ACROSS THE SOUTHERN PART OF OUR AREA LATE THURSDAY NIGHT AND FRIDAY MORNING AS SHORTWAVE ROTATES INLAND OVER THE CENTRAL COAST. THE AIRMASS OVER OUR AREA WILL COOL SEVERAL DEGREES FROM LATE WEDNESDAY INTO THURSDAY AS THE UPPER LOW DROPS IN FROM THE NORTH. THIS COOLING WILL BE SUFFICIENT TO MIX OUT THE MARINE LAYER ACROSS THE NORTHERN PART OF OUR AREA BY LATE WEDNESDAY AND IN ALL AREAS BY THURSDAY. TEMPERATURES WILL COOL BELOW NORMAL IN ALL AREAS BY THURSDAY AND REMAIN COOL THROUGH THE END OF THE WEEK. THE UPPER LOW IS FORECAST TO MOVE WELL OFF TO OUR EAST BY LATE FRIDAY...AND SHORTWAVE RIDGING IS EXPECTED TO PRODUCE DRY AND SLIGHTLY WARMER WEATHER NEXT WEEKEND. BUT THE LONGER RANGE MODELS MAINTAIN AN UNSETTLED PATTERN...WITH ANOTHER WEAK WEATHER SYSTEM PROJECTED TO APPROACH CALIFORNIA EARLY NEXT WEEK. && .AVIATION...AS OF 4:36 AM PDT SUNDAY...AS NOTED ABOVE DEEP MARINE LAYER IN PLACE WITH WIDESPREAD MVFR CIGS WITH A FEW POCKETS OF IFR CONDITIONS. KSJC AND KLVK ARE ON THE EDGE AND LATEST TRENDS SUGGEST STRATUS AROUND SUNRISE. BASED ON LATEST GUIDANCE CLEARING WILL BE MID MORNING FOR MANY LOCATIONS WITH VFR THIS AFTERNOON. CIGS RETURN AGAIN TONIGHT. CONF IS MEDIUM-HIGH. VICINITY OF KSFO...MVFR CIGS WITH CLEARING 17-18Z. BRIEF PERIOD OF NE WINDS POSSIBLE. STRONGER WEST PUSH OF WINDS THIS AFTERNOON. SFO BRIDGE APPROACH...SIMILAR TO SFO. MONTEREY BAY AREA TERMINALS...MVFR CIGS THROUGH 18Z. VFR THIS AFTERNOON. && .BEACHES...AS OF 4:36 AM PDT SUNDAY...NO REAL CHANGE FROM PREVIOUS FORECAST. A SERIES OF LONG PERIOD SOUTHERLY SWELLS WILL IMPACT THE CENTRAL COAST TODAY. PT CONCEPTION BUOY IS ALREADY SHOWING 3.5 FT AT 25 SECONDS. ALTHOUGH THE WAVE HEIGHTS ASSOCIATED WITH THESE LONG PERIOD WAVES WILL BE RELATIVELY SMALL...4 TO 6 FEET...THE POWERFUL NATURE OF LONG PERIOD WAVES WILL RESULT IN EXCEPTIONALLY STRONG RIP CURRENTS ALONG THE COAST ESPECIALLY ON SOUTHERLY FACING BEACHES SUCH AS STINSON BEACH IN MARIN COUNTY AND THE BEACHES ALONG THE MONTEREY BAY COAST OF SANTA CRUZ COUNTY. ADDITIONALLY...THESE LONG PERIOD WAVES WILL ALSO RESULT IN LARGE SHORE BREAK AT TWIN LAKES STATE BEACH AND THE SANTA CRUZ BOARDWALK BEACH. LARGE SHORE BREAK CAN RESULT IN NECK AND BACK INJURIES. IF YOU PLAN ON ENTERING THE WATER PLEASE DO SO NEAR A LIFEGUARD AND ALWAYS KEEP AN EYE ON THE OCEAN WHEN VISITING THE BEACH. && .MARINE...AS OF 04:31 AM PDT SUNDAY...GUSTY NORTHERLY WINDS WILL CONTINUE OVER THE NORTHERN OUTER WATERS THROUGH EARLY NEXT WEEK. ELSEWHERE...SOUTHERLY FLOW WILL CONTINUE TODAY. NORTHERLY FLOW WILL DEVELOP OVER MOST OF THE COASTAL WATERS TONIGHT AND MONDAY AS HIGH PRESSURE BUILDS OVER THE REGION. A LONG PERIOD SOUTHERLY SWELL WILL IMPACT THE COASTAL WATERS SUNDAY AND CONTINUE THROUGH TUESDAY. && .MTR WATCHES/WARNINGS/ADVISORIES... .TDAY...SCA...PT ARENA TO PT REYES 10-60 NM SCA...SF BAY NORTH OF THE BAY BRIDGE FROM 3 PM && $$ PUBLIC FORECAST: KBB AVIATION/MARINE: MM VISIT US AT WEATHER.GOV/SANFRANCISCO FOLLOW US ON FACEBOOK, TWITTER, AND YOUTUBE AT: WWW.FACEBOOK.COM/NWSBAYAREA WWW.TWITTER.COM/NWSBAYAREA WWW.YOUTUBE.COM/NWSBAYAREA  FXUS66 KMTR 101902 CCA AFDMTR AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA 1153 AM PDT SUN MAY 10 2015 .SYNOPSIS...A RELATIVELY DEEP MARINE LAYER ALONG WITH MODERATE ONSHORE FLOW WILL CONTINUE TO RESULT IN RELATIVELY COOL CONDITIONS ALONG WITH WIDESPREAD NIGHT AND MORNING LOW CLOUDS THROUGH MONDAY. AN UPPER LEVEL TROUGH WILL DEVELOP NEAR THE WEST COAST EARLY THIS WEEK AND THEN PERSIST THROUGH THE END OF THE WEEK. THIS TROUGH WILL MAINTAIN COOLER THAN NORMAL TEMPERATURES THROUGH THE WEEK AND PRODUCE A SLIGHT CHANCE OF SHOWERS DURING THE SECOND HALF OF THE WEEK. && .DISCUSSION...AS OF 9:12 AM PDT SUNDAY...ITS A CLOUDY START TO MOTHERS DAY FOR MOST VALLEY AND COASTAL LOCATIONS WITH A 2000 FOOT MARINE LAYER IN PLACE. TEMPS ABOVE THE MARINE LAYER ARE ALREADY ABOUT 60 DEGREES SO INLAND AREAS WILL WARM INTO THE LOWER 70S AS THE MARINE LAYER BURNS OFF. COASTAL AREAS WILL STAY CLOUDY ALL DAY WITH TEMPERATURES GENERALLY IN THE 60S INSIDE SF BAY TODAY. THE NEXT TROUGH IS ALREADY APPROACHING THE OREGON COAST AND WILL KEEP ONSHORE FLOW IN PLACE TONIGHT INTO MONDAY. THIS WILL LEAD TO SOME COASTAL DRIZZLE AS THE MARINE LAYER DEEPENS WITH BLUSTERY WINDS NEAR THE COAST AND BAYS MONDAY AS THE UNSEASONABLY COOL UPPER LOW DROPS INTO NORTHERN CALIFORNIA. FOR MONDAY EXPECT ONLY UPPER 50S AT THE BEACHES WITH 60S THE REST OF THE DISTRICT AND VERY FEW READINGS INTO THE 70S WITH THE ONSHORE FLOW AND COLD UPPER LOW OVER THE STATE. COOL PATTERN WILL STAY IN PLACE THIS WEEK WITH A TROUGH ALONG THE WEST COAST. BY THURSDAY THE NEXT UPPER LOW WILL APPROACH THE COAST BUT LATEST TRENDS KEEP THE MAIN RAIN ASSOCIATED WITH THIS LOW OFFSHORE. WILL LOOK OVER FULL 12Z SUITE AND MAKE ADJUSTMENTS WITH THE AFTERNOON PACKAGES. MAIN THEME LOOKS TO BE CONTINUED BELOW NORMAL TEMPERATURES WITH NO HOT WEATHER IN SITE. RAIN CHANCES LOOK SLIM BUT SOME SHOWERS BY LATE IN THE WEEK REMAINS POSSIBLE SO SLIGHT CHANCES WILL STAY IN THE FORECAST. 10-15 DAY MODEL RUNS KEEP WEST COAST TROUGH IN PLACE WITH BELOW NORMAL TEMPERATURES. && .PREV DISCUSSION...AS OF 3:40 AM PDT SUNDAY...A WEAK SHORTWAVE RIDGE HAS DEVELOPED OVER CALIFORNIA....RESULTING IN A DECREASE IN THE DEPTH OF THE MARINE LAYER OF NEARLY 1000 FEET SINCE YESTERDAY MORNING. BUT THE MARINE LAYER REMAINS RELATIVELY DEEP AT 2000 FEET. IN ADDITION...ONSHORE FLOW HAS STRENGTHENED SLIGHTLY SINCE YESTERDAY MORNING. THE RESULT HAS BEEN WIDESPREAD LOW CLOUD DEVELOPMENT ACROSS INLAND AREAS EARLY THIS MORNING. EXPECT SLOW CLEARING TODAY AND CONTINUED COOLER THAN NORMAL WEATHER CONDITIONS. HOWEVER...THE REDUCTION IN THE DEPTH OF THE MARINE LAYER UNDER THE WEAK RIDGE SHOULD RESULT IN SLIGHTLY EARLIER CLEARING FOR INLAND AREAS...AS WELL AS A FEW DEGREES OF WARMING INLAND. COASTAL AREAS ARE NOT EXPECTED TO SEE MUCH CHANGE AND SOME OCEAN BEACHES WILL LIKELY REMAIN UNDER THE "MAY GRAY" THROUGH THE AFTERNOON HOURS...MUCH LIKE YESTERDAY. WATER VAPOR SATELLITE IMAGERY SHOWS AN UPPER TROUGH APPROACHING THE PAC NW AND FAR NORTHERN CA AT THE PRESENT TIME. AN UPPER LOW IS FORECAST TO DEVELOP IN THIS TROUGH OFF THE COAST OF OREGON LATER TODAY....AND THE MODELS AGREE THAT THIS LOW WILL THEN DROP SE TO THE CA/OR BORDER BY TONIGHT. ALL CONVECTIVE PRECIP ASSOCIATED WITH THIS UPPER LOW IS FORECAST TO REMAIN WELL TO OUR NORTH. HOWEVER...AS THE LOW DROPS SOUTHEAST IT SHOULD TRIGGER AN INCREASE IN THE DEPTH OF THE MARINE LAYER AS WELL AS AN INCREASE IN ONSHORE FLOW OVERNIGHT AND INTO MONDAY MORNING. PATCHY DRIZZLE HAS BEEN ADDED TO THE FORECAST FOR COASTAL AREAS LATE TONIGHT AND INTO MONDAY MORNING. THE COMBINATION OF A COOLER AIRMASS ALOFT AND STRONGER LOW LEVEL WINDS SHOULD HELP MIX OUT THE MARINE LAYER TO SOME EXTENT BY MONDAY AFTERNOON AND EVEN MORE SO BY TUESDAY. SO IT'S LIKELY WE WILL GRADUALLY SEE MORE AFTERNOON SUN IN COASTAL AREAS OVER THE NEXT FEW DAYS. BUT TEMPERATURES ARE EXPECTED TO REMAIN BELOW SEASONAL NORMS REGION-WIDE THROUGHOUT THE WEEK. A SECOND UPPER LOW IS FORECAST TO DROP SOUTH OFFSHORE ON WEDNESDAY AND THURSDAY AND THEN SWING INLAND ACROSS SOUTHERN CALIFORNIA ON FRIDAY. THE MODELS AGREE THAT PRECIP WITH THIS SYSTEM WILL MOSTLY REMAIN OFFSHORE THROUGH WEDNESDAY...AND POSSIBLY THROUGH MOST OF THURSDAY AS WELL. IT'S DIFFICULT TO PINPOINT WHEN AND WHERE THE BEST CHANCE OF MEASURABLE RAIN WILL OCCUR GIVEN THAT THE MODELS PREDICT SCATTERED LIGHT QPF ACROSS MUCH OF CALIFORNIA LATER THIS WEEK. SO HAVE GONE AHEAD AND BLANKETED MOST OF OUR CWA WITH CHANCE/SLIGHT CHANCE POPS FROM THURSDAY THROUGH SATURDAY...WITH THE HIGHEST CHANCES ACROSS THE SOUTHERN PART OF OUR AREA ON THURSDAY NIGHT AND FRIDAY WHEN THE LOW TRACKS INLAND TO OUR SOUTH. RAINFALL TOTALS WITH THIS SYSTEM ARE EXPECTED TO BE LESS THAN A QUARTER OF AN INCH IN MOST AREAS. UNSETTLED AND COOL CONDITIONS ARE EXPECTED TO PERSIST THROUGH NEXT WEEKEND AS YET ANOTHER WEAK UPPER LOW IS FORECAST TO DEVELOP OFF THE NORTHERN CA COAST BY LATE SUNDAY. && .AVIATION...AS OF 11:45 AM PDT SUNDAY... A SHALLOWER MARINE LAYER AT PLAY TODAY VERSUS YESTERDAY IS CONTRIBUTING TO AN EARLIER BURN OFF/MIX OUT VERSUS PERSISTENCE THIS MORNING. AN APPROACHING FRONTAL BOUNDARY IS HELPING TO CLEAR AWAY THE COASTAL STRATUS FROM NORTH TO SOUTH. GOES-W CLOUD THICKNESS PRODUCT SHOWING AVERAGE THICKNESS AROUND 500 FT OVER MOST LOCATIONS AND A 1000 FT LAYER ALONG THE PACIFIC SHORELINE OF THE SF PENINSULA. WEAK ONSHORE GRADIENT IS ENOUGH TO ALLOW FUNNELING OF MARINE AIRMASS THROUGH THE SAN BRUNO GAP AND IS LEADING TO A STALLED MIX OUT AS THE AIR MASSES PLAY TUG OF WAR OVER KSFO. FEW/SCT CLOUDS WILL LIKELY LINGER INTO THE EARLY AFTERNOON AOA 1500 FT BEFORE CLEARING OUT LATER TODAY. MVFR/IFR CIGS WILL RETURN TONIGHT AROUND AN HOUR OR TWO LATER THAN LAST NIGHT. VICINITY OF KSFO... EDGE OF STRATUS DECK DIRECTLY OVER TERMINAL WITH APPROACH CLEAR. MAY SEE STRATUS IN A HOLDING PATTERN NEAR TERMINAL UNTIL COASTAL STRATUS CLEARS FROM THE NORTH AND CUTS OFF MARINE LAYER FEED THROUGH SAN BRUNO GAP. VFR CIGS THIS AFTERNOON WITH RETURN OF MVFR CIGS 03-04Z. IFR CIGS POSBL BY 10Z. LIGHT TO MODERATE SEA BREEZE THIS AFTERNOON. KSFO BRIDGE APPROACH... APPROACH MOSTLY CLEAR. MONTEREY BAY AREA TERMINALS...EDGE OF STRATUS DECK SCATTERING OUT OVER THE TERMINAL. POSBL SCT010/BKN010 DECK IN VICINITY OF TERMINAL THROUGH 20Z THEN VFR CIGS. MVFR CIGS RETURNS AOA 02Z. IFR OVERNIGHT. ONSHORE FLOW 12KT OR LESS THIS AFTERNOON. && .MARINE...AS OF 11:29 AM PDT SUNDAY...NORTHWEST WINDS WILL STRENGTHEN TODAY AND PERSIST EARLY INTO THE WEEK. NORTHWEST SWELL BUILDS TONIGHT THROUGH THE NEXT FEW DAYS. WIND AND SEAS TAPER OFF MIDWEEK. && .MTR WATCHES/WARNINGS/ADVISORIES... .TDAY...SCA...PT ARENA TO PT REYES 0-10 NM SCA...PT ARENA TO PT REYES 10-60 NM SCA...PT PINOS TO PT PIEDRAS BLANCAS 0-10 NM FROM 3 PM SCA...PT REYES TO PIGEON PT 10-60 NM FROM 3 PM && $$ PUBLIC FORECAST: RWW AVIATION/MARINE: DRP VISIT US AT WEATHER.GOV/SANFRANCISCO FOLLOW US ON FACEBOOK, TWITTER, AND YOUTUBE AT: WWW.FACEBOOK.COM/NWSBAYAREA WWW.TWITTER.COM/NWSBAYAREA WWW.YOUTUBE.COM/NWSBAYAREA  FXUS66 KMTR 191758 AFDMTR AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA 1058 AM PDT TUE MAY 19 2015 .SYNOPSIS...UNSEASONABLY COOL WEATHER IS EXPECTED TO PREVAIL THROUGH THE FORECAST PERIOD. LINGERING INSTABILITY WILL PROMOTE ISOLATED SHOWERS TODAY OVER THE NORTH BAY HILLS. A LOW PRESSURE SYSTEM WILL SLIDE INTO CENTRAL CALIFORNIA THURSDAY RESULTING IN MORE WIDESPREAD SHOWER ACTIVITY. THE WEATHER IS EXPECTED TO DRY OUT FOR THE WEEKEND WITH MORE SEASONABLE TEMPERATURES RETURNING. && .DISCUSSION...AS OF 8:55 AM PDT TUESDAY...MORE THAN A DOZEN REPORTS THIS MORNING OF DRIZZLE/LIGHT RAIN THIS MORNING. THIS PROMPTED A SMALL FORECAST UPDATE TODAY TO ADD A SLIGHT CHANCE FOR SHOWERS AT LEAST UNTIL NOON. CLOUDS WILL BE SLOW TO BURN-OFF TODAY WITH THE BEST CHANCE TO SEE SUNSHINE FOR INLAND SPOTS. COASTAL SPOTS WILL GENERALLY STAY CLOUDY ALTHOUGH SHOULD SEE A FEW BREAKS FOR THOSE SPOTS DURING THE AFTERNOON. HIGHS WILL MOSTLY BE IN THE 60S AT THE COAST WITH MID 60S TO LOWER 70S INLAND. CURRENT SUITE OF MODELS SHOWS AT LEAST A CHANCE OF SHOWERS OVER THE NEXT SEVERAL DAYS WHICH SEEMS REASONABLE IN LIGHT OF THE OVERALL SYNOPTIC PATTERN PLUS INSTABILITY. WILL BE INCREASING A POPS A BIT FOR THE AFTERNOON PACKAGE. .PREVIOUS DISCUSSION...THE CURRENT IR SATELLITE FOG PRODUCT IS SHOWING LOW CLOUDS PRESENT AROUND MUCH OF THE FORECAST AREA THIS MORNING. THE SAN JOSE STATE AND THE SAN FRANCISCO EXPLORATORIUM RADIOMETERS ARE BOTH INDICATING A SUBTLE INVERSION AT APPROXIMATELY 3000 FEET WITH A LOW CLOUD LAYER PRESENT. THE CURRENT SATELLITE WATER VAPOR IMAGE IS SHOWING A BROAD AREA OF LOW PRESSURE POSITIONED OVER THE WESTERN CONUS...WITH A LOW PRESSURE SYSTEM POSITIONED ALONG THE ALEUTIANS AND A SECONDS LOW PRESSURE SYSTEM MOVING THROUGH THE GULF OF ALASKA. THE 0000Z ECMWF AND 0600Z GFS40 HAVE INITIALIZED WELL WITH THE CURRENT SYNOPTIC WEATHER PATTERN AND REMAIN IN GOOD AGREEMENT THROUGH THE WEEKEND. BOTH MODELS RETAIN A GENERALLY TROUGHY PATTERN OVER THE WESTERN CONUS THROUGH REMAINDER OF THE WORK WEEK...PROMOTING BELOW NORMAL TEMPERATURES FOR MUCH OF THE FORECAST AREA. BOTH MODELS ALSO SLIDE THE LOW PRESSURE SYSTEM CURRENTLY POSITIONED IN THE GULF OF ALASKA SOUTH INTO NORTHERN AND CENTRAL CALIFORNIA BY THURSDAY. THIS LOW PRESSURE SYSTEM WILL PROMOTE A POSSIBILITY OF SHOWERS ON THURSDAY AND FRIDAY BUT LACKS THE INSTABILITY NEEDED TO SUPPORT THUNDERSTORMS. THIS LOW PRESSURE SYSTEM QUICKLY SLIDES EAST WITH A RIDGE OF HIGH PRESSURE BUILD IN OVER THE EASTERN PACIFIC AND CALIFORNIA COAST. THE BUILDING RIDGE WILL HELP TO PROVIDE MORE SEASONABLE WEATHER TO OUR AREA. THE CLIMATE PREDICTION CENTER'S 6 TO 10 DAY OUTLOOK IS FOR NORMAL TEMPERATURES AND PRECIPITATION. THE 8 TO 14 DAY OUTLOOK IS SUGGESTING A POSSIBILITY OF ABOVE NORMAL TEMPERATURES WITH NEAR NORMAL PRECIPITATION. && .AVIATION...AS OF 11:00 AM PDT TUESDAY... ROBUST STRATUS DECK OVER MOST OF THE MONTEREY AND SF BAY AREA LATE THIS MORNING. GOES-W CLOUD THICKNESS PRODUCT AND PILOT REPORT REPORT CLOUD LAYER REPORT 1500-2500FT CLOUD DEPTH WITH BASES DOWN TO AROUND 1500 FEET. CIG BASES GRADUALLY LIFT THROUGH THE DAY BUT MVFR STILL LIKELY FOR MOST LOCATIONS THROUGH THE TAF PERIOD. BRIEF SCT/VFR POSBL LATE AFTERNOON/EARLY EVENING BEFORE MVFR CIGS RETURN FOR THE EVENING/OVERNIGHT PERIOD. PERSISTENT LIGHT TO MODERATE ONSHORE WINDS. VICINITY OF KSFO... MVFR CIGS THROUGH MOST OF THE DAY WITH BRIEF SCT/VFR POSBL 23Z-03Z PRIOR TO RETURN OF MVFR CIGS AFTER 03Z. LIGHT TO MODERATE ONSHORE FLOW THROUGH THE FORECAST PERIOD. KSFO BRIDGE APPROACH...SIMILAR TO KSFO. MONTEREY BAY AREA TERMINALS... MVFR CIGS WITH LIFTING CLOUD BASES AND INCREASING LIKELIHOOD OF SCATTERING OUT/VFR CIGS AFTER 21-23Z. MVFR CIGS RETURN NO LATER THAN 03-04Z THU. LIGHT TO MODERATE ONSHORE FLOW THROUGH THE FORECAST PERIOD. && .MARINE...AS OF 10:47 AM PDT TUESDAY...LIGHT TO MODERATE NORTHWEST WINDS OVER THE COASTAL WATERS THROUGH MIDWEEK. STRONGER COASTAL WINDS WILL BE PRESENT ALONG THE SONOMA COAST... BETWEEN THE GOLDEN GATE AND ANGEL ISLAND... ALONG SANTA CRUZ COUNTY INTO NORTHERN MONTEREY BAY... AND ALONG THE BIG SUR COASTLINE THIS AFTERNOON. NORTHWEST WINDS WILL INCREASE OVER THE COASTAL WATERS LATE IN THE WEEK. && .MTR WATCHES/WARNINGS/ADVISORIES... .TDAY...SCA...MONTEREY BAY FROM 3 PM SCA...PT ARENA TO PT REYES 0-10 NM FROM 3 PM SCA...PIGEON PT TO PT PINOS 0-10 NM FROM 3 PM SCA...PT PINOS TO PT PIEDRAS BLANCAS 0-10 NM FROM 3 PM SCA...SF BAY NORTH OF THE BAY BRIDGE FROM 1 PM SCA...SF BAY SOUTH OF THE BAY BRIDGE FROM 1 PM && $$ PUBLIC FORECAST: BELL/LARRY AVIATION/MARINE: DRP VISIT US AT WEATHER.GOV/SANFRANCISCO FOLLOW US ON FACEBOOK, TWITTER, AND YOUTUBE AT: WWW.FACEBOOK.COM/NWSBAYAREA WWW.TWITTER.COM/NWSBAYAREA WWW.YOUTUBE.COM/NWSBAYAREA  FXUS66 KMTR 301153 AFDMTR AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA 453 AM PDT SAT MAY 30 2015 .SYNOPSIS...SEASONABLE WEATHER TODAY WITH TEMPERATURES 60S COAST...70S AROUND THE BAY AND SOME 80S WELL INLAND. AS THE MARINE LAYER BURNS OFF TODAY HIGH CLOUDS WILL BE ON THE INCREASE AHEAD OF AN INCOMING WEATHER SYSTEM. SLIGHT COOLING TREND ON SUNDAY AS THE SYSTEM STAYS OFF THE COAST AND BRINGS ONLY A SLIGHT CHANCE OF SHOWERS TO THE FAR NORTH BAY. ZONAL FLOW MONDAY THROUGH MOST OF NEXT WEEK WILL KEEP TEMPERATURES ON THE COOL SIDE OF NORMAL WITH DRY WEATHER AND WIDESPREAD NIGHT AND MORNING STRATUS. && .DISCUSSION...AS OF 3:21 AM PDT SATURDAY...THE MARINE LAYER IS COMPRESSING WITH THE FORT ORD PROFILER AT AROUND 1000 FEET. DENSE FOG OF 1/4 MILE OR LESS IS NOW BEING REPORTED AT WATSONVILLE AND MONTEREY AND FURTHER EVIDENCE OF THE COMPRESSED LAYER. GIVEN THE SHALLOW NATURE OF THE MARINE LAYER IT SHOULD MIX OUT FAIRLY QUICKLY AROUND THE BAY. HOWEVER THERE ARE SOME INCREASING MID AND HIGH CLOUDS ASSOCIATED WITH AN UPPER TROUGH OUT NEAR 35N/140W THAT MAY INHIBIT BURN OFF CLOSER TO THE COAST. THE INLAND VALLEYS SHOULD BE ABLE TO WARM INTO THE 80S BUT 60S AND 70S WILL CONTINUE TO BE THE RULE COAST AND BAYS. INCOMING UPPER LOW IS FAIRLY ROBUST ON SUNDAY BUT MAIN RAIN SHIELD WILL STAY OFF SHORE AND THEN SHIFT NORTH TOWARDS CAPE MENDOCINO AS IT WEAKENS. CANT COMPLETELY RULE OUT A STRAY NORTH BAY SHOWER BUT MAIN IMPACT WILL BE SOME INCREASING CLOUDS...DEEPER MARINE LAYER AND COOLER INLAND TEMPS FOR SUNDAY AFTERNOON. THE BAY AREA WILL STAY IN THE WARM CORE OF THE SURFACE FRONT AND LOW SO NO SIGNIFICANT SYNOPTIC COOLING BUT A ROBUST SEABREEZE SUNDAY AFTERNOON WILL USHER COOLER MARINE AIR INTO THE DELTA AND FAR EAST BAY BY SUNDAY EVENING. WILL BE FOLLOWING THE ECMWF SOLUTION FOR THE MID AND LONG RANGE WHICH KEEPS THE FLOW ZONAL EARLY IN THE WEEK AND THEN SHOWS UPPER TROUGHING MID TO LATE WEEK. THIS WILL KEEP TEMPERATURES NEAR OR SLIGHTLY BELOW NORMAL FOR THE FIRST WEEK OF JUNE...SIMILAR TO WHAT WE SAW MUCH OF MAY. OTHER THAN COASTAL DRIZZLE THE FORECAST REMAINS DRY IN THE LONG RANGE. && .AVIATION...AS OF 4:45 AM PDT SATURDAY... HIGH PRESSURE WITH SIGNIFICANT SUBSIDENCE ALOFT IS RESULTING IN A COMPRESSED MARINE LAYER AND WIDESPREAD IFR CIGS THIS MORNING. CLOUD BASES ARE RANGING FROM THE SURFACE TO 1000 FT WITH FOG BEING REPORTED AT KMRY. THE CEILOMETER AT KMRY IS OUT THIS MORNING... BUT VISIBILITY SENSOR AND MANUAL OBSERVATIONS CONFIRM FOG WITH LIKELY VV001-VV002 CIGS THIS MORNING. FORT ORD PROFILER AND GOESW SATELLITE PRODUCT INDICATING CLOUD THICKNESS IS AROUND 500 TO 1000 FT WHICH IS THINNER THAN PREVIOUS MORNING. WILL LIKELY SEE EARLY MIX OUT THIS MORNING DUE TO SHALLOWER LAYER AND ADDITIONAL MIXING. DRIZZLE POSSIBLE ALONG THE COAST. IFR CIGS CONTINUE TONIGHT. VICINITY OF KSFO...IFR CIGS CLEARING AFTER 18Z. ONSHORE WINDS THROUGH THE DAY WITH GUSTS UP TO 25 KT THIS AFTERNOON. KSFO BRIDGE APPROACH...SIMILAR TO KSFO. MONTEREY BAY AREA TERMINALS...IFR CIGS CLEARING AFTER 18Z AT SNS. LOW CONFIDENCE FOR MRY AS THE CIGS MAY BECOME SCT IN THE AFTERNOON ALLOWING FOR SOME BRIEF VFR CONDITIONS. && .MARINE...AS OF 04:25 AM PDT SATURDAY...HIGH PRESSURE SHIFTS INLAND AND IS REPLACED BY A WEAK LOW PRESSURE OVER THE COASTAL WATERS. WINDS WEAKEN THROUGH THE WEEKEND WITH THE STRONGEST WINDS THROUGH THE NORTHERN SAN FRANCISCO BAY... SONOMA COASTLINE... AND BIG SUR COASTLINE. NORTHWEST WINDS INCREASE AND SEAS BUILD MIDWEEK INTO NEXT WEEKEND. && .MTR WATCHES/WARNINGS/ADVISORIES... .TDAY...NONE. $$ PUBLIC FORECAST: RWW AVIATION/MARINE: DRP VISIT US AT WEATHER.GOV/SANFRANCISCO FOLLOW US ON FACEBOOK, TWITTER, AND YOUTUBE AT: WWW.FACEBOOK.COM/NWSBAYAREA WWW.TWITTER.COM/NWSBAYAREA WWW.YOUTUBE.COM/NWSBAYAREA  FXUS66 KMTR 010547 AFDMTR AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA 1047 PM PDT FRI JUL 31 2015 .SYNOPSIS...A COOLING TREND IS EXPECTED TO CONTINUE INTO THE WEEKEND AS ONSHORE FLOW INCREASES AND THE MARINE LAYER DEEPENS. SUBTROPICAL MOISTURE WILL MOVE OUT OF OUR AREA OVERNIGHT AND ISOLATED THUNDERSTORMS ARE NO LONGER EXPECTED. && .DISCUSSION...AS OF 8:55 PM PDT FRIDAY...THE SHORTWAVE TROUGH THAT TRIGGERED ISOLATED SHOWERS AND THUNDERSTORMS ACROSS OUR AREA TODAY HAS MOVED WELL TO OUR NORTH THIS EVENING. RADAR HAS DETECTED NO ADDITIONAL CONVECTIVE PRECIP ACTIVITY SINCE EARLY EVENING. A FORECAST UPDATE WAS RECENTLY COMPLETED TO REMOVE ALL MENTION OF SHOWERS AND THUNDERSTORMS FOR THIS EVENING. DRIER AIR WILL MOVE INTO THE MID AND UPPER LEVELS OF THE ATMOSPHERE TONIGHT AND SATURDAY AS THE MID/UPPER FLOW VEERS FROM SOUTHEAST TO SOUTHWEST. THUS...CONVECTIVE PRECIPITATION IS NO LONGER A POSSIBILITY...AT LEAST NOT THROUGH OUR CURRENT FORECAST PERIOD. THE COOLING TREND THAT GOT UNDERWAY ON THURSDAY CONTINUED TODAY AS SOUTHERLY FLOW AND A DEEPER MARINE LAYER ALLOWED MARINE AIR TO INFILTRATE FARTHER INLAND. THE LIVERMORE AIRPORT'S HIGH OF 87 TODAY WAS 20 DEGREES COOLER THAN WEDNESDAY'S HIGH OF 107. TEMPERATURES ARE EXPECTED TO CONTINUE THEIR DOWNWARD TREND THROUGH THE WEEKEND...ALBEIT AT A SLOWER PACE...AS THE UPPER RIDGE OVER THE WESTERN CONUS SHIFTS EASTWARD AND A TROUGH REMAINS OFF THE WEST COAST. ALSO...LOW LEVEL ONSHORE FLOW IS FORECAST TO INCREASE A BIT MORE OVER THE WEEKEND. MOST INLAND VALLEY LOCATIONS WILL SEE TEMPERATURES AT LEAST SLIGHTLY BELOW NORMAL THROUGH THE WEEKEND. MILD TEMPERATURES WILL THEN CONTINUE THROUGH NEXT WEEK AS THE UPPER TROUGH OFFSHORE ADVANCES ON THE WEST COAST. FORT ORD PROFILER DATA INDICATE THAT THE MARINE LAYER HAS DEEPENED PAST 2000 FEET THIS EVENING. WOULD THEREFORE EXPECT WIDESPREAD LOW CLOUDS AND PATCHY FOG TO DEVELOP OVERNIGHT AND INTO EARLY SATURDAY. MOST INLAND AREAS WILL CLEAR BY MIDDAY TOMORROW AND SUNDAY...BUT EXPECT AT LEAST AREAS OF LOW CLOUDS TO PERSIST NEAR THE OCEAN THROUGH THE AFTERNOON HOURS. && .AVIATION...AS OF 10:50 PM PDT FRIDAY...PLENTY OF LOW CLOUDS ARE IMPACTING THE TERMINALS TONIGHT. THE CURRENT GOES MVFR PROBABILITY PRODUCT IS SHOWING STRATUS PENETRATING BOTH SAN FRANCISCO AND MONTEREY BAYS AS WELL AS NORTHERN PORTIONS OF THE SALINAS VALLEY. ACCORDING TO THE FORT ORD PROFILER THE MARINE LAYER HAS BECOME PRETTY SOLID AT A DEPTH OF 2000 FEET. WITH THE MOIST BOUNDARY LAYER AND THIS DEEP MARINE LAYER IN PLACE TOMORROWS STRATUS BURNOFF COULD STICK AROUND A LITTLE BIT LONGER THAN TYPICAL. VICINITY OF KSFO...BKN-OVC015 IS IN PLACE OVER THE TERMINALS TONIGHT. CIGS ARE EXPECTED TO DETERIORATE TO OVC008 BY 1200Z. FIRST GUESS AT THE MORNING BURN OFF IS 1830Z. CONFIDENCE IS MODERATE. KSFO BRIDGE APPROACH...SIMILAR TO KSFO. MONTEREY BAY AREA TERMINALS...CURRENTLY OVC009 AT MONTEREY CONDITIONS ARE EXPECTED TO CONTINUE TO DETERIORATE TO AROUND 600 FEET BY 1000Z WITH A PERIOD OF 3SM BR BKN003 POSSIBLE BETWEEN 1200 AND 1600Z. CONFIDENCE IS MODERATE. && .MARINE...AS OF 8:50 PM PDT FRIDAY...A WEAK ONSHORE SURFACE PRESSURE GRADIENT WILL MAINTAIN GENERALLY LIGHT WINDS AND GENTLE SEAS THROUGH THE WEEKEND. ALTHOUGH...GENERALLY LIGHT WINDS ARE EXPECTED TO PREVAIL PLEASE KEEP IN MIND THAT THE AFTERNOON SEA BREEZE CAN BE GUSTY THIS TIME OF THE YEAR. && .MTR WATCHES/WARNINGS/ADVISORIES... .TDAY...SCA...SF BAY UNTIL 11 PM && $$ PUBLIC FORECAST: DYKEMA AVIATION: LARRY MARINE: DRP VISIT US AT WWW.WEATHER.GOV/SANFRANCISCO FOLLOW US ON FACEBOOK AND TWITTER AT: WWW.FACEBOOK.COM/NWSBAYAREA WWW.TWITTER.COM/NWSBAYAREA  FXUS66 KMTR 191134 AFDMTR AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA 434 AM PDT WED AUG 19 2015 .SYNOPSIS...ASIDE FROM PATCHY MORNING DRIZZLE DURING THE NEXT FEW DAYS...DRY WEATHER CONDITIONS WILL PERSIST ACROSS THE REGION THROUGH THE UPCOMING WEEKEND. TEMPERATURES WILL SLIGHTLY COOL ALTHOUGH WILL REMAIN NEAR SEASONAL AVERAGES THROUGH THE FORECAST PERIOD. && .DISCUSSION...AS OF 3:15 AM PDT WEDNESDAY...STRAIGHT-FORWARD FORECAST PACKAGE TODAY. WITH THE MARINE LAYER NOW OVER 2000 FEET PLUS THE FLOW AT THE SURFACE GENERALLY FROM THE WEST WIDESPREAD CLOUDS WITH PATCHY DRIZZLE HAVE RETURNED TO THE COAST OVERNIGHT PLUS ALL ADJACENT VALLEYS. IN FACT...THAT WILL BE THE STORY FOR THE REST OF THE WEEK AS LITTLE WILL CHANGE SYNOPTICALLY. HIGHS WILL SLIGHTLY COOL THE NEXT COUPLE OF DAYS ESPECIALLY FOR INLAND SPOTS. DAYTIME TEMPS WILL GENERALLY BE IN THE 60S AND 70S AT THE COAST WITH 80S INLAND. LONGER RANGE GUIDANCE THROUGH NEXT WEEK INDICATES A LONGWAVE TROF STRETCHING FROM CANADA TO OFF THE NORCAL COAST. THIS WILL KEEP THE VERY WARM TO HOT READINGS PLUS MONSOONAL MOISTURE WELL TO OUR EAST AND SOUTH. DO NOT ANTICIPATE ANY WEATHER RELATED HAZARDS FOR THE NEXT 10 DAYS. && .AVIATION...AS OF 04:35 AM PDT WEDNESDAY... MARINE LAYER PUSHED FURTHER INLAND THIS MORNING... EXPANDING DEEP INTO INLAND VALLEYS. GOES CLOUD THICKNESS PRODUCT SHOWING GRADUAL THICKENING OF LAYER OVER THE REGION...WITH THICKNESSES AROUND 800FT ON THE EDGE AND UP TO 1250FT CLOSER TO THE COAST. THE LAYER IS FAIRLY UNIFORM EXCEPT FOR A SMALL HOLE DIRECTLY OVER THE SAN BRUNO GAP/KSFO TERMINAL. KSFO REPORTING FEW TO CLEAR HOWEVER APPROACH IS REPORTING OVC015 TO OVC020. LAYER WILL LIKELY FILL IN AROUND KSFO TERMINAL BEFORE MIXING OUT BY 1630-17Z. LIGHT ONSHORE WINDS TODAY. MARINE LAYER RETURNS TONIGHT. VICINITY OF KSFO...CURRENTLY VFR DIRECTLY OVER TERMINAL HOWEVER MVFR CIGS 1500-2000FT SURROUND TERMINAL ON NORTH/SOUTH/EAST PERIPHERY. LOW CONFIDENCE ON HOLE OVER KSFO FILLING IN. EITHER WAY... MIX OUT OF MARINE LAYER IN VICINITY BY 1630-17Z. KSFO BRIDGE APPROACH...SIMILAR TO KSFO. MIX OUT BY 17-1730Z. MONTEREY BAY AREA TERMINALS...MVFR THROUGH 18Z AT MOST LOCATIONS. LIGHT ONSHORE WINDS TODAY. MVFR/IFR CIGS RETURN AFTER 01-02Z THU. && .MARINE...AS OF 3:15 PM PDT TUESDAY...CALM SEAS AND LIGHT WINDS CONTINUE OVER THE OUTER WATERS THROUGH TOMORROW BEFORE WINDS BEGIN TO GRADUALLY INCREASE THURSDAY AND FRIDAY AS THE ONSHORE GRADIENT INCREASES. WINDS WILL BE STRONGEST THROUGH THE SAN FRANCISCO BAY NORTH OF THE BAY BRIDGE TOMORROW AFTERNOON. && .MTR WATCHES/WARNINGS/ADVISORIES... .TDAY...SCA...SF BAY FROM 2 PM && $$ PUBLIC FORECAST: BELL AVIATION: DRP MARINE: DRP VISIT US AT WWW.WEATHER.GOV/SANFRANCISCO FOLLOW US ON FACEBOOK AND TWITTER AT: WWW.FACEBOOK.COM/NWSBAYAREA WWW.TWITTER.COM/NWSBAYAREA  FXUS66 KMTR 221152 AFDMTR AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA 452 AM PDT SAT AUG 22 2015 .SYNOPSIS...A DEEP MARINE LAYER ALONG THE COAST ALONG WITH NEAR OR SLIGHTLY BELOW SEASONAL TEMPERATURES ARE EXPECTED THROUGH NEXT WEEK AS A WEAK RIDGE OF HIGH PRESSURE PERSISTS OVER THE REGION. && .DISCUSSION...AS OF 4:00 AM PDT SATURDAY...THE MARINE LAYER DEEPENED TO AROUND 2500 FEET OVERNIGHT ALLOWING LOW CLOUDS TO PENETRATE WELL INLAND ONCE AGAIN. CONDITIONS WILL BE SIMILAR TO WHAT HAS BEEN OBSERVED OVER THE LAST FEW DAYS AS THERE IS LITTLE CHANGE EXPECTED TO THE OVERALL SYNOPTIC PATTERN OVER THE AREA. AT THIS HOUR SATELLITE IMAGERY REVEALS WIDESPREAD LOW CLOUDS ACROSS MOST OF THE FORECAST AREA BELOW 2500 FEET. LOW CLOUDS WILL CLEAR TO THE COAST BY MIDDAY WITH SUNNY/CLEAR SKIES EXPECTED ACROSS THE WARNING AREA. LIGHT ONSHORE FLOW WILL PERSIST THROUGH THIS MORNING WITH SLIGHTLY STRONGER WINDS EXPECTED THROUGH THE AFTERNOON AND EVENING HOURS. A RIDGE OF HIGH PRESSURE SITUATED OVER THE DESERT SOUTHWEST WILL PERSIST MUCH OF THE WEEK WITH FORECAST MODELS ALL IN AGREEMENT. THIS WILL RESULT IN LITTLE DEVIATION FROM THE CURRENT FORECAST CONDITIONS. MODELS ARE ALSO BECOMING BETTER ALIGNED THROUGH THE EXTENDED PERIOD AS THE UPPER LEVEL RIDGE AMPLIFIES OVER THE WESTERN U.S. AND AN UPPER LEVEL TROUGH DEEPENS OVER THE EASTERN PACIFIC. EARLIER FORECAST SOLUTIONS OF THE ECMWF HAD THE DEVELOPMENT OF THE TROUGH A BIT FURTHER EAST WHICH WOULD HAVE BROUGHT A CHANCE OF RAIN TO AREA NEXT WEEKEND. HOWEVER THE ECMWF HAS FALLEN INTO LINE WITH THE GFS SOLUTION WHICH HAS THE TROUGH DEEPENING NEAR 40N/140W. THE WETTER ECMWF SOLUTION WOULD HAVE HELPED FIRE FIGHTING EFFORTS IN THE WEST BY BRINGING MUCH NEEDED RAIN, COOLER TEMPERATURES AND HIGH HUMIDITIES. THE GFS SOLUTION WHICH KEEPS THE TROUGH OFF THE COAST WILL MEAN MORE OF THE SAME WITH NEAR NORMAL TEMPERATURES AND CONTINUED DRY CONDITIONS. WE WILL CONTINUE TO MONITOR THE MODELS AS THEY COME TO A CONSENSUS WITH REGARDS TO TIMING AND STRENGTH OF THESE FEATURES. && .AVIATION...AS OF 04:50 AM PDT SATURDAY...SIMILAR SETUP TO THE LAST SEVERAL DAYS... WITH A ROBUST MARINE LAYER AOA 2500 FT DEEP... INTRUDING INLAND... WITH SMALL HOLES IN THE LAYER... INCLUDING OVER KSFO. WINDS ARE TRENDING WITH A STRONGER SOUTHERLY GRADIENT AND A LIGHTER ONSHORE GRADIENT WHICH MAY HELP TO AID IN MIXING OUT SLIGHTLY SOONER THAN YESTERDAY. CLOUD BASES INLAND HAVE CREPT SLIGHTLY LOWER TONIGHT WITH CIGS RANGING FROM 600FT TO 1700 FT AND HAVE HAD AN EASIER TIME PRODUCING DRIZZLE THUS FAR. GOES CLOUD THICKNESS PRODUCT SHOWS A PERSISTENT LAYER DEPTH INLAND...AOA 1000 TO 1250FT... WHICH IS CONSISTENT WITH THE FORT ORD PROFILER. OVERALL... SIMILAR TO YESTERDAY WITH A FEW INDICATORS POINTING TO SLIGHTLY EARLIER MIX OUT TIMES THAN YESTERDAY. MEDIUM CONFIDENCE. VICINITY OF KSFO...ANOTHER HOLE OVER THE TERMINAL THIS MORNING. INTERMITTENT VFR/MVFR THIS MORNING THROUGH 17Z. ONSHORE WINDS UP TO 15KT THIS AFTERNOON. MODERATE CONFIDENCE. KSFO BRIDGE APPROACH...MVFR CIGS AT KSMB THROUGH 18Z WILL HAMPER AVIATION MORESO THAN CIGS AT THE TERMINAL. MONTEREY BAY AREA TERMINALS... GRADUALLY IMPROVING CIGS AFTER 18Z... VFR BY 19Z. LIGHT ONSHORE WINDS TODAY. EARLY RETURN OF MVFR CIGS AOA 01Z SUN. && .MARINE...AS OF 04:41 AM PDT SATURDAY...WINDS AND SEAS WILL PREDOMINATELY BE LIGHT THROUGH THE WEEKEND AND INTO EARLY NEXT WEEK. A LONGER PERIOD SWELL WILL ENTER THE REGION BY NEXT WEEKEND. && .MTR WATCHES/WARNINGS/ADVISORIES... .TDAY...SCA...PT ARENA TO PIGEON PT 10-60 NM UNTIL 5 AM && $$ PUBLIC FORECAST: CW AVIATION: DRP MARINE: DRP VISIT US AT WWW.WEATHER.GOV/SANFRANCISCO FOLLOW US ON FACEBOOK AND TWITTER AT: WWW.FACEBOOK.COM/NWSBAYAREA WWW.TWITTER.COM/NWSBAYAREA  FXUS66 KMTR 230658 AFDMTR AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA 1058 PM PST SUN NOV 22 2015 .SYNOPSIS...A COOLING TREND WILL BEGIN ON MONDAY AS A DRY TROUGH OF LOW PRESSURE MOVES ACROSS NORTHERN CALIFORNIA. A STRONGER COLD FRONT IS THEN FORECAST TO PUSH THROUGH THE REGION ON TUESDAY AND BRING LIGHT...YET WIDESPREAD PRECIPITATION AND MUCH COOLER TEMPERATURES. CONDITIONS DRY OUT BY THANKSGIVING DAY...YET CHILLY TEMPERATURES ARE EXPECTED AND LIKELY TO PERSIST INTO FRIDAY. && .DISCUSSION...AS OF 8:52 PM PST SUNDAY...THE CURRENT IR SATELLITE IMAGE IS SHOWING HIGH CLOUDS PASSING OVER THE FORECAST AREA THIS EVENING. AT THE SURFACE LOCAL OBSERVATIONS ARE INDICATING NO LOW CLOUDS PRESENT WITH SOME REDUCTION TO VISIBILITY DUE TO HAVE IN THE CONCORD AND LIVERMORE AREA. ALSO EVIDENT ON THE IR SATELLITE IMAGE IS A LOW PRESSURE SYSTEM CURRENTLY CENTERED APPROXIMATELY 300 MILES OFF OF THE CALIFORNIA COAST. THIS LOW IS ANTICIPATED TO PASS OVER CENTRAL AND NORTHERN CALIFORNIA ON MONDAY RESULTING IN COOLER TEMPERATURES AND BREEZY CONDITIONS IN THE AFTERNOON HOURS. A STRONGER TROUGH OF LOW PRESSURE IS EVIDENT ON THE CURRENT SATELLITE WATER VAPOUR IMAGE...CENTERED JUST OFF THE BRITISH COLUMBIA COAST. THE 0000Z GFS40 AND 1200Z ECMWF HAVE INITIALIZED WELL WITH THIS TROUGH OF LOW PRESSURE SLIDING IT DOWN THE COAST...IMPACTING NORTHERN AND CENTRAL CALIFORNIA BY LATE TUESDAY MORNING...REACHING THE MONTEREY AREA TUESDAY AFTERNOON. THE COLD CORE OF THE LOW PRESSURE SYSTEM WILL PASS OVER THE TUESDAY NIGHT BRINGING THE COLDEST TEMPERATURES OF THE SEASON SO FAR. ALTHOUGH PRECIPITATION IS EXPECTED TO END BY WEDNESDAY EVENING THESE COLD TEMPERATURES WILL STICK AROUND INTO THE WEEKEND. THE CURRENT FORECAST PACKAGE HANDLES THIS WEATHER SCENARIO WELL AND NO FURTHER UPDATES ARE NEEDED THIS EVENING. PREVIOUS DISCUSSION...AS OF 01:57 PM PST SUNDAY...TEMPERATURES THIS AFTERNOON ARE ONCE AGAIN WELL ABOVE SEASONAL AVERAGES AS A RESULT OF MID/UPPER LEVEL RIDGING OVER THE REGION. MEANWHILE...AN APPROACHING SHORT-WAVE TROUGH CONTINUES TO ADVECT MID/HIGH LEVEL CLOUDS ACROSS A PORTION OF THE REGION. THIS SYSTEM IS FORECAST TO REMAIN MAINLY DRY AS IT SHIFTS INTO NORTHERN CALIFORNIA LATE TONIGHT INTO MONDAY. THE PRIMARY IMPACT FROM THIS SYSTEM WILL BE AN INCREASE IN HIGH LEVEL CLOUDS AND RETURN TO A MORE PERSISTENT ONSHORE FLOW. THIS WILL ALSO LEAD TO COOLING OF DAYTIME TEMPERATURES ON MONDAY...GENERALLY 5 TO 10 DEGREES COOLER COMPARED TO THIS WEEKEND. THE MOST SIGNIFICANT COOL DOWN IS EXPECTED NEAR THE COAST WHERE THE MARINE INFLUENCE INCREASES AND LOW CLOUDS POSSIBLY RETURN. THE MAIN DRIVING FORCE FOR PUSHING THE AFOREMENTIONED SHORT-WAVE TROUGH INLAND IS A STRONGER MID/UPPER LEVEL TROUGH DEVELOPING OVER THE GULF OF ALASKA. THIS SYSTEM IS FORECAST TO DEVELOP A CLOSED LOW LATE MONDAY THAT WILL DROP SOUTHWARD DOWN THE WEST COAST. AS A RESULT...A COLD FRONT IS EXPECTED TO PUSH INTO THE NORTH BAY EARLY TUESDAY MORNING AND SWEEP SOUTHWARD THROUGH THE REMAINDER OF THE MORNING. GENERALLY SPEAKING...RAINFALL AMOUNTS ARE FORECAST TO BE LIGHT AS THE MOISTURE WILL BE LIMITED ACROSS OUR REGION...BEST TO OUR NORTH AND EAST. POST-FRONTAL SHOWERS WILL BE LIKELY IN WAKE OF THE FRONTAL PASSAGE AND CONTINUE INTO WEDNESDAY MORNING. TEMPERATURES WILL ALSO TURN NOTICEABLY COOLER ON TUESDAY...LIKELY TO ONLY WARM INTO THE 50S OR LOWER 60S. AS THE MUCH COLDER AIR MASS FILTERS INTO THE REGION TUESDAY INTO WEDNESDAY...SNOW LEVELS ARE ALSO FORECAST TO DROP TO BELOW 3000FT BY WEDNESDAY MORNING. AS A RESULT...SOME OF THE HIGHER PEAKS ACROSS THE REGION COULD PICK UP AN INCH OR TWO OF SNOWFALL THROUGH WEDNESDAY MORNING. TIMING OF THE COLD AIR ADVECTION AND POTENTIAL SHOWER ACTIVITY WILL BE THE MAIN CHALLENGE WITH RESPECT TO SNOW FALL OVER THE REGION. PRECIPITATION IS FORECAST TO COME TO AN END BY LATE WEDNESDAY AFTERNOON AS THE MAIN MID/UPPER LEVEL SYSTEM AND ASSOCIATED MOISTURE SHIFTS WELL INLAND. RAINFALL AMOUNTS FROM THIS SYSTEM WILL GENERALLY RANGE FROM AROUND A TENTH OF AN INCH TO A QUARTER OF AN INCH...GREATEST AMOUNTS LIKELY IN THE COASTAL RANGES. ALONG WITH THE PRECIPITATION CHANCES AND SIGNIFICANT COOL DOWN...WIND SPEEDS WILL ALSO INCREASE AND RESULTED IN BLUSTERY CONDITIONS TUESDAY AFTERNOON INTO TUESDAY EVENING. THE STRONGEST WINDS APPEAR TO BE NEAR THE COAST WHERE LOCAL GUSTS OF 30 TO 40 MPH WILL BE POSSIBLE. BY WEDNESDAY NIGHT...WINDS DIMINISH AND CLEARING BEGINS OVER THE REGION. THIS WILL ALLOW FOR TEMPERATURES FALL INTO THE 30S OVER MOST VALLEY LOCATIONS AND EVEN UPPER 30S NEAR THE MONTEREY BAY COAST. MEANWHILE...SAN FRANCISCO WILL LIKELY SEE TEMPERATURES FALL INTO THE 40S BY THURSDAY AND FRIDAY MORNINGS. WILL NEED TO CLOSELY MONITOR FOR THE NEED FOR FREEZE WARNINGS OVER THE AT LEAST THE COLDEST INLAND VALLEYS. COOL AND DRY CONDITIONS ARE FORECAST TO PERSIST THROUGH THANKSGIVING DAY AND INTO FRIDAY WITH THE MID/UPPER LEVEL TROUGH STRETCHED ACROSS THE REGION. THOSE WITH OUTDOOR PLANS SHOULD BE PREPARED FOR MUCH COLDER TEMPERATURES LATE THIS WEEK AND CLOSELY MONITOR THE FORECAST FOR POTENTIAL FREEZING TEMPERATURES. FORECAST CONFIDENCE REMAINS LOW IN THE EXTENDED YET ANOTHER WEAK COLD UPPER LEVEL SYSTEM MAY BRING PRECIPITATION BACK TO THE CENTRAL COAST BY SATURDAY. WILL CONTINUE TO MONITOR THE LATEST FORECAST GUIDANCE IN THE COMING DAYS TO SEE IF THEY CONVERGE ON A MORE SIMILAR SOLUTION. REGARDLESS...DO EXPECTED NEAR OR SLIGHTLY BELOW SEASONAL TEMPERATURES FOR NEXT WEEKEND AND THE POTENTIAL FOR UNSETTLED CONDITIONS. && .AVIATION...AS OF 10:58 PM PST SUNDAY...WINDS ARE MAINLY LIGHT OFFSHORE AND VFR PERSISTS THIS EVENING. THE FORT ORD AND BODEGA PROFILERS STILL SHOW WELL DEVELOPED MARINE INVERSIONS. MARINE INVERSIONS REMAIN SHALLOW WITH BASES WELL UNDER 1000 FEET...BUT STEADY COOLING ARRIVING IN THE LOWER LEVELS LATE TONIGHT THROUGH MONDAY WILL LIFT AND WEAKEN THE INVERSIONS. GOES-E SATELLITE LIFR PROB SHOWS A NORTH-SOUTH BAND OF LOW CLOUDS AND FOG ABOUT 70-90 MILES OFFSHORE...MOVING EAST. IN ADDITION TO LOW LEVEL COOLING BRINGING THE AIR CLOSER TO SATURATION LATE TONIGHT AND MONDAY MORNING...THIS BAND OFFSHORE IS ALSO LIKELY TO REACH THE IMMEDIATE COAST BEFORE DAYBREAK MONDAY. OVERALL CONFIDENCE REGARDING CLOUD COVER AND SURFACE WINDS MONDAY IS STILL A BIT SHAKY...FORECAST FACTORS IN WEAKENING INVERSIONS. THEN ADD IN THE COMPACT AND DYNAMIC EPAC UPPER LEVEL LOW CENTER PASSING OVER THE NORTH BAY MONDAY AND CONFIDENCE LOWERS A BIT MORE. MODELS ARE ONLY SHOWING VERY ISOLATED VERY LIGHT AMOUNTS OF PRECIP -MAJORITY OF THE AREA IS DRY- AS THE SYSTEM APPEARS TO BE MOISTURE STARVED. AT THIS POINT ONLY MADE MINOR ADJUSTMENTS TO TAFS TO ADD IN SOME LOW TO MID CLOUD LAYERS AS WELL AS VICINITY SHOWERS (VCSH). SURFACE WINDS MAY BECOME LOCALLY GUSTY BY MONDAY AFTERNOON AND EVENING. A SEPARATE COLDER LOW FROM ALASKA ARRIVES TUESDAY AND WEDNESDAY. FREEZING LEVELS LOWER TO 3500-4000 FEET BY TUE EVENING/NIGHT PER SOUNDING FORECASTS. VICINITY OF KSFO...VFR AND LIGHT/VARIABLE WINDS CONTINUE DURING THE OVERNIGHT HOURS. WINDS SHIFTING TO LIGHT SE MONDAY MORNING. COMPACT LOW CENTER PASSES OVER THE NORTH BAY MONDAY...MAYBE A FEW SHOWERS AT KSFO? CLOUD BASES SHOULD BE ELEVATED ENOUGH FOR VFR TO PERSIST MONDAY. POTENTIAL THERE FOR WESTERLY WIND GUSTS UP TO 20 KNOTS BY MONDAY AFTERNOON AND EVENING. KSFO BRIDGE APPROACH...SIMILAR TO KSFO. MONTEREY BAY AREA TERMINALS...VFR AND LIGHT SE WINDS. SE WINDS COULD BE UPWARDS OF 10 KNOTS LATE TONIGHT/MONDAY MORNING KSNS. LOWER CONFIDENCE CLOUD FORECAST EARLY MONDAY. 06Z TAFS WILL BE AMENDED TO INLUDE TEMPO IFR FOR MONDAY MORNING. VCSH LATE MONDAY MORNING INTO THE AFTERNOON. && .MARINE...AS OF 01:57 PM PST SUNDAY...LIGHT TO MODERATE NORTHERLY WINDS WILL CONTINUE THROUGH MONDAY OVER THE COASTAL WATERS. A RELATIVELY SMALL NORTHWESTERLY SWELL WILL ALSO PREVAIL THROUGH MONDAY. A STORM SYSTEM WILL IMPACT THE COASTAL WATERS TUESDAY AND WEDNESDAY BRINGING...INCREASING WINDS...BUILDING SEAS...PERIODS OF RAIN AND HAZARDOUS CONDITIONS. && .MTR WATCHES/WARNINGS/ADVISORIES... .TNGT...NONE. $$ PUBLIC FORECAST: LARRY/GASS AVIATION: CANEPA MARINE: MM VISIT US AT WWW.WEATHER.GOV/SANFRANCISCO FOLLOW US ON FACEBOOK AND TWITTER AT: WWW.FACEBOOK.COM/NWSBAYAREA WWW.TWITTER.COM/NWSBAYAREA  FXUS66 KMTR 301259 AFDMTR AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA 459 AM PST MON NOV 30 2015 .SYNOPSIS...A WEAK FRONTAL SYSTEM MAY PRODUCE LIGHT RAIN TODAY...MAINLY NEAR THE COAST AND IN THE NORTH BAY. OTHERWISE DRY WEATHER IS EXPECTED THROUGH WEDNESDAY ALONG WITH WARMER TEMPERATURES. A STRONGER PACIFIC STORM WILL LIKELY BRING RAIN AND GUSTY WINDS TO THE REGION ON THURSDAY. && .DISCUSSION...AS OF 3:50 AM PST MONDAY...BY 2 AM TEMPERATURES HAD ALREADY DROPPED BELOW FREEZING AT SEVERAL INLAND LOCATIONS AND INTO THE UPPER 20S IN SOME SPOTS. HIGH CLOUDS AHEAD OF THE INCOMING WEAK FRONTAL SYSTEM ARE BEGINNING TO SPREAD ACROSS THE NORTHERN PORTION OF OUR AREA THIS TIME...WHICH ALREADY APPEARS TO BE BRINGING THE COOLING TO A HALT IN THE NORTH BAY. BUT FARTHER SOUTH...SKIES SHOULD REMAIN MOSTLY CLEAR FOR THE NEXT FEW HOURS WHICH WILL ALLOW FOR FURTHER COOLING PRIOR TO SUNRISE. WILL KEEP THE FREEZE WARNING GOING FOR NOW...ALTHOUGH IT'S POSSIBLE THE WARNING COULD BE CANCELLED PRIOR TO 9 AM AS THE FRONT DRAWS CLOSER AND WARMER AIR BEGINS TO MIX INTO THE BOUNDARY LAYER. THIS WILL BE OUR LAST COLD NIGHT. THE INCOMING FRONT DOES NOT YET SHOW SIGNS OF WEAKENING AND A NARROW BAND OF PRECIPITABLE WATER VALUES NEAR 1 INCH CONTINUE TO BE DETECTED ALONG THE FRONT. IT'S STILL LIKELY THAT THE FRONT WILL WEAKEN AS IT CONTINUES TO PUSH EASTWARD AND INTO THE DRY AIRMASS CURRENTLY OVER CALIFORNIA. BUT RECENT MODEL OUTPUT INDICATES THERE IS A DECENT CHANCE THAT COASTAL AREAS FROM SANTA CRUZ COUNTY NORTHWARD WILL SEE SOME LIGHT RAIN TODAY. BASED ON THE LATEST HRRR...LIGHT RAIN WILL REACH THE NORTH BAY COAST BY MID MORNING...AND SAN FRANCISCO AND SAN MATEO COUNTY EARLY IN THE AFTERNOON. MOST INLAND AREAS ARE EXPECTED TO REMAIN DRY. POPS HAVE BEEN INCREASED IN COASTAL AREAS TODAY. RAINFALL AMOUNTS TODAY ARE FORECAST TO BE LESS THAN A TENTH OF AN INCH. A FEW SPRINKLES OR LIGHT SHOWERS MAY LINGER THROUGH THE EARLY EVENING...BUT DRY WEATHER IS EXPECTED TO DEVELOP BY TONIGHT. DRY WEATHER IS THEN FORECAST TO CONTINUE FOR TUESDAY AND WEDNESDAY...ALONG WITH A WARMING TREND AS A SHORTWAVE RIDGE DEVELOPS OVER CALIFORNIA. THE MODELS AGREE IN BRINGING A RELATIVELY ROBUST PACIFIC WEATHER SYSTEM INTO NORTHERN CALIFORNIA ON THURSDAY...ALTHOUGH THERE ARE SOME DIFFERENCES ON TIMING. A MOIST SOUTHWESTERLY FLOW IS FORECAST TO DEVELOP ACROSS NORTHWEST CALIFORNIA AS EARLY AS TUESDAY NIGHT...AND THE 00Z ECMWF DEVELOPS SOME WARM ADVECTION PRECIP AS FAR SOUTH AS SONOMA COUNTY BY WEDNESDAY MORNING. HOWEVER...THE NAM AND GFS KEEP THIS MOISTURE TO THE NORTH OF OUR AREA. RAIN CHANCES WON'T INCREASE SIGNIFICANTLY FOR MOST OF OUR AREA UNTIL THURSDAY WHEN THE UPPER TROUGH APPROACHES NORTHERN CALIFORNIA. THE ECMWF IS FASTER AND SPREADS THE BULK OF THE PRECIPITATION ACROSS OUR AREA ON THURSDAY MORNING...WHILE THE GFS AND NAM HOLD OFF UNTIL THURSDAY AFTERNOON. ASIDE FROM THESE TIMING DIFFERENCES...THE MODELS AGREE THAT THIS SYSTEM WILL BE CAPABLE OF PRODUCING AT LEAST A SHORT PERIOD OF MODERATE TO LOCALLY HEAVY RAIN RATES AS IT PUSHES THROUGH ON THURSDAY. BUT BECAUSE THE SYSTEM IS FORECAST TO MOVE THROUGH RELATIVELY QUICKLY...OVERALL RAINFALL AMOUNTS ARE NOT EXPECTED TO EXCEED AN INCH IN MOST AREAS. MODEL QPF FOR THE THURSDAY EVENT IS GENERALLY BETWEEN A HALF INCH AND AN INCH IN THE SF BAY AREA AND SANTA CRUZ COUNTY...AND ABOUT A THIRD OF AN INCH OF LESS FOR MONTEREY AND SAN BENITO COUNTIES. AT LEAST A FEW HOURS OF STRONG WINDS ARE EXPECTED WITH THIS SYSTEM AS THE FRONT MOVES THROUGH ON THURSDAY. THE MODELS FORECAST A SURFACE LOW OF ABOUT 990 MB WEST OF CAPE MENDOCINO ON THURSDAY...WHICH WOULD RESULT IN WIND GUSTS OF UP TO 50 MPH OR MORE ALONG THE COAST AND IN THE HILLS. WIND ADVISORIES MAY BE NEEDED LATE WEDNESDAY NIGHT INTO THURSDAY. SHOWERS ARE FORECAST TO CONTINUE INTO THURSDAY NIGHT...AND MOSTLY END BY FRIDAY. DRY AND MILD WEATHER IS FORECAST FOR SATURDAY...WITH THE NEXT SYSTEM POSSIBLY BRINGING ANOTHER ROUND OF RAIN INTO OUR REGION BY LATE IN THE WEEKEND. && .AVIATION...AS OF 4:59 AM PST MONDAY...A WEAKENING UPPER LEVEL TROUGH OVER THE EPAC MOVES EAST OVER NORCAL TODAY. A COOL FRONT WILL ACCOMPANY THE TROUGH HOWEVER IT IS ALSO WEAKENING...BUT THERE MAY STILL BE A FEW SHOWERS AROUND THE AREA TODAY. THE UPPER LEVEL RIDGE WILL BUILD BACK OVER THE AREA TONIGHT THROUGH TUESDAY. THE 12Z OAKLAND SOUNDING INDICATES A DRY LAYER PERSISTING FROM THE SURFACE UP TO ALMOST 10K FEET THIS MORNING THEN IT'S SOMEWHAT MORE MOIST FROM 10K-13K FEET. GOES SATELLITE LIFR PROBABILITY AND AREA METARS BOTH INDICATE VFR THUS HIGH CONFIDENCE VFR CONTINUES TODAY BASED ON THIS. THE MODEL FORECAST SOUNDINGS SHOW A STEADY INCREASE IN MID LEVEL CLOUDINESS TODAY WHICH GRADUALLY LOWERS TO MVFR CATEGORY LATE TODAY...12Z TAFS CONTINUE TO GENERALLY FOLLOW THIS IDEA. VICINITY OF KSFO...LIGHT WINDS AND VFR TODAY. VCSH 22Z-02Z...MODERATE CONFIDENCE MVFR CIG BY 02Z THIS EVENING. KSFO BRIDGE APPROACH...SIMILAR TO KSFO. MONTEREY BAY AREA TERMINALS...SE WINDS ARE A LITTLE MORE ROBUST THIS MORNING AT KSNS AND KMRY DUE TO COMBINED NIGHT-TIME COOLING/DRAINAGE WINDS AS WELL AS SOME OVERLAP ENHANCEMENT POSSIBLE BY THE APPROACHING EPAC TROUGH. HIGH CONFIDENCE VFR TODAY AND TONIGHT. SURFACE WINDS BECOMING VARIABLE BY MID-LATE AFTERNOON. && .MARINE...AS OF 3:15 AM PST MONDAY...A WEAK FRONTAL SYSTEM WILL DISSIPATE OVER THE COASTAL WATERS TODAY. A STRONGER FRONTAL SYSTEM APPROACHES THE AREA MID-WEEK. LARGER SWELL HEIGHTS WILL ARRIVE LATE IN THE WEEK. && .MTR WATCHES/WARNINGS/ADVISORIES... .TDAY...FREEZE WARNING...INLAND VALLEYS AND MOUNTAINS UNTIL 9 AM. && $$ PUBLIC FORECAST: DYKEMA AVIATION: CANEPA MARINE: CANEPA/W PI VISIT US AT WWW.WEATHER.GOV/SANFRANCISCO FOLLOW US ON FACEBOOK AND TWITTER AT: WWW.FACEBOOK.COM/NWSBAYAREA WWW.TWITTER.COM/NWSBAYAREA  FXUS66 KMTR 180554 AFDMTR AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA 1054 PM PDT THU MAR 17 2016 .SYNOPSIS...HIGH PRESSURE ALOFT OVER THE AREA WILL RESULT IN CONTINUED DRY WEATHER CONDITIONS THROUGH FRIDAY. A SHALLOW MARINE LAYER NEAR THE COAST ALONG WITH LIGHT ONSHORE FLOW WILL RESULT IN COOLING IN COASTAL AREAS ON FRIDAY...BUT INLAND AREAS WILL REMAIN UNSEASONABLY WARM FOR ONE MORE DAYS. TEMPERATURES ARE EXPECTED TO COOL IN ALL AREAS OVER THE WEEKEND AS AN UPPER LEVEL TROUGH SETTLES IN NEAR THE WEST COAST. RAIN CHANCES WILL BEGIN ON SUNDAY AND CONTINUE INTO TUESDAY. THE BEST POTENTIAL FOR RAIN WILL BE ACROSS THE NORTH. && .DISCUSSION...AS OF 9:05 PM PDT THURSDAY...THE WARMING TREND THAT BEGAN EARLIER THIS WEEK CONTINUED TODAY WITH AFTERNOON HIGHS COMING IN ABOUT FIVE DEGREES WARMER COMPARED TO WEDNESDAY. MOST LOCATIONS POSTED HIGHS IN THE 70S UNDER SUNNY SKIES. SOME SPOTS CLIMBED INTO THE LOWER 80S INCLUDING THE FOLLOWING LOCATIONS: OAKLAND MUSEUM...ANTIOCH...HEALDSBURG...MORGAN HILL...KING CITY...AND PINNACLES NATIONAL PARK. EVEN WITH TODAY'S WARM TEMPERATURES...MOST OF OUR AREA WAS BELOW RECORD HIGHS BY ANYWHERE FROM 5 TO 10 DEGREES. A SHALLOW MARINE LAYER DEVELOPED ALONG THE COAST THIS AFTERNOON. EVENING SATELLITE IMAGERY SHOWS WIDESPREAD LOW CLOUDS NEAR THE OCEAN...AND LOCALLY INLAND FROM MONTEREY BAY. THE MARINE LAYER IS QUITE SHALLOW...ONSHORE FLOW IS WEAK...AND THE AIRMASS ACROSS INLAND AREAS REMAINS DRY. FOR THESE REASONS FEEL IT'S UNLIKELY WE WILL SEE MORE THAN PATCHY LOW CLOUDS AND FOG DEVELOP INLAND OVERNIGHT AND INTO FRIDAY MORNING. PATCHY DENSE FOG IS POSSIBLE. WITH A MARINE LAYER NOW IN PLACE ALONG THE COAST...AND WITH LIGHT ONSHORE FLOW FORECAST TO CONTINUE INTO FRIDAY...EXPECT COOLER CONDITIONS IN COASTAL AREAS TOMORROW. COASTAL TEMPS WILL BE AS MUCH AS 10 DEGREES COOLER COMPARED TO TODAY. INLAND AREAS WILL EXPERIENCE MORE MODEST COOLING...AND SOME OF THE INLAND VALLEYS ISOLATED FROM THE EFFECTS OF A SHALLOW MARINE LAYER WILL PROBABLY SEE TEMPS AROUND PERSISTENCE. MORE WIDESPREAD COOLING WILL OCCUR OVER THE UPCOMING WEEKEND AS THE UPPER RIDGE RESPONSIBLE FOR OUR CURRENT BALMY WEATHER MOVES OFF TO THE EAST AND IS REPLACED BY A TROUGH BY LATE IN THE WEEKEND. IN ADDITION...THAT UPPER TROUGH IS FORECAST TO PRODUCE RAIN AT TIMES ACROSS NORTHERN CALIFORNIA...AND THE NORTHERN PART OF CENTRAL CA...FROM SUNDAY THROUGH TUESDAY. MODEL CONSENSUS INDICATES RAIN WILL DEVELOP IN OUR NORTH BAY COUNTIES BY SUNDAY MORNING AND THEN SPREAD SOUTH ACROSS MOST OF THE REMAINDER OF OUR FORECAST AREA SUNDAY AFTERNOON AND EVENING. PERIODS OF RAIN WILL THEN CONTINUE THROUGH TUESDAY EVENING AS THE UPPER TROUGH SLOWLY TRANSITS OUR AREA. RAINFALL POTENTIAL AND INTENSITY THROUGHOUT THIS PERIOD WILL BE GREATEST ACROSS THE NORTHERN PORTION OF OUR AREA. IN ADDITION...RAINFALL WILL PROBABLY BE HEAVIEST ON SUNDAY AS THE INITIAL IMPULSE MOVES THROUGH...AS THAT IS WHEN PRECIPITABLE WATER VALUES ARE FORECAST TO BE HIGHEST (AROUND 1 INCH). BY TUESDAY WE WILL HAVE TRANSITIONED TO WIDELY SCATTERED SHOWERS. RAINFALL TOTALS FROM SUNDAY THROUGH TUESDAY ARE EXPECTED TO RANGE FROM 0.5-1.5 INCHES IN THE NORTH BAY. SOUTH OF THE GOLDEN GATE MOST LOCATIONS ARE EXPECTED TO SEE A HALF INCH OR LESS. DRY WEATHER IS FORECAST TO RETURN BY THE MIDDLE OF NEXT WEEK...WITH A WARMING TREND EXPECTED DURING THE SECOND HALF OF THE WEEK. && .AVIATION...AS OF 10:53 PM PDT THURSDAY...CURRENTLY THE GOES R IFR PROBABILITY PRODUCT IS SHOWING A HIGH PROBABILITY OF STRATUS ALONG THE COAST AND PUSHING INTO THE SALINAS VALLEY. THE FORT ORD PROFILER IS SHOWING THAT THIS MARINE STRATUS...MARINE LAYER...IS RIGHT AROUND 1000 FEET DEEP. LOCAL OBS FROM HALFMOON BAY AND MONTEREY ARE SHOWING BASES BETWEEN 400 AND 600 FEET DEEP. WITH A TOP AROUND 1000 FEET IT IS DOUBTFUL THAT THE STRATUS WILL PUSH THROUGH SAN BRUNO GAP INTO SAN FRANCISCO BAY...BUT IT WILL PUSH INTO THE GOLDEN GATE WITHIN THE NEXT FEW HOURS AND IS EXPECTED TO IMPACT KOAK OVERNIGHT AND ALSO THE SFO APPROACH BY MORNING. STRATUS IS ALSO ANTICIPATED TO PERSIST OVER THE MONTEREY AND SALINAS TERMINALS OVERNIGHT INTO LATE MORNING AS WELL. VICINITY OF KSFO...VFR CONDITIONS ARE ANTICIPATED TO PREVAIL THROUGH LATE TONIGHT WITH THE POSSIBILITY OF OVC008 BETWEEN 1300Z AND 1700Z FRIDAY MORNING. CONFIDENCE IS MODERATE. KSFO BRIDGE APPROACH...VFR IS ANTICIPATED TO PREVAIL THROUGH LATE TONIGHT WITH BKN-OVC006-008 ANTICIPATED FOR THE MORNING. FIRST GUESS AT MORNING BURN OFF WILL BE 1630Z TO 1700Z. MONTEREY BAY AREA TERMINALS...IFR CONDITIONS EXPECTED TO PREVAIL THROUGH FRIDAY MORNING WITH PERIODS OF DENSE FOG POSSIBLE DURING THE EARLY MORNING HOURS. FIRST GUESS AT MORNING BURN OFF FOR MTR AND SNS IS 1830Z. CONFIDENCE IS MODERATE. && .MARINE...AS OF 8:27 PM PDT THURSDAY...GENERALLY LIGHT WINDS ARE ANTICIPATED TO PREVAIL OVERNIGHT AS A WEAK SURFACE PRESSURE GRADIENT RESIDES ALONG THE COAST. LOCALLY MODERATE AND GUSTY WINDS ARE EXPECTED SOUTH OF POINT SUR FRIDAY AFTERNOON INTO THE EVENING HOURS. OTHERWISE LIGHT WINDS ARE EXPECTED TO PREVAIL THROUGH SATURDAY EVENING WITH STRENGTHENING SOUTHERLY WINDS ON SUNDAY AS A STORM SYSTEM APPROACHES THE COAST. A MODERATE WESTERLY SWELL IS EXPECTED TO ARRIVE THIS WEEKEND WITH A LARGER SWELL ARRIVING EARLY NEXT WEEK. && .MTR WATCHES/WARNINGS/ADVISORIES... .TNGT...NONE. $$ PUBLIC FORECAST: DYKEMA AVIATION: LARRY MARINE: LARRY VISIT US AT WWW.WEATHER.GOV/SANFRANCISCO FOLLOW US ON FACEBOOK AND TWITTER AT: WWW.FACEBOOK.COM/NWSBAYAREA WWW.TWITTER.COM/NWSBAYAREA  FXUS66 KMTR 031651 AFDMTR AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA 951 AM PDT SUN APR 3 2016 .SYNOPSIS...A DRY UPPER TROUGH IS FORECAST TO MOVE INLAND TO OUR NORTH LATE TODAY...BUT THIS TROUGH WILL HAVE LITTLE IMPACT ON OUR WEATHER OTHER THAN SLIGHT COOLING TODAY. STRONG HIGH PRESSURE WILL BUILD OVER THE WEST COAST DURING THE FIRST HALF OF THE WEEK AND OFFSHORE FLOW WILL DEVELOP BY TUESDAY. THIS WILL RESULT IN MUCH WARMER TEMPERATURES BY TUESDAY WITH RECORD HIGHS POSSIBLE BY WEDNESDAY. COOLING IS EXPECTED LATE IN THE WEEK AS AN UPPER LEVEL LOW APPROACHES THE CALIFORNIA COAST. SHOWERS ARE POSSIBLE LATE THURSDAY NIGHT INTO FRIDAY...WITH UNSETTLED WEATHER PERSISTING INTO NEXT WEEKEND. && .DISCUSSION...AS OF 9:51 AM PDT SUNDAY...THE MARINE LAYER DEEPENED OVERNIGHT AND IS NOW APPROACHING 2000 FEET DEEP PER THE FORT ORD PROFILER DATA. VISIBLE SATELLITE IMAGERY SHOWS LOW CLOUDS SOLIDLY FILLING INLAND VALLEYS. GOES CLOUD THICKNESS ESTIMATES INDICATE THICK LAYER OF CLOUD ALONG THE MONTEREY BAY...ON THE ORDER OF 2000-2600 FEET...WHICH WOULD INDICATE A SLOW CLEARING TODAY. COASTAL TEMPERATURES MIGHT BE SLOW TO WARM TODAY GIVEN THE ONSHORE SURFACE PRESSURE GRADIENT IS SLIGHTLY STRONGER THIS MORNING WITH 1.6 MB FROM SFO TO SAC...AND DUE TO LONGER CLOUD COVER. A WEAK UPPER TROUGH WILL APPROACH THE PACIFIC NORTHWEST COAST LATER TODAY...BUT MODELS STILL KEEP PRECIP CHANCES WELL TO THE NORTH OF OUR DISTRICT. ABOUT THE ONLY IMPACT THIS SYSTEM WILL HAVE ON OUR WEATHER IS TO DEEPEN THE MARINE LAYER TODAY...WITH THE RESULT BEING SLIGHTLY COOLER AFTERNOON HIGHS TODAY COMPARED TO YESTERDAY. AN UPPER RIDGE WILL BEGIN TO BUILD OFFSHORE ON MONDAY. A SURFACE HIGH WILL DEVELOP AND MOVE INLAND OVER THE PACIFIC NORTHWEST WHICH WILL WILL RESULT IN GUSTY NORTHWEST WINDS ALONG THE COAST. SLIGHTLY WARMER WEATHER IS EXPECTED ON MONDAY AS INCREASING NORTHERLY GRADIENTS RESULT IN DECREASED MARINE AIR INFLUENCE. THE WARMING TREND THAT WILL START SLOWLY ON MONDAY WILL PICK UP STEAM ON TUESDAY AS THE UPPER RIDGE BUILDS MORE STRONGLY NEAR THE WEST COAST AND THE SURFACE HIGH MOVES INTO THE GREAT BASIN...TURNING THE LOW LEVEL FLOW TOWARDS OFFSHORE. HIGH TEMPERATURES ON TUESDAY ARE FORECAST TO BE ABOUT TEN DEGREES WARMER THAN AVERAGE...WITH THE GREATEST WARMING EXPECTED ON WEDNESDAY WHEN OFFSHORE FLOW IS THE STRONGEST. NEAR RECORD HIGH TEMPERATURES ARE POSSIBLE ON WEDNESDAY WITH WIDESPREAD 80S AND LOWER 90S ARE FORECAST. BECAUSE THIS WILL BE THE FIRST HEAT EVENT OF THE SEASON...THOSE SENSITIVE TO HEAT WILL LIKELY EXPERIENCE GREATER STRESS THAN MIGHT OTHERWISE BE EXPECTED. THIS UPCOMING HEAT EVENT WILL BE SHORT-LIVED AS AN UPPER LOW APPROACHES THE STATE FROM THE SOUTHWEST. COOLING WILL BEGIN ON THURSDAY AS AN UPPER LOW WEST OF BAJA BEGINS TO LIFT TO THE NORTHEAST AND A SECOND SYSTEM APPROACHES FROM THE WEST. THESE TWO SYSTEMS ARE FORECAST TO MERGE...UNDERCUT THE WEST COAST RIDGE...AND MOVE INLAND ACROSS SOUTH-CENTRAL CALIFORNIA DURING THE WEEKEND. SHOWERS MAY BEGIN OVER THE SOUTHERN PORTION OF OUR FORECAST AREA AS EARLY AS THURSDAY NIGHT...AND INCREASE AND SPREAD NORTH OVER MOST OF OUR FORECAST AREA FRIDAY AND SATURDAY AS AN UPPER LOW APPROACHES POINT CONCEPTION. PRECIP CHANCES WILL DECREASE BY LATE IN THE WEEKEND AS THIS LOW MOVES OFF TO THE EAST. UNSETTLED CONDITIONS MAY CONTINUE INTO THE EARLY PART OF NEXT WEEK AS ANOTHER UPPER LOW APPROACHES FROM THE WEST...BUT MODELS ARE NOT IN VERY GOOD AGREEMENT AFTER THE WEEKEND. && .AVIATION...AS OF 4:39 AM PDT SUNDAY...IFR CIGS ALONG THE IMMEDIATE COAST WITH AREAS IFR CIGS INLAND. CLEARING WILL BE GRADUAL DURING MID-LATE MORNING. MARINE INVERSIONS ARE BASED NEAR 1500 FEET THIS MORNING. VICINITY OF KSFO...IFR CIG PARTIALLY CLEARING TO SCT CLOUDS 18Z TODAY. LIGHT WINDS THIS MORNING BECOMING WESTERLY SUSTAINED 15-20 KNOTS THIS AFTERNOON AND EVENING. SFO BRIDGE APPROACH...SIMILAR TO KSFO. MONTEREY BAY TERMINALS...IFR CIGS PARTIALLY CLEARING TO SCT CLOUDS 17Z-18Z TODAY. MAINLY LIGHT ONSHORE WINDS TODAY. && .BEACHES...AS OF 4:33 AM PDT SUNDAY...A LOW AMPLITUDE MODERATE TO HIGH ENERGY MIXED SWELL WILL CONTINUE TO MOVE THROUGH THE WATERS TODAY. THESE ENERGETIC WAVES WILL SUPPORT STRONG RIP CURRENTS AT LOCAL BEACHES WITH THE POTENTIAL FOR LARGE SHORE BREAK AT SOME BEACHES SUCH AS TWIN LAKES BEACH IN SANTA CRUZ. MIXED SWELL WILL SLOWLY SUBSIDE BY THIS EVENING. && .MARINE...AS OF 3:08 AM PDT SUNDAY...A MIXED LONG PERIOD SWELL WILL CONTINUE TODAY. HIGH PRESSURE OVER THE EASTERN PACIFIC WILL BUILD OVER NORTHERN CALIFORNIA THROUGH EARLY THIS WEEK. SURFACE HIGH PRESSURE WILL THEN EXTEND INTO THE GREAT BASIN TUESDAY AND WEDNESDAY. BY THURSDAY THE HIGH WILL HAVE MOVED EAST AND BE LOCATED FROM THE FOUR CORNERS AREA TO THE PACIFIC NORTHWEST. AN UPPER LEVEL LOW PRESSURE AREA WILL DEVELOP NEARLY ONE THOUSAND MILES OFF THE CALIFORNIA COAST THURSDAY THEN THE LOW WILL APPROACH CALIFORNIA VERY LATE IN THE WEEK AND NEXT WEEKEND WITH SHOWERS. && .MTR WATCHES/WARNINGS/ADVISORIES... .TDAY...SCA...SF BAY FROM 2 PM && $$ PUBLIC FORECAST: SIMS AVIATION: CANEPA MARINE: CANEPA VISIT US AT WWW.WEATHER.GOV/SANFRANCISCO FOLLOW US ON FACEBOOK AND TWITTER AT: WWW.FACEBOOK.COM/NWSBAYAREA WWW.TWITTER.COM/NWSBAYAREA  FXUS66 KMTR 040320 AFDMTR AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA 820 PM PDT SUN APR 3 2016 .SYNOPSIS...THE FORECAST AREA REMAINS ON TRACK FOR A SUBSTANTIAL MID WEEK WARM UP AS HIGH PRESSURE BUILDS OVER THE AREA AND LIGHT OFFSHORE WINDS SET UP AT THE SURFACE. TEMPERATURES WILL PEAK WEDNESDAY BEFORE COOLING ON THURSDAY. && .DISCUSSION...AS OF 8:19 PM PDT SUNDAY...SKIES CLEARED OUT NICELY THIS AFTERNOON PROVIDING A MAJORITY OF THE FORECAST AREA WITH AT LEAST A SHORT PERIOD OF SUNSHINE. THE FINAL LOW LIGHT VISIBLE SATELLITE IMAGE DID SHOW LOW CLOUDS BEGINNING TO IMPACT THE HALFMOON BAY AREA AS A DRY COLD FRONT APPROACHES THE COAST. THE GOES-E MVFR PROBABILITY IMAGE IS SHOWING LOW CLOUDS AHEAD OF THE FRONT WHICH WILL PUSH THE CLOUDS BACK OVER THE COAST AND INLAND VALLEY AREAS OVERNIGHT. THE 1800Z GFS40 AND 1200Z ECMWF HAVE INITIALIZED WELL WITH THE CURRENT SYNOPTIC WEATHER PATTERN AND REMAIN IN GOOD AGREEMENT THROUGH AT LEAST THURSDAY. BOTH MODELS BEGIN TO BUILD A RIDGE OF HIGH PRESSURE OVER THE FORECAST AREA TUESDAY MORNING. THE RIDGE IS EXPECTED TO BUILD TO 585DM BY WEDNESDAY. AT THE SURFACE LIGHT OFFSHORE WINDS ARE EXPECTED TO DEVELOP AS A THERMAL TROUGH BUILDS OVER CALIFORNIA. THE LIGHT OFFSHORE SURFACE WINDS COMBINED WITH THE STRONG RIDGE OF HIGH PRESSURE WILL ALLOW 850MB TEMPERATURES TO REACH 17 TO 19 DEGREES CELSIUS OVER THE FORECAST AREA ON WEDNESDAY WHICH TRANSLATES INTO WIDE SPREAD 80S ALONG THE COAST AND EVEN 90S FOR THE INLAND AREAS. THE MID WEEK HOT TEMPERATURES WILL NOT STICK AROUND LONG WITH COOLER TEMPERATURES EXPECTED THURSDAY AS SURFACE WINDS BECOME ONSHORE AHEAD OF AN APPROACHING LOW PRESSURE SYSTEM. THIS LOW PRESSURE SYSTEM IS EXPECTED TO IMPACT THE FORECAST AREA THE SECOND HALF OF THE WEEK WITH MUCH COOLER TEMPERATURES AND A POSSIBILITY OF RAIN THROUGH THE WEEKEND. && .AVIATION...AS OF 4:45 PM PDT SUNDAY...STRATUS HAS MIXED OUT FROM THE COAST THIS AFTERNOON BUT APPROACHING TROUGH HAS INCREASED THE ONSHORE FLOW AND STRATUS COULD QUICKLY SPREAD BACK IN. CONDITIONS FAVORABLE FOR EARLY RETURN OF STRATUS INTO THE SFO BAY AREA AT AROUND 04Z. CONFIDENCE IS NOT HIGH AS IT COULD COME IN LATER. VICINITY OF KSFO...MVFR CIGS AFTER 04Z. WEST WINDS SUSTAINED 15-20 KNOTS THROUGH 04Z. SFO BRIDGE APPROACH...SIMILAR TO KSFO. MONTEREY BAY TERMINALS...MVFR CIGS AFTER 02Z AT MRY AND 04Z AT SNS. && .BEACHES...AS OF 3:00 PM PDT SUNDAY...A LOW AMPLITUDE MODERATE TO HIGH ENERGY MIXED SWELL WILL CONTINUE TO MOVE THROUGH THE WATERS. THESE ENERGETIC WAVES WILL SUPPORT STRONG RIP CURRENTS AT LOCAL BEACHES WITH THE POTENTIAL FOR LARGE SHORE BREAK AT SOME BEACHES SUCH AS TWIN LAKES BEACH IN SANTA CRUZ. MIXED SWELL WILL SLOWLY SUBSIDE BY THIS EVENING. && .MARINE...AS OF 2:23 PM PDT SUNDAY...HIGH PRESSURE BUILDING OVER THE EASTERN PACIFIC EARLY IN THE WEEK WILL RESULT IN STRONGER NORTHWESTERLY WINDS AND SEAS ACROSS THE COASTAL WATERS. WINDS AND SEAS WILL EASE MIDWEEK AS THE GRADIENT DECREASES ACROSS THE REGION AS THE HIGH MOVES EAST. BY LATE IN THE WEEK A LOW PRESSURE SYSTEM WILL APPROACH THE REGION WITH A WET PATTERN EXPECTED BY NEXT WEEKEND. && .MTR WATCHES/WARNINGS/ADVISORIES... .TNGT...SCA...PT PINOS TO PT PIEDRAS BLANCAS 0-10 NM FROM 3 AM SCA...PT ARENA TO PIGEON PT 10-60 NM FROM 3 AM SCA...SF BAY UNTIL 9 PM && $$ PUBLIC FORECAST: LARRY AVIATION: W PI MARINE: CW VISIT US AT WWW.WEATHER.GOV/SANFRANCISCO FOLLOW US ON FACEBOOK AND TWITTER AT: WWW.FACEBOOK.COM/NWSBAYAREA WWW.TWITTER.COM/NWSBAYAREA  FXUS66 KMTR 020401 AFDMTR AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE SAN FRANCISCO BAY AREA 901 PM PDT SUN MAY 1 2016 .SYNOPSIS....COASTAL LOW CLOUDS AND FOG WILL CONTINUE TO PUSH NORTH IMPACTING THE COAST AND INLAND VALLEYS TONIGHT INTO MONDAY MORNING. DRY AND SEASONABLE WEATHER IS FORECAST THROUGH TUESDAY. A WEATHER SYSTEM WILL APPROACH CALIFORNIA BY THE MIDDLE OF THE WEEK...BRINGING A CHANCE OF SHOWERS BEGINNING WEDNESDAY LASTING INTO THE WEEKEND...ALONG WITH COOLER THAN NORMAL TEMPERATURES. && .DISCUSSION...AS OF 9:01 PM PDT SUNDAY...ACCORDING TO THE EXPERIMENTAL GOES R IFR PROBABILITY SATELLITE IMAGE LOW CLOUDS AND FOG ARE WORKING THEIR WAY UP THE BIG SUR AND SANTA CRUZ COAST AT THIS HOUR. HALF MOON BAY IS ALSO REPORTING REDUCED VISIBILITY AND LOW CLOUDS. THIS SOUTHERLY SURGE OF LOW CLOUDS AND FOG WILL CONTINUE NORTHWARD IMPACTING THE COAST AND INLAND VALLEYS OVERNIGHT INTO MONDAY MORNING. ACCORDING TO THE LATEST RUN OF THE HRRR FORECAST MODEL...LOW CLOUDS AND FOG SHOULD CLEAR OUT OF THE INLAND VALLEYS NOT LONG AFTER SUN RISE...BUT WILL REMAIN ALONG THE COAST THROUGH LATE MORNING. THE CURRENT SATELLITE WATER VAPOUR IMAGE IS SHOWING A TROUGH OF LOW PRESSURE CENTERED IN THE GULF OF ALASKA WITH A RIDGE OF HIGH PRESSURE CENTERED OVER THE SOUTHERN BORDER OF BRITISH COLUMBIA AND ALBERTA CANADA. THE 0000Z GFS40 AND 1200Z ECMWF HAVE INITIALIZED WELL WITH THESE FEATURES AND REMAIN IN GOOD AGREEMENT THROUGH AT LEAST NEXT SATURDAY. BOTH OF THESE MODELS SLIDE THE PREVIOUSLY MENTIONED TROUGH OF LOW PRESSURE SOUTH TOWARDS CALIFORNIA...BRINGING THE POTENTIAL FOR RAIN TO NORTHERN PORTIONS OF THE FORECAST AREA TUESDAY NIGHT SPREADING SOUTH WEDNESDAY. INSTABILITY ASSOCIATED WITH THE COOL UPPER LEVEL AIR OF THIS TROUGH OF LOW PRESSURE COULD SUPPORT A FEW ISOLATED THUNDERSTORMS WEDNESDAY AFTERNOON AND EVENING. THE THREAT OF SHOWERS AND ISOLATED THUNDERSTORMS WILL LINGER THROUGH THURSDAY. BY FRIDAY THE LOW PRESSURE SYSTEM WILL BE ENTERING ARIZONA...PLACING THE FORECAST AREA IN A GOOD POSITION FOR WRAP AROUND SHOWERS INTO THE WEEKEND. THE CURRENT FORECAST PACKAGE DOES A REASONABLE JOB WITH THE EXPECTED WEATHER CONDITIONS SO NO UPDATES ARE NEEDED AT THIS TIME. && .AVIATION...AS OF 10:30 AM PDT SUNDAY...DRY OFFSHORE FLOW KEEPING VFR TODAY. THE ONE FLY IN THE OINTMENT IN THE FORECAST IS A POSSIBLE SOUTHERLY SURGE LATER TODAY. LATEST NAM AND WRF SHOW A SOUTHERLY SURGE IMPACTING KMRY/KSNS...POSS MAKING IT INTO SF BAY OVERNIGHT. CONF IS MARGINAL. VICINITY OF KSFO...VFR. SFO BRIDGE APPROACH...SIMILAR TO KSFO. MONTEREY BAY TERMINALS...VFR BECOMING MVFR LATE THIS EVENING AND OVERNIGHT. && .MARINE...AS OF 01:22 PM PDT SUNDAY...HIGH PRESSURE OVER THE EASTERN PACIFIC WILL KEEP NORTHERLY WINDS OVER THE COASTAL WATERS TODAY. LOCALLY GUSTY WINDS WILL BE POSSIBLE OVER THE OUTER WATERS NORTH OF POINT REYES. SOUTHERLY WINDS WILL DEVELOP LATE TONIGHT AND EARLY MONDAY. A MODERATE SWELL WILL MIX WITH A SMALLER LONG PERIOD SOUTHERLY SWELL THIS WEEK. && .MTR WATCHES/WARNINGS/ADVISORIES... .TDAY...NONE. $$ PUBLIC FORECAST: LARRY AVIATION: SIMS MARINE: SIMS VISIT US AT WWW.WEATHER.GOV/SANFRANCISCO FOLLOW US ON FACEBOOK AND TWITTER AT: WWW.FACEBOOK.COM/NWSBAYAREA WWW.TWITTER.COM/NWSBAYAREA  FXUS66 KMTR 131623 AFDMTR Area Forecast Discussion National Weather Service San Francisco Bay Area 923 AM PDT FRI MAY 13 2016 .Synopsis... A low pressure system will begin to influence the region today... leading to cooler temperatures and a slight chance of rain over the North Bay on Saturday. Drier weather conditions and a slight warming trend is then expected for next week as high pressure builds over the region. && .Discussion...as of 09:15 AM PDT Friday... Today is Friday the 13th and another May gray day is upon us. The persistent marine layer that has inundated inland coastal regions over the last few mornings is evident again this morning on satellite imagery, especially around the Monterey Bay region. That said, satellite imagery is signaling that the marine layer is not nearly as robust as it has been over the last few days. These signals include a) higher cloud bases, which are generally 500-900 feet higher than the last two mornings and are approaching the top of the marine layer itself. b) The Fort Ord Profiler tops the marine deck just above 2000 feet and bases are already pushing 1700-1800 feet in the Bay Area, which indicates a much shallower layer there than previous mornings. c) The GOES-R proving grounds cloud thickness product shows rather shallow cloud depths of 100-600 feet throughout most of the inland SF Bay Area as opposed to 1000+ feet. And d) satellite imagery shows a few holes in the previously uniform offshore deck. This change can largely be attributed to changes in the nearshore air mass and flow ahead of an approaching upper level trough. Trough interactions with the marine stratus deck are usually fairly tricky, however, expect to see an earlier stratus retreat in the San Francisco Bay Area versus the Monterey Bay region where the stratus deck could linger into the afternoon. This feature will begin to influence the regional weather today and increasingly so into the weekend as it treks eastward across the Pacific Northwest. Temperatures will struggle to warm today and are expected to end the day a few degrees cooler than yesterday... and a few to several degrees cooler than the daily normal. Coastal drizzle has been reported and can be expected along the coast through morning, especially around the Monterey Bay region where the stratus deck is thicker. A slight chance of rain showers also exists in the north bay as the upper low shifts onshore to the north late tonight into early tomorrow. High pressure builds back into the region early next week... leading to a general warming trend into midweek where temperatures are expected to run a few to several degrees above normal. .Previous discussion...AS OF 03:59 AM PDT Friday...A persistent marine layer around 2000 feet in depth continues to impact the region with low clouds spreading well inland this morning. With this, temperatures are holding steady in the 50s for most locations under the cloud cover. As with the past few days, clouds will slowly burn-off through late morning over inland locations. Meanwhile, many coastal areas will remain under cloud cover through much of the day. Temperatures inland are forecast to be slightly cooler compared to yesterday given an increased onshore flow and as the mid/upper level ridge shifts inland. A mid/upper level system remains on track to push inland over the Pacific Northwest on Saturday. The latest forecast models push this system inland to our north, yet show light precipitation moving over the northern coastal waters and into the North Bay region early Saturday morning. Given better consistency with the forecast models, have increased coverage of a slight chance of showers from the San Francisco Peninsula Coast northward into the North Bay. Further south, expecting the marine layer to deepen ahead of the approaching trough tonight into Saturday morning which should result in continued chances of coastal drizzle. Otherwise, most locations south of the Golden Gate will remain dry as this system passes inland. Temperatures will generally remain below seasonal averages inland through the weekend due to the proximity of the mid/upper level trough. Mid/upper level ridging will then build over the eastern Pacific early next week and result in a gradual warming trend and continued dry weather conditions. In addition, northwesterly winds along the coast will increase and likely help with mixing of the marine layer. As a result, cloud cover will likely be less extensive each morning, at least less of an inland intrusion. Temperatures will warm back above average by Tuesday and persist into Wednesday given a warmer, drier air mass aloft. The warm-up will be short lived overall as the medium range models project another mid/upper level ridge impacting the Pacific Northwest late next week. && .Aviation...As of 4:46 AM PDT Thursday...Widespread stratus is moving in over the area on onshore winds. Clearing expected between 17z-19z across most terminals with the exception of the Monterey Bay terminals which may not clear until 20z-21z. Vicinity of KSFO...MVFR cigs then clearing anticipated around 18z today. Mainly light onshore winds except up to 15-20 kt 21z-04z. SFO Bridge Approach...Similar to KSFO. Monterey Bay Terminals...IFR cigs persist through this morning. Cigs anticipated to scatter out around 20z-21z today. Mainly light winds. IFR cigs return this evening. && .Marine...as of 08:09 AM PDT Friday...A weak gradient over the coastal waters will maintain light winds and seas through saturday. gusty winds are possible over the san francisco bay waters north of the bay bridge this afternoon and evening. winds increase late in the weekend into early next week as a low pressure system moves across the area. northwesterly swell will be mixed with a small long period southerly swell. && .MTR Watches/Warnings/Advisories... .Tday...SCA...SF BAY FROM 1 PM && $$ Public Forecast: DRP Aviation: Canepa Marine: Canepa Visit us at www.weather.gov/sanfrancisco Follow us on Facebook and twitter at: www.Facebook.com/nwsbayarea www.twitter.com/nwsbayarea  FXUS66 KMTR 151145 AFDMTR Area Forecast Discussion National Weather Service San Francisco Bay Area 445 AM PDT FRI JUL 15 2016 .SYNOPSIS...A weakening ridge of high pressure over Southern and Central California will result in another warm day inland. Coastal influences and onshore flow will keep temperatures seasonably cooler near the ocean and bays. Cooler temperatures are expected by Saturday as an upper level trough develops off the West Coast. && .DISCUSSION...as of 3:08 AM PDT Friday...Satellite imagery shows more extensive coastal stratus this morning, as compared to yesterday at this time, with low clouds extending into the San Francisco Bay and North Bay Valleys, and through the Monterey Bay and well into the Salinas Valley. Current temperatures are cooler than those from 24 hours ago with mid 50s to lower 60s most places. The onshore flow is also slightly stronger with 2.6 mb between SFO and SAC versus 1.8 mb yesterday at this time. High pressure aloft centered over the Desert Southwest is still extending into Southern and Central California, and will give one more day of very warm temperatures to inland areas in the district today. Highs today are expected to be slightly cooler than yesterday, though, with inland areas ranging from the lower 80s to near 100. By Saturday and upper level trough is progged to approach the West Coast. This will usher in a cooling trend that should last into early next week, with high temps perhaps 10 degrees cooler across inland areas. A gradual re-warming is expected by late next week as high pressure rebuilds into California from the east. && .AVIATION...As of 4:45 AM PDT Friday...The marine layer is much deeper this morning topping out at approximately 1500 feet. According to the GOES IFR probability product cigs are present in San Francisco Bay with a hole around SFO terminal. Cigs will pass over the terminal intermittently this morning. Low cigs and fog are impacting the Monterey terminals with stratus pushing well into the Salinas valley. Vicinity of KSFO...For the most part expect VFR at the terminal with periods of bkn-ovc005 passing over the terminals between 1200 and 1600Z this morning. VFR is expected from 1700Z on. The sea breeze will reach 18 kt this afternoon. Confidence is moderate. SFO Bridge Approach...Sct-Bkn008 are expected to pass over the approach this morning. First guess of morning burnoff around 1700Z. Confidence low to moderate. Monterey Bay Terminals...LIFR cigs ovc002-004 are expected to prevail this morning. First guess of morning burnoff at KMRY will be 1800Z and 1600Z at KSNS. The sea breeze is expected to reach 10 to 15 kt this afternoon. Confidence is moderate. && .MARINE...as of 2:52 AM PDT Friday...A thermal trough will remain positioned along the California coast for at least the next couple of days, maintaining generally light winds and seas over a majority of the coastal waters with stronger winds and rough seas expected over the northern outer coastal waters. Winds are anticipated to increase beginning Sunday as the thermal trough slides to the east. && .MTR WATCHES/WARNINGS/ADVISORIES... .Tday...SCA...Pt Arena to Pigeon Pt 10-60 nm SCA...SF Bay from 2 PM && $$ PUBLIC FORECAST: Sims AVIATION: Larry MARINE: Larry Visit us at www.weather.gov/sanfrancisco Follow us on Facebook and twitter at: www.Facebook.com/nwsbayarea www.twitter.com/nwsbayarea  FXUS66 KMTR 171201 AFDMTR Area Forecast Discussion National Weather Service San Francisco Bay Area 501 AM PDT SUN JUL 17 2016 .SYNOPSIS...The cooling trend that began on Friday will continue today and cooler than normal temperatures are expected to persist through Tuesday. A gradual warming trend is then forecast to begin around the middle of the week. && .DISCUSSION...As of 2:45 AM PDT Sunday...Early morning water vapor satellite imagery shows a longwave trough centered along the West Coast. A shortwave trough dropping south off the coast of the Pacific Northwest will act to deepen the longwave trough a bit over northern California the next few days and continue cool the airmass aloft. Meanwhile...the marine layer depth remains at about 2000 feet and moderate onshore flow persists. Thus...we can expect continued widespread night and morning low clouds over the next few days, along with cooler daytime temperatures inland. In fact, high temperatures across most inland areas are forecast to remain cooler than normal through Tuesday, and be as much as 10 degrees below normal. Temperature trends are expected to reverse course by the middle of the week. By midweek an upper ridge is forecast to strengthen over the country's midsection and expand west across California. This will lead to a gradual warming trend during the second half of the work week and into next weekend. Most warming is expected to occur inland, while coastal areas remain seasonably cool. Temperatures in most areas are expected to return to near normal by the end of the week, and perhaps climb a bit above normal next weekend. Otherwise, no significant weather is forecast over the next 7 days. && .AVIATION...As of 5:00 AM PDT Sunday...The current satellite fog product is showing stratus along the coast and well into the inland valleys this morning. According to the Fort Ord profiler the marine layer remains at a depth of 2000 feet, similar to yesterday. The GOES IFR probability product is showing a hole in the stratus around KSFO and a majority of the approach, however there is still time for this to fill in. A trough of low pressure is approaching from the northwest and may result in an early return of stratus this evening. Vicinity of KSFO...VFR is expected to prevail today with a potential for bkn-OVC015 to pass over the terminals between 1300 and 1500Z. The sea breeze will reach 15 to 20 kt this afternoon with gusts to 25 kt possible. Stratus will return to the bay early this evening potentially impacting the terminals by 0400z. Overall confidence is moderate. Confidence is low on early stratus return. SFO Bridge Approach...Stratus is present over the bay this morning and cigs BKN-OVC015 may fill in this morning, if it does the first guess on burn off is 1700Z. Stratus is also anticipated to fill in over the bay early this evening as a trough of low pressure continues to push towards the area. Confidence is low. Monterey Bay Terminals...Low clouds are well entrenched into the Monterey and Salinas area. First guess at morning burn off for KMRY is 1830 with KSNS burning off by 1900Z. Winds are expected to 15 kt this afternoon with gusts to 20 kt possible. Stratus is expected to return early this evening. Confidence is moderate. && .MARINE...as of 9:41 PM PDT Saturday...Gusty northwest winds will continue over the northern and outer waters overnight into Sunday. Elsewhere over the coastal waters winds will gradually increase Sunday. Gusty onshore winds are forecast north of the Bay Bridge Sunday afternoon and evening. Swells will be light through the weekend and into next week with fresh wind waves being the dominant wave energy over the inner waters. && .MTR WATCHES/WARNINGS/ADVISORIES... .Tday...SCA...Pigeon Pt to Pt Pinos 0-10 nm from 3 PM SCA...Pt Arena to Pt Reyes 0-10 nm SCA...Pt Reyes to Pigeon Pt 0-10 nm SCA...Pt Arena to Pigeon Pt 10-60 nm SCA...Pigeon Pt to Pt Piedras Blancas 10-60 nm SCA...Pt Pinos to Pt Piedras Blancas 0-10 nm from 3 PM SCA...SF Bay from 2 PM && $$ PUBLIC FORECAST: Dykema AVIATION: Larry MARINE: Canepa Visit us at www.weather.gov/sanfrancisco Follow us on Facebook and twitter at: www.Facebook.com/nwsbayarea www.twitter.com/nwsbayarea  FXUS66 KMTR 181748 AFDMTR Area Forecast Discussion National Weather Service San Francisco Bay Area 1048 AM PDT MON JUL 18 2016 .SYNOPSIS...Cooler than normal temperatures along with overnight clouds and patchy fog are expected to persist through Tuesday. A gradual warming trend is then forecast for the second half of the work week. Much warmer temperatures are possible by the upcoming weekend. && .DISCUSSION...as of 09:16 AM PDT Monday...Based on profiler data across the region, the marine layer remains around 2000 feet in depth this morning. This allowed for the typical inland intrusion of coastal clouds well into the valleys overnight. In addition, drizzle is being reported along the coast and into the East Bay as a result of the deep marine layer. Meanwhile, low clouds are burning-off over the South Bay and Santa Clara Valleys at this hour and will likely see this trend continue through the morning across inland areas. While clouds retreat to the coast, some locations near the coast may not break out from the cloud cover today or if so, only briefly. The ongoing forecast remains on track for today and no major changes are needed at this time. Overall, expecting similar weather conditions and temperatures to those on Sunday. && .PREV DISCUSSION...As of 3:00 AM PDT Monday...Little change is expected in our weather over the next couple of days as an upper trough remains in place along the West Coast. A deep marine layer and moderate onshore flow will continue to result in widespread night and morning low clouds, and temperatures will remain cooler than normal. An upper ridge centered over the nation's midsection is forecast to expand to the west during the second half of the week, which will result in a warming trend starting on Wednesday. The warming trend will start off slow with only a few degrees of warming expected through Thursday. The longer range models agree that the ridge will build much more strongly over California from Friday into the weekend and this is when the warming trend is expected to quickly ramp up. By midday Sunday the GFS forecasts a 597 dm 500 mb high centered over the Bay Area while the ECMWF forecasts a 599 dm high centered in the same location. If the ridge develops as forecast, we will see inland temperatures soar well into the 90s, and over 100 in the warmest locations, during the upcoming weekend. The bias-corrected high temperature forecast grids look to be about 10 degrees too cool during the Friday-Sunday time period and have therefore adjusted them upward for days 5-7. If the medium range models verify in the extended forecast period, Saturday and Sunday will probably be among the warmest days we've seen so far this summer, and almost certainly the warmest of July. && .AVIATION...As of 10:50 AM PDT Monday...For 18z tafs. Marine layer exhibiting typical clearing from all sides this morning... except over the San Francisco peninsula and East Bay. Advection of upstream air mass is contributing to a thicker layer of stratus directly over KSFO with KOAK on the fringe. Given current depth of the layer... the upstream marine air mass advection... and rate of mixing (per GOES cloud thickness product)... expect to see MVFR cigs linger through at least 19Z and as late as 20Z. Onshore winds then become breezy and occasionally gusty into the afternoon and early evening. MVFR cigs return this evening with IFR overnight. Vicinity of KSFO...MVFR into the 19Z hour. Sustained winds up to 20kt after 21Z with gusts to around 25 kt. MVFR returns by 04z TUE. IFR overnight. Confidence moderate. SFO Bridge Approach... Advection of marine stratus over SF peninsula will push into the South Bay... leading to similar albeit slightly improved conditions versus KSFO. Confidence moderate. Monterey Bay Terminals...MVFR cigs will linger through the 18Z hour. Upstream wind field does not currently appear favorable for cigs to linger into the early afternoon but a slight shift in the offshore winds may change this. Early return of low cigs by around 01-02Z TUE. Confidence moderate. && .MARINE...as of 09:16 AM PDT Monday...Northwest winds will be the strongest along the coast today...especially southward towards the Big Sur region. In addition look for gusty west winds this afternoon and evening across the northern San Francisco Bay as well as the outer waters of Monterey Bay. The gradient will gradually ease and expect generally light wind and seas from mid to late week as strong high pressure builds from the interior and keeps gradients light across the waters. && .MTR WATCHES/WARNINGS/ADVISORIES... .Tday...SCA...Pigeon Pt to Pt Pinos 0-10 nm from 1 PM SCA...SF Bay from 1 PM SCA...Mry Bay from 1 PM SCA...Pt Pinos to Pt Piedras Blancas 0-10 nm && $$ PUBLIC FORECAST: RGass AVIATION: DRP MARINE: DRP Visit us at www.weather.gov/sanfrancisco Follow us on Facebook and twitter at: www.Facebook.com/nwsbayarea www.twitter.com/nwsbayarea  FXUS66 KMTR 021645 AFDMTR Area Forecast Discussion National Weather Service San Francisco Bay Area 945 AM PDT FRI SEP 2 2016 .SYNOPSIS...A slight cooling trend is forecast for the upcoming weekend with the possibility of overnight and morning coastal drizzle. Temperatures will trend warmer for next week with ongoing dry weather conditions. && .DISCUSSION...as of 09:45 AM PDT Friday... Water vapor imagery shows a distinct upper level trough centered over the Pacific Northwest and pushing into northern California this morning. Mixing associated with this advancing feature has entrained drier air into the marine layer and weakened its presence north of the Monterey Bay region. Breezy northwest winds have advected lingering marine stratus into the Monterey Bay which, due to the windfield, has wrapped around the the southern/eastern lip of the Bay in a counterclockwise trajectory. GOES cloud thickness product indicates a 2500 foot marine stratus deck thickness directly over Moss Landing. Otherwise, most other communities are experiencing mostly sunny to clear skies this morning as the upper trough shifts closer to home. The aforementioned 558DM upper low is being accompanied by an advancing air mass boundary and a 1.00" precipitable water plume. A band of high level clouds have developed along these features and will move southward across the region through the day. Forecast models are generally shying away from generating precipitation from this feature. The NAM, which is generally far too optimistic when it comes to precipitation here, is indicating that some light rain may be possible along the coast. Odds favor that only a trace to a few hundredths of drizzle along the coast should be even been considered. Additionally, breezy northwest winds should accompany the low as it shifts across the state through the weekend. The slow moving trough will exit the region early next week and be replaced by gradually building high pressure from the eastern Pacific. This will lead to a general warming and drying trend, but that said, temperatures will generally remain below normal for all of next week. Only a few locations located deep inland will see temperatures rise to a few degrees above normal. Of interest later next week... the EURO model shows a tropical system moving north along the Baja California coastline before entering into southern California by late Thursday/early Friday. The EURO shows this tropical system rapidly disorganizing as it moves inland, but allows the remnant tropical energy/moisture to linger there through next weekend. Meanwhile, the GFS kicks the feature west into the Pacific. This feature could play a key role in the weather for our southern counties next weekend and should be watched closely. .PREVIOUS DISCUSSION...as of 03:32 AM PDT Friday...Drier air mixing into the boundary layer has resulted in a less defined marine layer over the region this morning. As a result, only seeing patchy low clouds around portions of the Monterey Bay Region, down into the Salinas Valley and around portions of the North Bay. Along with this, temperatures are generally in the 50s to lower 60s region- wide. With this pattern over the region, should see earlier clearing of low clouds that do develop through sunrise. Thus, mostly sunny conditions are forecast for inland areas this afternoon and early evening. Meanwhile, temperatures this afternoon are forecast to be similar to those yesterday. A slight cooling trend is then forecast for the upcoming weekend as a short-wave trough drops southward down the West Coast. As this feature approaches, expect a slight deepening of the marine layer that will likely result in patchy coastal drizzle during the late night and early morning hours through the weekend. In addition, northwesterly winds are forecast to increase and become breezy at times from Friday into Saturday evening. The forecast models generally agree on shifting the broad mid/upper level trough inland as high pressure builds over the eastern Pacific early next week. This will bring a slight warming trend back to the region with temperatures rebounding back to near seasonal averages. The presence of a marine layer will likely bring minor day to day changes in coverage of overnight and morning low clouds. Otherwise, expect dry weather conditions and temperatures typical for early September through the extended forecast period. && .AVIATION...as of 5:05 AM PDT Friday....Thanks to a northerly gradient currently greater than 5 MB (with a westerly piece under 2 MB) and a marine layer just over 1,000 feet clouds have been limited for most of the SF Bay Area. Generally expect VFR conditions in most spots north of Monterey Bay outside of KOAK where clouds in the eastern part of SF Bay will bring CIGs down to MVFR at times. Moderate to high confidence. Vicinity of KSFO..VFR through the day with sea breeze westerly winds after 21Z. Gusts could be over 25 KT by that time. MVFR CIGs forecast to return tonight. Moderate to high confidence. SFO Bridge Approach...Similar to KSFO. Monterey Bay Terminals..IFR cigs until around 18Z. Patchy drizzle possible early Friday morning. VFR expected remainder of the day. && .MARINE...as of 09:21 AM PDT Friday...Look for moderate northwesterly winds to continue through the weekend. The strongest winds are expected along the Sonoma coast north of Point Reyes as well as around Point Sur on the Big Sur coast. The primary swell will remain northwesterly and generally be 4 feet at 8 seconds. && .MTR WATCHES/WARNINGS/ADVISORIES... .Tday...SCA...Mry Bay from 2 PM SCA...Pigeon Pt to Pt Pinos 0-10 nm from 2 PM SCA...Pt Arena to Pt Reyes 0-10 nm SCA...Pt Reyes to Pigeon Pt 0-10 nm SCA...Pt Arena to Pigeon Pt 10-60 nm SCA...Pigeon Pt to Pt Piedras Blancas 10-60 nm SCA...Pt Pinos to Pt Piedras Blancas 0-10 nm && $$ PUBLIC FORECAST: DRP AVIATION: Bell MARINE: BAM Visit us at www.weather.gov/sanfrancisco Follow us on Facebook and twitter at: www.Facebook.com/nwsbayarea www.twitter.com/nwsbayarea  FXUS66 KMTR 151146 AFDMTR Area Forecast Discussion National Weather Service San Francisco Bay Area 346 AM PST Sun Jan 15 2017 ...Wet and windy weather returns starting the middle of the week... .SYNOPSIS...Dry weather conditions and seasonable temperatures will persist across the region through Tuesday. An active weather pattern will then develop by the middle part of the week and will potentially persist into next weekend as a series of storm systems move through California. Moderate to heavy rainfall is likely at times, as well as locally strong and gusty winds. && .DISCUSSION...As of 3:30 AM PST Sunday...A weak weather system offshore is moving south parallel to the coast early this morning. Radar shows weak returns well offshore. Based on latest model data, any light precipitation is expected to remain offshore this morning and move well to our south by this afternoon. Areas of fog have developed early this morning, mainly in the East Bay near the Delta as well as the North Bay Valleys. Patchy dense fog is likely in these areas until mid morning. In addition, patchy low clouds have developed near the coast and near San Francisco Bay. Expect most low clouds and fog to clear by midday. Once the weak system offshore moves off to the south later today, a shortwave ridge is forecast to build across California. This ridge will maintain dry and mild weather across our region through Tuesday. Patchy night and morning dense fog will continue, especially in the North Bay Valleys and near the Delta. The models remain consistent in forecasting a return to an active weather pattern by midweek, with potentially three storm systems set to track across California from Wednesday through early next week. The GFS and ECMWF are in reasonably good agreement regarding the first two systems. The first system will direct a plume of moist air into the Pacific Northwest beginning late Monday. The frontal boundary and moisture plume will remain well to our north through Tuesday and then finally push south into northern California by late Tuesday night and Wednesday as a robust shortwave trough approaches from the WNW. Expect widespread rain to spread across our area from late Wednesday morning through Wednesday evening. After a break in the action from late Wednesday night through Thursday evening, the second system will sweep in from the WNW and produce another round of widespread rainfall late Thursday night and Friday. Both of these systems will have a fair amount of moisture at their disposal and be dynamic enough to produce moderate to heavy rainfall. However, they are both expected to move through our area relatively quickly and so overall rainfall accumulation is not expected to be excessive. Rainfall totals by late Friday (from the first two systems combined) are expected to range from 1 to 2 inches at lower elevations and in urban areas (except locally less in some inland valleys) and from 2 to 4 inches in the coastal hills. Normally rainfall of this magnitude over three days would not result in significant hydro issues. However, given that soils remain saturated from heavy rains over the past two weeks, even short- duration intense rainfall could result in at least minor flooding issues as well as mud and rock slides in areas of steep terrain. In addition, both systems will likely produce locally strong and gusty winds near the coast and in the hills. Winds are not expected to be as strong as what occurred last week, but gusts up to 50 mph are certainly possible for a few hours in advance of frontal passage on Wednesday and again on Friday. Beyond Friday the models continue an active weather pattern but differ on the specifics. Periods of rain will likely continue through next weekend, with one more strong storm system due to impact our region sometime between Sunday night and Monday evening. Both the GFS and ECMWF indicate this third system may be the wettest and windiest of the three. However, this is still a week out and consequently there is uncertainty regarding timing and potential impacts. && .AVIATION...As of 3:45 AM PST Sunday...The challenge for this morning is whether SFO and OAK will be impacted by the low clouds over the water or the dense fog reported at CCR and SUU. The regular satellite image is covered by by high clouds but the GOES-W LIFR Probability Image shows IFR and LIFR in the 30-50% range spreading into the northern part of SFO Bay. It is more likely that the low clouds from the ocean will have a greater impact on SFO and OAK than the fog as winds are very light this morning. Tomorrow morning may be more of a challange as the offshore flow will strengthen a bit which may push more of the fog into the SFO Bay Area. This is supported by the NAM which forecasts high RH right near the surface. Vicinity of KSFO....Possible IFR conditions 13Z through 17Z. Light winds. SFO Bridge Approach...Same as KSFO. Monterey Bay Terminals...VFR. && .MARINE...as of 3:45 AM PST Sunday...High pressure off the coast will keep light northwest winds through Tuesday except along the Big Sur coast where a coastal jet will maintain gusty winds south of Point Sur through tonight. A storm system will bring increasing southerly winds on Wednesday. Large swells are forecast to arrive by Thursday with very large swells by the weekend. && .MTR WATCHES/WARNINGS/ADVISORIES... .Tday...SCA...Pt Pinos to Pt Piedras Blancas 0-10 nm && $$ PUBLIC FORECAST: Dykema AVIATION: W Pi MARINE: W Pi Visit us at www.weather.gov/sanfrancisco Follow us on Facebook and twitter at: www.Facebook.com/nwsbayarea www.twitter.com/nwsbayarea  FXUS66 KMTR 221154 AFDMTR Area Forecast Discussion National Weather Service San Francisco Bay Area 454 AM PDT Sat Apr 22 2017 .SYNOPSIS...An approaching upper level trough will bring cooler weather to the district today along with increasing clouds. Unsettled weather is expected through much of next week with passing showers mainly across the north. && .DISCUSSION...as of 2:30 AM PDT Saturday...Mild temperatures across the area this morning with readings ranging from the upper 40s to upper 50s. These temperatures are generally 1-4 degrees warmer than those 24 hours ago. Today is expected to be a little cooler than Friday across the region, with clouds increasing as an upper level trough approaches the area. Rain chances are expected to remain to the north of the district, but some light drizzle is possible near the coast and in the north by this evening. Clouds will decrease on Sunday but northwest winds will ramp up and cooler temperatures are expected. We could see 5-10 degrees of cooling by Sunday with highs only in the upper 50s to near 70. Mainly zonal flow aloft will dominate the pattern next week keeping temperatures on the cool side as weak impulses brush across the northern part of the state. The best chances for rain in our area are late Monday through early Wednesday, but even then, the best chances will be from the Bay Area northward. Rainfall amounts will be light. High temperatures are expected to stay in the 60s to mid 70s through the week. High pressure to rebuild along the west coast by week's end. && .AVIATION...as of 4:35 AM PDT Saturday...For 12z Tafs. A weak cold front will pass through the area later this morning. No precip expected, but if any precip does occur, it will be in the form of -DZ. Confidence not high enough to include in tafs. Questions remain whether there will be a few hours of low cigs as the cold front passes. Decided to include MVFR cigs for North Bay and SF Bay terminals between 18-21z, as satellite imagery has been consistent showing high MVFR probabilities along the cold front. However, confidence is low with timing and cig heights. BKN high clouds will dominate the afternoon and evening hours. W/NW winds become gusty this afternoon, gusts 20-25 kt for most terminals. Low cigs return tonight, around 03-04z. Overall forecast confidence: Medium. Vicinity of KSFO...Generally VFR. Could be a couple of hours of MVFR cigs, around 2000 ft, with FROPA. Breezy west winds this afternoon, gusts to 25 kt possible. Low cigs by 03-04z, but low confidence on timing and cig heights. SFO Bridge Approach...Similar to KSFO. Monterey Bay Terminals...VFR. FROPA may bring in BKN MVFR cigs, but low confidence to include in tafs. Gusty onshore winds this afternoon. Sustained winds 10-12 kt, with gusts in excess of 15 kt. Low cigs possible tonight. && .MARINE...as of 2:20 AM PDT Saturday...A dry cold front will approach from the northwest and move through the coastal waters this morning. Northwest winds are expected to remain light to moderate through the day for all zones except the southern coastal waters zones from Point Pinos to Point Piedras Blancas. Thermal troughing along the southern California coast will aid in increasing winds over the southern coastal waters today. This trough is expected to build northward by Sunday and increase winds along the coastline of central California. Northwest to west swell will build this evening and into the early part of next week. && .MTR WATCHES/WARNINGS/ADVISORIES... .Tday...SCA...Pt Pinos to Pt Piedras Blancas 0-10 nm && $$ PUBLIC FORECAST: Sims AVIATION: BAM MARINE: BAM Visit us at www.weather.gov/sanfrancisco Follow us on Facebook, twitter, and youtube at: www.Facebook.com/nwsbayarea www.twitter.com/nwsbayarea www.youtube.com/nwsbayarea  FXUS66 KMTR 240545 AFDMTR Area Forecast Discussion National Weather Service San Francisco Bay Area 1045 PM PDT Tue May 23 2017 .SYNOPSIS...An inland cooling trend will continue through late week as high pressure weakens and the marine influence increases. Minor warming is then expected during the upcoming weekend as high pressure returns to the West Coast. && .DISCUSSION...as of 08:20 PM PDT Tuesday...Only minor adjustments made to sky cover based on current trends. As of 7:50 pm PDT, visible satellite showed an extensive area of low clouds off the coast and impacting parts of the Bay Area with the clouds intruding through the Golden Gate east to Berkeley. Fort Ord profiler shows the marine layer around 1,500 ft this evening. Tuesday was another warm day for inland locations with highs ranging from the 80s to low 90s. Don't expect to see any 90s tomorrow as the ridge responsible for bringing the well above normal temperatures continues to push east into the continent. Most inland locations can expect to see temperatures about 5 to 10 degrees cooler on Wednesday. Additional cooling will occur from Wednesday to Thursday as an upper level low centered over southwestern Canada allows for 500 mb heights to continue to fall over the region. High temperatures by Thursday will fall to the upper 60s to mid 70s across the East Bay and South Bay, as well as the Salinas Valley. Coastal locations can expect widespread middle 50s to middle 60s with marine stratus. Models suggest another ridge to build over the West Coast in time for the holiday weekend, though at this point it doesn't look that it'll be as warm as it was over the past few days. Temperatures should be at or within several degrees of climatological normals for the end of May. && .PREV DISCUSSION...as of 01:32 PM PDT Tuesday...Low clouds continue to hug the coast this afternoon with mostly sunny skies inland. With this, the warmest temperatures persist over inland areas while cooler temperatures (generally in the upper 50s to lower 60s) are common at the coast. This trend will likely persist into tomorrow, with low clouds spreading inland this evening and into the overnight hours with a marine layer of around 1500 feet in place. However, as the ridge aloft weakens and onshore flow increases, inland locations will see the gradual cooling trend continue into Wednesday. With the deepening marine layer, cannot rule out patchy coastal drizzle/mist during the late night and early morning. However, measurable precipitation is highly unlikely. Further cooling is expected late in the week as the ridge flattens and an upper level low drops down into the northern Rockies. With this and an increase marine influence, looks for temperatures to fall below seasonal averages for just about all inland locations. More widespread 60s and 70s will be likely during the afternoon hours beginning on Thursday and continuing through Saturday. By late in the weekend and into early next week, a ridge of high pressure is currently forecast to rebuild over the West Coast. This would likely result in a slight warming trend with afternoon temperatures back to near seasonal averages. In addition, look for mostly sunny afternoon conditions inland while coastal clouds will be possible. && .AVIATION...As of 10:44 PM PDT Tuesday...A deepening marine layer will usher in increasing marine based stratus and fog this evening into Wednesday morning. IFR cigs will likely transition to MVFR cigs very late tonight into Wednesday morning, timing this is challenging. Higher surface pressures over the Central Coast and lower pressures over far northern California through Wednesday will add a southerly component to the wind probably influencing the marine layer cloud cover. Additionally, a lower level cyclonic circulation over the offshore waters approaches the coastal waters just west of the Bay Area Wednesday. Vicinity of KSFO...VFR, so far so good, is holding this evening. Held onto 10z IFR cig forecast for 06z taf issuance. IFR prob transitioning to MVFR cig early Wednesday morning, confidence is low. MVFR cig may hold on through the morning as there is plenty of stratus over the coastal waters combing with solid westerly flow which may become gusty Wednesday afternoon and evening. SFO Bridge Approach...Similar to KSFO. Monterey Bay Terminals...IFR cigs tonight possibly trending over to an MVFR early Wednesday morning, confidence in timing is low. Plenty of stratus over the coastal waters combined with onshore winds may keep MVFR cigs going through all of Wednesday morning. Low confidence VFR returns Wednesday afternoon. Stratus is likely to redevelop by early Wednesday evening. && .MARINE...as of 10:22 PM PDT Tuesday...Surface high pressure will be located over the Central Coast tonight through Wednesday resulting in mainly light west to southwesterly winds over much of the coastal waters with exception of the far northwestern coastal waters where winds will still be northerly. Winds are forecast to weaken late this week. && .MTR WATCHES/WARNINGS/ADVISORIES... .Tngt...SCA...Pt Arena to Pigeon Pt 10-60 nm && $$ PUBLIC FORECAST: Rowe/RGass AVIATION/MARINE: Canepa Visit us at www.weather.gov/sanfrancisco Follow us on Facebook, twitter, and youtube at: www.Facebook.com/nwsbayarea www.twitter.com/nwsbayarea www.youtube.com/nwsbayarea  FXUS66 KMTR 171150 AFDMTR Area Forecast Discussion National Weather Service San Francisco Bay Area 450 AM PDT Thu Aug 17 2017 .SYNOPSIS...A gradual inland warming trend can be expected through late week as high pressure builds over the region. Overnight and morning clouds will also be common, especially near the coast and in the adjacent valleys. && .DISCUSSION...as of 4:14 AM PDT Thursday...Skies are clear thus far over most of Napa county, parts of the East Bay and South Bay, San Benito and interior Monterey counties while stratus and fog blanket the bays and the rest of the coast early this morning. The marine layer depth is holding steady at 2,000 feet. The marine inversion is fairly well developed and further strengthening occurs today into Saturday as increasing subsidence in advance of a 594 decameter closed mid-upper level high centered approx 700 miles west of the Bay Area produces large scale sinking and adiabatic warming. Thermal ridging coincides with geopotential height ridging over NorCal today into at least the first part of the weekend, and per most recent NAM model output warming becomes focused over inland valleys and hills especially over the Bay Area counties, and in particular over the North Bay Friday and Saturday. 925 mb level temperatures reach 28C over North Bay tonight and then 30C Friday night meaning temperatures in the North Bay Hills and Mountains will most likely hover in the lower to middle 80s all night as the marine layer becomes increasingly squashed under high pressure. With this in mind, am not having a whole lot of confidence in daytime maximum temperature guidance especially for North Bay and East Bay areas Friday and Saturday; 90s to near 100 will probably be more common even closer to the bays as the marine layer becomes increasingly compressed. Eventually an active mid latitude zonal jet stream crossing the lower 48 buckles ever so slightly causing a weak and slowly SW moving upper level trough to form over the west coast and east Pacific by late this weekend into early next week. Model output has been consistent with showing lower to mid level thermal ridging weakening over the forecast area while this trough develops, however with a solidly strong position to start there'll still be remnants of it to persisting causing the marine layer to persist Sunday into Monday. At the same time much drier 925 mb RHs sweep in from the northwest over the weekend probably mixing into the marine based clouds with a tendency for lower level winds, and possibly surface winds to go from onshore to having a weak southerly component. The question is how will all of this influence the marine layer early next week? It's just a guess that there could be an earlier than usual clearing Monday morning. For mid-late next week, a very deep low pressure area develops over the Gulf of Alaska. The ECMWF, GFS, GEM have been lean toward weak long-wave troughing over the west coast. The southern extent of the Gulf of Alaska low arrives as a trough bringing more pronounced cooling and increasing onshore winds. Coastal drizzle is a possibility in a deepening or even possibly a fully mixed out marine layer. && .AVIATION...As of 4:50 AM PDT Thursday...Building east Pacific basin ridge continues to compress marine layer this morning. Fort Ord Profiler shows a top of approximately 1800 feet with a base around 800 feet, while the cloud thickness satellite imagery is estimated to be around 1000 feet. Latest GOESR nighttime microphysics imagery shows the stratus deck rapidly expanding across the San Francisco and Monterey Bay areas early this morning. Expect to see these clouds continue to thicken up and expand through dawn before quickly mixing out between 16-17Z. Marine layer will continue to compress tonight with slightly lower CIGS and less thickness overall. Light winds today, increasing tomorrow. Vicinity of KSFO...MVFR cigs through sunrise, then dissipating between 15-16Z. Light northerly morning winds shifting to become breezy and out of the west by the afternoon. SFO Bridge Approach...Similar to KSFO. Monterey Bay Terminals...MVFR cigs through 17-18Z. IFR cigs possible tonight beginning as early as 02-03Z. && .MARINE...as of 04:43 AM PDT Thursday...Light variable winds through the day as an east Pacific ridge builds inland to the north while a weak trough lingers just to the south. Expect increasing northwest winds beginning late tomorrow and lasting through the weekend as the ridge strengthens further. && .MTR WATCHES/WARNINGS/ADVISORIES... .Tday...SCA...SF Bay from 1 PM && $$ PUBLIC FORECAST: Canepa AVIATION: DRP MARINE: DRP Visit us at www.weather.gov/sanfrancisco Follow us on Facebook, twitter, and youtube at: www.Facebook.com/nwsbayarea www.twitter.com/nwsbayarea www.youtube.com/nwsbayarea  FXUS66 KMTR 020457 AFDMTR Area Forecast Discussion National Weather Service San Francisco Bay Area 957 PM PDT Wed Nov 1 2017 .SYNOPSIS...Clear to mostly clear skies this evening will give way to cloudy skies Thursday. A large scale weather pattern change is presently underway over the western contiguous United States. The last remnants of high pressure in the mid to upper levels over northern California will continue to break down and weaken tonight and Thursday. Initially, colder air pooling over the Gulf of Alaska will only sluggishly move southward over the eastern Pacific. Being an ill-defined cold front at first, by late week it'll become more solidly formed and arrive in the North Bay late Friday night into early Saturday morning. Even though this front will become better defined it'll still remain a slow moving front with it not clearing south of the Central Coast until late Saturday night. Light to moderate rain and breezy winds shifting to the west and northwest will accompany frontal passage. A break in precipitation is possible Saturday night into Sunday before a somewhat faster moving cold front from the Gulf of Alaska pushes through Sunday night into Monday morning. A colder, off and on wet pattern will continue well into next week. && .DISCUSSION...as of 9:57 PM PDT Wednesday...It's clear to mostly clear this evening with winds generally under 10 mph except a few very localized westerly gusts to 20 mph are reported in the North and East Bay mountains/hills. Patchy low clouds and possibly some fog combined can be seen over the northern coastal waters based on GOES/LIFR prob satellite imagery. 24 hour trends indicate temperatures are mainly neutral to 1 to 3 degrees cooler than this time last evening. The SFO-SAC pressure gradient is approx the same as it was last evening at 1 mb. Clear skies tonight will turn to cloudy skies Thursday as a moist and cooler flow develops. The large scale pattern is presently changing and remains the main focus through late week including next week as well. All things considered the models had at least initially handled this weather change with some consistency, but has since seen much more struggle with details due mostly to the incredibly complex upstream north- south split flow over the central Pacific. Generally speaking the tilt toward a colder, wetter pattern is still on track, the biggest problems have risen on the timing and extent of QPF for late week and this weekend as the models greatly struggle with timing downstream dynamics and thermodynamics of frontal and trough development over the eastern Pacific. This is often the case when there is split flow upstream. Colder air pooling over the Gulf of Alaska will eventually form into a better defined cold front, but it'll be slow moving and shallow sloped as the wind flow above the front nearly parallels it Friday night through Saturday night. Light to moderate rain and breezy winds shifting to the west and northwest will accompany frontal passage. The long lasting long wave ridge over the west continues to dissipate. Deeper and colder long wave troughing will become more prevalent over the west coast and eastern Pacific from late week and well into next week. With a little loss of confidence in the details in present model forecasts it still looks like with at least moderate confidence that a colder, off and on wetter pattern will develop late week and continue well into next week. && .PREV DISCUSSION...as of 01:50 PM PDT Wednesday...The much advertised pattern change is still the main focus through early next week. Afternoon synoptic analysis puts a weak upper level ridge along 40N nosing into the Bay Area. Generally sunny skies prevail this afternoon with lingering clouds along the North Bay Coast. The ridging aloft weakens overnight with lowering 500mb hts and dropping 850mb temps. Latest hi-res models indicate a return of low clouds overnight, but not a typical summertime stratus deck. The cooler temperatures noticed today will continue to trend cooler for Thursday. A more broad scale upper level trough will deepen off the Pac NW Coast Thursday into Friday and eventually drop south this weekend. As a result, warm sector/light precipitation will be possible Thursday afternoon/evening over the North Bay. Moisture and lift increase across the North Bay Friday and Friday night increasing rain chances. Southerly flow will increase ahead of an approaching cold front during the day Friday. Despite increasing rain chances on Friday/Friday night, rain shadowing will be possible across valleys due to the southerly flow. By early Saturday the cold front slowly moves southward toward Monterey/Big Sur shifting the focus of rainfall. In fact, the North Bay could see rain decrease early Saturday while southern areas see an increase. Latest model guidance actually brings a wave/weak low along the frontal boundary on Saturday. The wave/weak low has some decent moisture associated with it (PWATS >1 in) and keeps it mainly focused from the Santa Cruz Mountains southward. A brief break in the action is possible Saturday night into Sunday before another weak frontal boundary pushes south. The second boundary brings additional rainfall Sunday night into Monday. Very little changes from previous precip amounts. Storm total rainfall amounts 1.00" to 1.50" range in the coastal ranges and in the North Bay Mountains/Hills. Meanwhile, amounts of 0.25" to 0.75" are forecast near the coast and in the lower elevations with potentially much lower amounts in the rain shadowed valleys. Given recent fires much attention will be focused over the North Bay. Given latest model guidance and precip estimates debris flow potential appears to be marginal. Will be watching the situation closely. Longer range remains the same with drier conditions returning Monday into Tuesday. Rain chances return the middle of next week as another upper level trough swings through the region. && .AVIATION...As of 4:35 PM PDT Wednesday for 00Z TAFs. Currently VFR with westerly winds. Expecting patchy stratus to push inland tonight bringing MVFR cigs to some sites through the morning. Low to mid level moisture will then move in tomorrow ahead of the approaching system. This will bring SCT to BKN cigs generally around 2000-7000 ft before showers begin to arrive late tomorrow night. Vicinity of KSFO...VFR with westerly winds around 10 to 15 kt before winds decrease tonight. Low confidence on overnight conditions as marine layer tries to push inland and prefrontal moisture begins to advect in at 2-7K AGL. TAF carrying MVFR cigs 10-17Z tomorrow. SFO Bridge Approach...Similar to KSFO. Monterey Bay Terminals...VFR, light winds, clear skies this evening. Some low to mid level moisture advects ashore early tomorrow, with MVFR to VFR cigs that will hang around through the evening. && .MARINE...as of 02:43 PM PDT Wednesday...Light variable winds through midday Thursday. Winds will increase and become south to southwest ahead of an approaching front later later this week, before turning northerly behind the front early this weekend. These winds may produce locally steep fresh swell ahead of the front. Otherwise, generally light northwest seas. && .MTR WATCHES/WARNINGS/ADVISORIES... .Tngt...None. $$ PUBLIC FORECAST: Canepa/MM AVIATION: AS MARINE: DRP Visit us at www.weather.gov/sanfrancisco Follow us on Facebook, Twitter, and YouTube at: www.facebook.com/nwsbayarea www.twitter.com/nwsbayarea www.youtube.com/nwsbayarea  FXUS66 KMTR 070047 AFDMTR Area Forecast Discussion National Weather Service San Francisco Bay Area 547 PM PDT Sun May 6 2018 .SYNOPSIS...A weak system passing to our north will allow for seasonably cool conditions across much of the area this afternoon. Building high pressure will allow for a warming trend on Monday and Tuesday before cooler temperatures return on Wednesday. Another warming trend is expected late week and into next weekend. && .DISCUSSION...as of 12:55 PM PDT Sunday...This morning's low clouds along the coast quickly mixed out across much of the area by midday, revealing partly cloudy skies for this Sunday afternoon. Despite the sunshine, temperatures are generally running at or several degrees cooler than this time 24 hours ago. The cooler temperatures can be attributed to a shortwave passing through northern California that has aided in the decreased geopotential heights and 1000-500 mb thickness values. Today's shortwave will be replaced on Monday with a ridge just off the West Coast. Subsidence and warming of the mid/upper levels of the atmosphere will likely cause the marine layer to compress over the next 24 hours, which in turn may limit tomorrow morning's marine stratus inland intrusion. Consequences to the compression of the marine layer would be lower ceilings for those coastal areas that do see stratus, as well as the potential for coastal drizzle. Temperatures are expected to respond accordingly to the ridge with many locations forecast to warm by about 4 to 8 degrees for Monday afternoon with widespread 70s and 80s for interior locations. Similar conditions are expected on Tuesday as the ridge builds and axis moves east into the Intermountain West. The warming trend will cease on Wednesday as forecast models advertise an approaching trough. At this point, most if not all areas in the CWA should remain dry. Aside the cooler afternoon temperatures, this trough will likely lead to a deepening marine layer along the coast. By late week another ridge will build in the eastern Pacific and gradually approach the West Coast. Temperatures will climb as heights rise with more widespread 80s for interior locations. Wouldn't be surprised if some 90 degree readings return to locations such as Pinnacles National Park or southern Monterey County by next weekend. && .AVIATION...As of 5:47 PM PDT Sunday...VFR, greater than 6 miles visibility reported per metar observations and webcams back this up showing good visibilities as well. Thick cirrus clouds are streaming west to east associated with a jet streak and increasing upper level divergence; the ECMWF forecasts decreasing mid to upper level relative humidity late tonight and Monday, once the jet streak passes by cirrus clouds should thin out. Cirrus this evening, reducing outgoing nocturnal radiative cooling, may slow the development and limit the coverage of coastal stratus extending VFR at least into the evening. GOES-16 MVFR probability does show some marine layer stratus over the coastal waters while northerly and westerly pressure gradients, resulting in locally gusty W-NW winds, are both running approx 3 mb. The marine layer slopes from 1,300 feet Point Sur to 2,000-2,500 feet Bay Area based on profiler data. Some restoration of lower level thermal ridging occurred today, little change in strength is forecast tonight, then thermal ridging strengthens Monday and Monday night thus the marine layer should become more compressed Monday and Monday night. 00z tafs continue with VFR for the evening, it's a near high confidence forecast. 00z tafs with exception of tempo MVFR cig KOAK Monday morning continue with VFR tonight as well, but it's low to moderate confidence for late tonight and Monday morning. Vicinity of KSFO...VFR, westerly wind gusting to mid to upper 20 knot range til about 03z this evening. Westerly wind becoming similarly gusty again Monday by 21z. SFO Bridge Approach...Similar to KSFO. Monterey Bay Terminals...VFR, a few patches of stratus are possible by late evening and/or Monday morning. Winds becoming mainly light W-SW by mid evening, onshore winds becoming locally gusty Monday afternoon. && .MARINE...as of 4:44 PM PDT Sunday...Moderate northwesterly winds will persist through Monday with locally stronger winds off of the Sonoma and Santa Cruz County coastlines as well as off of the Big Sur coast during the afternoon and evening. Winds will diminish slightly Tuesday as high pressure builds over the eastern Pacific. Generally light northwest swells will continue with locally steeper fresh swell. && .MTR WATCHES/WARNINGS/ADVISORIES... .Tngt...SCA...Pt Arena to Pt Reyes 0-10 nm until 3 AM SCA...Pigeon Pt to Pt Pinos 0-10 nm until 3 AM SCA...Mry Bay until 12 AM SCA...Pt Pinos to Pt Piedras Blancas 0-10 nm && $$ PUBLIC FORECAST: Rowe AVIATION: Canepa MARINE: RGass Visit us at www.weather.gov/sanfrancisco Follow us on Facebook, Twitter, and YouTube at: www.facebook.com/nwsbayarea www.twitter.com/nwsbayarea www.youtube.com/nwsbayarea  FXUS66 KMTR 231147 AFDMTR Area Forecast Discussion National Weather Service San Francisco Bay Area 447 AM PDT Sun Sep 23 2018 .SYNOPSIS...An upper level trough moving across far northern California will likely maintain a cooling trend for inland areas today. High pressure will begin building inland to our north and east tonight. This will result in dry offshore winds and fire weather concerns for the North Bay Hills from tonight through Tuesday. Also, expect much warmer conditions by Tuesday and Wednesday, with temperatures warming well above seasonal averages. Temperatures will cool late in the week as an upper low approaches from the west. && .DISCUSSION...As of 3:30 AM PDT Sunday...Water vapor satellite imagery shows an upper trough beginning to move across the Pacific Northwest and far northern California early this morning. Would typically expect the marine layer to deepen and onshore flow to increase under such a scenario, but latest observations indicate this is not happening. In fact, latest Fort Ord profiler data shows the marine layer remaining relatively shallow with a depth of about 1000 feet. Also, onshore pressure gradients have been trending weaker. In addition, low clouds early this morning are less extensive compared to 24 hours ago. These factors call into question previous forecast thinking that the cooling trend would continue today, especially inland. Based on current trends, the most likely outcome will be temperatures near persistence in most areas. And, with less coastal stratus, some coastal areas may experience slight warming today. After the upper trough moves off to our east late today, an upper ridge is forecast to build off the coast of the Pacific Northwest and southward along the northern California coast. Also, surface high pressure will build inland to our north and east by late tonight, causing winds in the hills to shift from westerly to north or northeast, especially in the North Bay Mountains. Locally gusty offshore winds in the North Bay Mountains could result in critical fire weather conditions at higher elevations from tonight through Tuesday. See Fire Weather Discussion below for details on the Fire Weather Watch and fire weather concerns. Building high pressure aloft during the first half of the week and weak offshore flow will result in a robust warming trend from Monday through Wednesday. Widespread highs in the 90s are likely across inland areas by Tuesday and Wednesday. Coastal temperatures will be more difficult to predict as they will be very dependent on the strength of offshore flow. Current WRF model indicates very weak onshore flow will prevail at the surface with light offshore flow just above. Such a scenario would mean coastal temps will mostly remain in the 70s to lower 80s. But if offshore flow is stronger than anticipated, coastal areas could warm well into the 80s or even a few lower 90s by Tuesday and Wednesday. The upcoming warm-up will result in uncomfortably warm daytime conditions across much of our area from Tuesday through Thursday, but heat risks are expected to remain low to moderate for the most part due to long autumn nights and cool overnight lows. A rex block is forecast to develop offshore by midweek as an upper low begins to undercut the upper high. The models agree that the low will slowly undercut the ridge and approach the California coast during the second half of the week. Cooling due to the low's approach will likely commence as early as Thursday, but only a slight downturn in temperatures is expected that day. Much more significant cooling is then anticipated by Friday and Saturday. Both the ECMWF and GFS generate spotty light precipitation as the low moves inland by early Saturday. Since this is still 7 days out, will hold off on adding any rain chances to the forecast. The longer range models forecast a second upper low to move onshore by early October. The 00Z ECMWF is particularly interesting with this second system, forecasting widespread significant rainfall across our area on October 1st and 2nd. && .AVIATION...As of 4:47 AM PDT Sunday...In 72 hours it went from clear skies (Thu) to southerly surge stratus/fog (Fri) to widespread coastal stratus/fog (Sat), and now stratus/fog coverage confined to the immediate coast mainly from San Mateo county south to Pt Conception including the Salinas Valley. Satellite also shows a few patches of stratus and fog near Pt Reyes. Inland skies are VFR while on the coast the marine layer remains compressed favoring VLIFR-IFR cigs and visibilities for the morning. The 12z tafs are a blend of persistence and WRF model output. A dry cool frontal boundary, a temporarily steepened northerly pressure gradient, NW winds and additional compression and downslope drying has entered the boundary layer reducing the marine stratus and fog areal coverage as previously described; continuing erosion due to weak cool air advection, not enough to mix out the marine inversion, and NW winds should help lift VLIFR-IFR to VFR fairly quickly later on in the morning. Inland skies continue VFR. Low confidence on stratus and fog coverage tonight into Monday morning. Vicinity of KSFO...VFR tempo IFR cig 12z-15z. Light westerly wind increasing by late morning with gusts possible up to 20-25 knots in the afternoon and evening. VFR forecast tonight and Monday. SFO Bridge Approach...Similar to KSFO. Monterey Bay Terminals...VLIFR-IFR til 17z-18z, VFR patchy MVFR late morning into early afternoon. IFR probably redeveloping tonight and Monday morning. && .FIRE WEATHER...As of 3:00 AM PDT Sunday...Fire Weather Watch remains in effect for the North Bay Mountains from 11 pm Sunday night through Tuesday afternoon. North to Northeast winds will develop over Napa county tonight and drive humidity lower during the pre-dawn hours of Monday. This offshore wind event looks moderate, especially in terms of wind strength, but confidence is pretty high on offshore pattern developing. Fuels remain critically dry, so any new starts will be susceptible to the winds, low humidities and dry fuels. Biggest threat area looks to be Napa county hills, northeast Sonoma county and around Mt Tam. Winds will ease during the day Monday as temperatures warm up around 89. Offshore winds then look to redevelop of similar magnitude Monday night into Tuesday morning, but with an even drier air mass then moving in. Overnight humidity recoveries could then well be confined to around 20 percent or even less. Temperatures are forecast to continue climbing and widespread 90s are likely across inland areas Tuesday and Wednesday. But winds are expected to be light after Tuesday. Cooling is forecast late in the week. && .MARINE...as of 4:06 AM PDT Sunday...A trough will remain nearly stationary along the California coast while strong high pressure becomes stationary off the Pacific Northwest coast. Gusty northwesterly winds will spread across the coastal waters today while onshore winds become gusty over the bays this afternoon and evening. An extension of high pressure will build into the northern Great Basin tonight and again Monday night into Tuesday. Winds over the coastal waters and bays will be much lighter by later Monday, possibly becoming variable or light southerly early Tuesday morning. Westerly to northwesterly winds return Tuesday afternoon into Thursday. && .MTR WATCHES/WARNINGS/ADVISORIES... .Tday...SCA...Pigeon Pt to Pt Pinos 0-10 nm from 9 AM SCA...Pt Arena to Pigeon Pt 10-60 nm SCA...Pigeon Pt to Pt Piedras Blancas 10-60 nm SCA...Pt Pinos to Pt Piedras Blancas 0-10 nm from 9 AM SCA...Pt Arena to Pt Reyes 0-10 nm SCA...Mry Bay from 2 PM && $$ PUBLIC FORECAST: Dykema AVIATION: Canepa MARINE: Canepa FIRE WEATHER: Dykema/Blier/RWW Visit us at www.weather.gov/sanfrancisco Follow us on Facebook, Twitter, and YouTube at: www.facebook.com/nwsbayarea www.twitter.com/nwsbayarea www.youtube.com/nwsbayarea  FXUS66 KMTR 010617 AFDMTR Area Forecast Discussion National Weather Service San Francisco Bay Area 1017 PM PST Thu Jan 31 2019 .SYNOPSIS...A powerful storm system is forecast to produce damaging winds, heavy rainfall, and localized urban and small stream flooding across the entire region from late Friday into Saturday morning. Numerous showers and isolated thunderstorms are expected from Saturday afternoon through Saturday night, along with continued gusty winds. Two cold weather systems will follow for Sunday and Monday, bringing additional widespread showers and dropping snow levels as low as 2000 feet by Monday. Dry but cool weather returns Tuesday through Thursday of next week. && .DISCUSSION...As of 9:25 PM PST Thursday...Residual low level moisture left over from last night's rainfall, plus clear skies this evening, is resulting in patchy fog formation in the North and East Bay Valleys. High clouds are beginning to increase ahead of the developing storm system offshore, but these clouds probably won't have much impact on inhibiting fog formation in favored areas overnight. Forecast updates this evening have included the addition of patchy fog in the North and East Bay Valleys overnight and into early Friday. The primary forecast story continues to be the powerful storm that is beginning to develop well offshore along 135W. Given the degree of model consistency and agreement, forecast confidence is high that this storm system will produce major impacts across our region starting late tomorrow and continuing into Friday night and Saturday. Primary impact will be strong and damaging winds. The 00Z NAM is consistent with previous runs in rapidly deepening a surface cyclone offshore on Friday and Friday night, with a 980 mb low forecast to be centered about 300 miles WNW of San Francisco by 12Z Saturday. Situations like this, with a surface low rapidly deepening off our coast, typically result in some of our strongest wind events. Storm warnings are up for our coastal waters and a High Wind Watch is in effect for all of our land zones from mid afternoon Friday through Friday night. Winds will become quite strong and gusty by late Friday afternoon, but strongest winds are anticipated just ahead of the cold front on Friday night when gusts 50 to 60 mph are likely, with locally higher gusts expected in the hills and near the coast. Widespread power outages are likely on Friday night. Although the front is forecast to move through late Friday night or early on Saturday, the deep surface low is expected to remain offshore and very slowly move eastward and inland late Saturday and Saturday night. So even though strongest winds are anticipated prior to frontal passage late Friday night, winds will remain strong and gusty through Saturday and into Saturday evening and it's likely that at least Wind Advisories will persist through then. Winds are expected to finally subside by Sunday as the low moves inland and fills. Concerning rainfall with the incoming system... Recent models have trended a bit slower with the timing of both the onset of rain and with heaviest rainfall rates. It now appears rain rates won't become heavy until Friday evening in the North Bay and late Friday night into early Saturday elsewhere. Rain rates of one inch per hour are certainly possible along the frontal boundary on Friday night and into early Saturday. Rain rates of this magnitude on nearly saturated soil will result in excessive runoff which will almost certainly lead to flooding of low lying urban areas as storm drains are overwhelmed. In addition, some of the smaller streams and creeks will likely reach bankfull by late Friday night or Saturday morning, and some may exceed bankfull. Due to the somewhat slower timing of the system, the Flash Flood Watch for most of our forecast area has been extended later in time...through Saturday morning. Thus, the Flash Flood Watch is now in effect from Friday evening through Saturday morning. The mainstem rivers such as the Russian, Napa, and Salinas are expected to experience significant rises by late Saturday, but are not currently expected to flood. Widespread showers will continue behind the front through Saturday and Saturday night, and there may be sufficient instability for thunderstorms as well. Two more systems will bring additional widespread shower activity to our region from Sunday into Monday. The first system on Sunday will arrive from the northwest and lower snow levels to about 3500 feet. The second system will drop down the coast from the north and lower snow levels as low as 2000 feet on Monday. These systems, especially the second one on Monday, won't have all that much moisture to work with, but could still generate measurable snow on our higher peaks. Drier, but cool weather is forecast by next Tuesday and Wednesday. && .AVIATION...As of 10:17 PM PST Thursday...Forecast is VFR-MVFR except VLIFR-IFR in patchy fog tonight and Friday morning. Cloud layers increase late tonight through Friday while offshore E-SE winds steadily feed into the leading edge of rain ahead of rapid cyclogenesis developing over the eastern Pacific. Low level wind shear develops and spreads over the entire forecast area Friday evening into Saturday morning. This low will follow a path near and inside 40N and 130W typically followed by historically strong storms with significant impacts. Fog likely tonight, but forecast areal coverage is low confidence. Recent forecast soundings heavily lean toward near surface air reaching saturation at KSTS, KSFO, KOAK, KSJC, KMRY; statistical guidance forecasts fog for KSTS and KAPC. By late evening is when best chances for fog develops. GOES-16 LIFR Probability and Fog Depth products show VLIFR-IFR Santa Cruz county to coastal and southern Monterey county. Visibility at KLVK less than 2 miles in mist/fog on the 06z observation. Cold frontal passage is forecast early Saturday morning with heavy potentially damaging winds and rain up to frontal passage. Gusty winds persist Saturday. Vicinity of KSFO...Latest metar obs show a light wind, temp/dewpoint difference is 3 Celsius and sct-bkn MVFR cloud layer. Cloud layers gradually increase tonight and Friday along with increasing wind and eventually rain later in the day and evening. Low level wind shear is in the taf Friday evening into Saturday morning. SFO Bridge Approach...Similar to SFO. Monterey Bay Terminals...VFR, gradually increasing clouds late tonight and Friday, spotty light drizzle possible. Winds SE tonight increasing steadily later Friday afternoon and evening with rain arriving Friday night; added low level wind shear to the tafs. && .MARINE...as of 9:50 PM PST Thursday...A rapidly developing low pressure system will form over the offshore waters late tonight into Saturday morning. Forecast models show the low deepening to 980 millibars central pressure Saturday morning and stalling over the offshore waters approximately 300 miles west of the Bay Area Saturday before proceeding to pass over the Bay Area late Saturday into Sunday morning. This low will follow a path near and inside 40N and 130W typically followed by historically strong storms with significant impacts. Expect gale to occasional storm force winds as the low crawls eastward over the coastal waters through Saturday night into Sunday morning. This will create dangerous sea conditions for mariners. && .MTR WATCHES/WARNINGS/ADVISORIES... .Tngt...NONE. && $$ PUBLIC FORECAST: Dykema AVIATION/MARINE: Canepa Visit us at www.weather.gov/sanfrancisco Follow us on Facebook, Twitter, and YouTube at: www.facebook.com/nwsbayarea www.twitter.com/nwsbayarea www.youtube.com/nwsbayarea  FXUS66 KMTR 201203 AFDMTR Area Forecast Discussion National Weather Service San Francisco Bay Area 503 AM PDT Sat Apr 20 2019 .SYNOPSIS...A passing cold front will bring cooler weather and coastal drizzle to the Bay Area Saturday. Warmer weather is forecast on Sunday with building high pressure. A more noticeable warming trend will develop early next week with above normal temperatures. && .DISCUSSION...as of 03:03 AM PDT Saturday...A much deeper marine layer is currently impacting the Bay Area ahead of an approaching cold front. Ft Ord puts the depth near 1,800-2,000 feet this morning. Satellite imagery shows another night of widespread coastal and inland valley stratus. Automated sensors around the region also indicate some patchy fog with visibility three to six miles and at times less. Additionally, Half Moon Bay reported a few hours of -RA and drizzle has been observed here at the forecast office. A few other sites around the region tipped 0.01" of precip this morning too. Needless to say, but a very moisture boundary layer is present this morning. Current forecast will continue the mention of morning clouds, fog and drizzle. As for the cold front itself, latest surface analysis puts the front near the far Northern Sonoma county. KMUX radar imagery actually shows a few echoes off the coast, which is likely the front. Not expecting much precip from the front, but more drizzle from the very moist low levels. The cold front is projected to move through the Bay Area today, which will result in cool and cloudy conditions. Forecast highs today will be in the upper 50s to mid 60s at the coast and 60s to lower 70s inland or several degrees below normal. A few low clouds will be possible tonight with some lingering drizzle, especially Monterey/Big Sur area, as the front exits to the east. By Sunday high pressure will begin to build over the region which will kick off a noticeable warming and drying trend. Temperatures on Sunday will warm three to six degrees. High pressure will continue to build into next week and peak Tuesday/Wednesday. Unlike the last warm up this warm up will have some offshore flow support. Latest WRF model indicates decent NE winds at 925mb Monday and Tuesday. Offshore flow will erode any remaining stratus and introduce lower RH values, especially overnight across the N and E Bay Hills. The strength of the ridge is projected to be two to three standard deviations above normal at 500 mb. Simply put, much above normal for this time of year resulting in some rather warm temperatures. By Wednesday, interior portions of Monterey/San Benito could see temperatures in the mid 90s. Other locations around the Bay Area will not be as warm, but 70-80s around the Bay Shoreline and widespread 80s inland. Both Tuesday and Wednesday will see high temperatures as much as 15 degrees above normal. Very subtle cooling on Thursday as flow aloft become more zonal and low level flow becomes more onshore. A bigger drop in temperatures is forecast on Friday and next weekend as an upper level low moves toward the PacNW. Unlike previous model runs the GFS has now backed off on precip chances next weekend and is more inline with the ECMWF. && .AVIATION...as of 5:03 AM PDT Saturday...Ongoing onshore push of stratus ramps up through morning per recent statistical guidance forecasting increasing southwest to west winds by late morning and afternoon. Metar observations range from IFR in patchy drizzle or light rain to MVFR-VFR. LIFR probability satellite imagery shows plenty of coastal stratus and fog converging along the coastline and extending inland. Incoming cold front later today sweeps SE over the area with potential for strong and gusty post frontal winds over a large part of the area this afternoon and evening. Winds will shift to west to northwest and leaving few-sct cloud coverage at lower levels, in general VFR returns late today and tonight as well as for Sunday. Vicinity of KSFO...W-SW wind 10 to 15 knots becoming W by late morning and increasingly strong and gusty with gusts up over 30 knots in the afternoon and evening. Ceiling lifts quickly to MVFR-VFR by late morning. SFO Bridge Approach...Similar to KSFO. Monterey Bay Terminals...Patchy drizzle or light rain in IFR ceilings this morning, ceilings then lifting to MVFR by late morning. Gusty winds developing in the afternoon. VFR tonight and Sunday. && .MARINE...as of 4:43 AM PDT Saturday...An upper level trough and surface cold front will move southeast over the coastal waters and bays later today. Surface high pressure over the eastern Pacific will build in behind the cold front during the weekend and build into the Great Basin early next week. Gusty northwest winds will generate fresh steep seas over the weekend while swell heights remain moderate. && .MTR WATCHES/WARNINGS/ADVISORIES... .Tday...SCA...Pigeon Pt to Pt Pinos 0-10 nm from 9 AM SCA...Pigeon Pt to Pt Piedras Blancas 10-60 nm from 9 AM SCA...Pt Arena to Pt Reyes 0-10 nm SCA...Pt Reyes to Pigeon Pt 0-10 nm SCA...Pt Pinos to Pt Piedras Blancas 0-10 nm SCA...Pt Arena to Pigeon Pt 10-60 nm SCA...SF Bay from 9 AM SCA...Mry Bay from 9 AM && $$ PUBLIC FORECAST: MM AVIATION/MARINE: Canepa Visit us at www.weather.gov/sanfrancisco Follow us on Facebook, Twitter, and YouTube at: www.facebook.com/nwsbayarea www.twitter.com/nwsbayarea www.youtube.com/nwsbayarea  FXUS66 KMTR 121516 AFDMTR Area Forecast Discussion National Weather Service San Francisco Bay Area 816 AM PDT Sun May 12 2019 .SYNOPSIS...Dry weather conditions with temperatures near to slightly above normal will prevail through early this week as high pressure builds over the region. Periods of night and more coastal/valley clouds are also likely given the marine influences. A cooling trend with the potential for shower chances are then expected for the latter half of the week. && .DISCUSSION...as of 08:15 AM PDT Sunday...A 2000 ft marine layer is locked solidly in place across the vast majority of the San Francisco Bay Area and Central Coast this Mothers Days morning. Cloud bases at 800-1200 feet and cloud thicknesses roughly around 1000 feet. Expect to see the marine layer mix out by the mid morning for extreme inland locations, late morning for most urban areas, and as late as the early afternoon closer to the coast. To no surprise, conditions this morning are running very similar to 24 hours ago, with only slightly weaker terrain driven winds this morning. Despite the early cloud coverage, today is expected the be the warmest day of the week as high pressure strengthens aloft. Afternoon highs are forecast to push into the mid to upper 80s for the extreme inland valleys, 70s to low 80s for urban areas, and mid to upper 60s along the coasts and shorelines. These temperatures are a degree or two above seasonal normals for this time of the year. The marine layer will return tonight in time to obscure the night sky along the coast before pushing inland to encompass most of the urban areas by sunrise Monday. The marine layer will feel some exertion from above given the build ridge, meaning bases will be slightly lower and the likelihood of drizzle increases along the coastal ridges. Looking ahead, high pressure will continue to build over California into Monday before transitioning eastward into the Great Basin by Tuesday. A late season Gulf of Alaska trough will then dig southward and begin to encroach on the North Bay late Tuesday into Wednesday. This will introduce cooler, wetter conditions into the region from mid week through the end of the work week. Ensemble members still showing some signs of uncertainty with regards to amounts/coverage, with the current forecast model introducing rain to the North Bay and much of the coast Wednesday night into Thursday, and across the entire region with the arrival of a second pulse later Thursday into Friday. Main forecast challenge of the day will be to fine tune the forecast during this upcoming unsettled weather pattern. .PREVIOUS DISCUSSION...as of 3:15 AM PDT Sunday...With a 2000 foot marine layer, coastal low clouds have spread into and filled inland valleys, as seen on IR satellite imagery. Onshore flow is slightly stronger with 2.4 mb from SFO to SAC as compared to 1.8 mb 24 hours ago. That will keep near-coastal locations with similar temperatures as yesterday, but high pressure aloft will give slightly warmer temps to inland areas today as the marine layer compresses somewhat. An approaching upper level trough will initiate a cooling trend on Monday, which will continue through late in the week. Initially there will be slight cooling Monday as the ridge flattens out and the marine layer deepens. Then more cooling is expected as an upper level low from the Gulf of Alaska approaches the Pacific Northwest. A second and stronger shortwave will deepen off the coast on Wednesday. Some model differences in timing still exist, but the ensemble consensus of rain chances arriving on Wednesday is enough to keep that timing in the forecast. Showers to decrease on Thursday as the system moves to the east. The forecast beyond then is more unclear, so slight chance pops persist in an unsettled pattern. && .AVIATION...as of 05:04 AM PDT Sunday...For 12z tafs. Marine layer this morning remains around 2000 feet per the Fort Ord Profiler. Cloud bases are between 600 and 1500 feet AGL with MVFR/IFR observed at most sites. A few locations remain at VFR, particularly around KSQL and portions of the South Bay where stratus has not developed. Expecting cloud bases to slowly lift around sunrise with breakup occurring between 16-18z at most terminals, similar to Saturday. Light onshore winds will continue this morning and increase this afternoon before decreasing during the evening. With slight compression of the marine layer, return of stratus this evening could occur slightly later than Saturday evening with perhaps lesser extent into the inland valleys. Vicinity of KSFO...MVFR cigs will continue into the morning hours. Expecting breakup of the stratus to occur similar to Saturday morning. Westerly winds will continue and increase this afternoon to around 15 kt. SFO Bridge Approach...SMB surface observations indicate OVC while satellite indicates a hole in the stratus over portions of the approach over the past few hours. Stratus may fill in over the approach around sunrise and then burn off by around 17z. Monterey Bay Terminals...MVFR/IFR cigs at the terminals will continue through the morning hours. VFR conditions expected to develop by 16-17z with visuals through the afternoon. Stratus will reform this evening. Onshore winds will increase this afternoon to 10-15 kt. && .MARINE...as of 07:53 AM PDT Sunday...High pressure will build overhead through early next week. Low pressure inland will result in northwest winds continuing through Monday. Winds will become locally gusty near the coast and bays during the afternoon and evening hours. These winds will generate fresh swell along the coast. A small long period southerly swell will continue through next week. Deteriorating conditions are expected by mid week as a late season front is forecast to move across the waters. && .MTR WATCHES/WARNINGS/ADVISORIES... .Tday...SCA...Pt Arena to Pt Reyes 0-10 nm from 2 PM SCA...Mry Bay from 2 PM SCA...Pigeon Pt to Pt Pinos 0-10 nm from 2 PM SCA...Pt Pinos to Pt Piedras Blancas 0-10 nm SCA...SF Bay from 3 PM && $$ PUBLIC FORECAST: DRP AVIATION: ST MARINE: ST Visit us at www.weather.gov/sanfrancisco Follow us on Facebook, Twitter, and YouTube at: www.facebook.com/nwsbayarea www.twitter.com/nwsbayarea www.youtube.com/nwsbayarea