FXUS66 KPQR 251539 AFDPQR AREA FORECAST DISCUSSION NATIONAL WEATHER SERVICE PORTLAND OR 839 AM PDT FRI OCT 25 2013 .SYNOPSIS...AN UPPER LEVEL RIDGE WILL REMAIN OVER THE PACIFIC NORTHWEST THROUGH SATURDAY. A VERY WEAK UPPER LOW WAS NEAR VANCOUVER ISLAND THIS MORNING AND WILL DRIFT INTO NORTHWEST WASHINGTON TODAY AND TONIGHT...THEN SLIDE SOUTH TO THE NORTH OREGON COAST SATURDAY. A COLDER BUT RELATIVELY DRY SYSTEM WILL DROP SOUTH OUT OF BRITISH COLUMBIA AND THROUGH SOUTHWEST WASHINGTON AND NORTHWEST OREGON SUNDAY. BRISK NORTH TO NORTHEAST FLOW ALOFT PREVAILS EARLY NEXT WEEK. THE NEXT THREAT OF RAIN MAY OCCUR MID TO LATE NEXT WEEK. && .SHORT TERM...BIGGEST DIFFERENCE THIS MORNING COMPARED TO 24 HOURS AGO IS THE MUCH DEEPER MARINE LAYER. THE 12Z KSLE SOUNDING INDICATED TOPS TO AROUND 2500 FT. NESDIS EXPERIMENTAL FOG DEPTH IMAGERY AT 14Z INDICATED DEPTHS TO AROUND 1500 FT IN THE NORTH AND CENTRAL WILLAMETTE VALLEY AS WELL AS THE COAST. THE LOW-LEVEL OFFSHORE GRADIENT OF THE PAST COUPLE OF DAYS HAS PRETTY MUCH VANISHED. THE 15Z KTTD-KDLS GRADIENT WAS -0.3 MB. SYNOPTICALLY...A WEAKENING UPPER LEVEL RIDGE WILL REMAIN OVER THE PACIFIC NORTHWEST TODAY INTO SATURDAY. A WEAK BUT COMPACT AND RATHER DRY LOW PRESSURE CENTER WAS NEAR VANCOUVER ISLAND THIS MORNING... WHICH IS CLOSE ENOUGH TO HELP MAINTAIN THE GROWING MARINE LAYER ALONG THE SOUTH WASHINGTON AND NORTHWEST OREGON COAST. THE CENTRAL AND SOUTH WILLAMETTE VALLEY WILL HAVE A TOUGH TIME CLEARING TODAY. ANY CLEARING WILL OCCUR LATE IN THE DAY AND BE SHORT-LIVED. MADE SOME ADJUSTMENTS TO TODAYS MAX TEMPS. THE SUBSIDENCE INVERSION WILL BE AT LEAST 1000 TO 1500 FEET HIGHER TODAY COMPARED TO THE PAST COUPLE OF DAYS. THUS...THE COAST RANGE AND CASCADE FOOTHILLS SHOULD BE SEVERAL DEGREES COOLER. SATURDAY WILL BE SIMILAR TO TODAY. CLOUDS WILL INCREASE AGAIN TONIGHT AND BE VERY SLOW TO CLEAR IF THEY DO AT ALL ON SATURDAY. THE STRAY UPPER LOW SAGS SOUTH TO THE N OREGON COAST BY 18Z SAT. MODELS CONTINUE TO SHOW MINIMAL QPF WITH THIS LOW...KEEPING ANY THREAT NEAR THE LOW CENTER. EXPECT ANY PRECIPITATION THAT OCCURS SAT MORNING WILL BE MAINLY DRIZZLE OR SPRINKLES AS THE MOISTURE IS SHALLOW AND THERE IS NOT ENOUGH COLD AIR TO CREATE STEEP ENOUGH MID-LEVEL LAPSE RATES TO BREAK OR OVERTURN THE MARINE INVERSION. WE WILL BE IN BETWEEN SYSTEMS SATURDAY NIGHT...THOUGH EXPECT MORE AREAS OF FOG AND LOW CLOUDS TO DEVELOP. THEN A COLDER SYSTEM WILL DROP IN FROM THE NORTH ACROSS SOUTHWEST WASHINGTON AND NORTHWEST OREGON ON SUNDAY. THE TRAJECTORY OF THIS SYSTEM WILL LIMIT ANY MOISTURE...BUT SOME VERY LIGHT PRECIPITATION IS POSSIBLE ESPECIALLY NEAR THE COAST AND OVER THE CASCADES. THERE IS A SMALL CHANCE OF SPRINKLES OR DRIZZLE IN THE NORTHERN VALLEYS AS WELL. HAVE FOLLOWED THE ECMWF MODEL FOR THIS. WEISHAAR .LONG TERM...AS THE SUNDAY SYSTEM DIGS SOUTH SUNDAY NIGHT INTO MONDAY...DRY BUT COOL NORTHERLY FLOW SPREADS IN AND RESULTS IN SOME OFFSHORE NORTH TO NORTHEAST FLOW DEVELOPING...WHICH WILL DECREASE THE AREAS OF FOG AND LOW CLOUDS. COLD ADVECTION WILL KEEP AFTERNOON TEMPS IN THE 50S MONDAY...WHILE MORNING TEMPS MAY FALL WELL INTO THE 30S. A BRIEF LOW AMPLITUDE UPPER RIDGE PROMISES DRY WEATHER CONTINUING TUESDAY AS WELL. THEN THE MODELS ARE ADVERTISING A TREND TOWARD A MORE ZONAL THOUGH SLIGHTLY ANTICYCLONIC UPPER AIR PATTERN DEVELOPING FOR THE LATTER PART OF NEXT WEEK...BRINGING IN A CHANCE OF PRECIPITATION TO SOUTHWEST WASHINGTON AND NORTHWEST OREGON AT TIMES. WITH A PAIR OF TYPHOONS CURRENTLY ABOUT TO BE ABSORBED INTO THE WESTERLIES IN THE WESTERN PACIFIC NEAR JAPAN...THESE TRENDS SEEM REASONABLE...AND COULD EVEN ULTIMATELY RESULT IN MORE RAIN THAN CURRENTLY FORECAST. THESE TYPHOONS COULD RESULT IN SOME INSTABILITY IN MODEL SOLUTIONS FOR A WHILE FOR LATER NEXT WEEK AS WELL. HAVE TRENDED THE FORECAST POPS UP A SMALL AMOUNT FOR LATER NEXT WEEK BUT EXPECT MORE ADJUSTMENTS WILL EVENTUALLY BE NEEDED. TOLLESON && .AVIATION...NO UPDATES. PREVIOUS DISCUSSION FOLLOWS. WEAK HIGH PRES OVER THE NE PAC WILL MAINTAIN LIGHT ONSHORE FLOW THROUGH TONIGHT. AIR MASS UP TO ABOUT 2000 FT WILL REMAIN VERY MOIST THROUGH TONIGHT...WITH WIDESPREAD IFR STRATUS AND AREAS OF FOG OVER THE INTERIOR. BUT ALONG COAST...MOSTLY MVFR STRATUS AS MARINE LAYER THERE IS A BIT DEEPER. WILL TAKE MOST OF THE DAY FOR THE CLOUDS/FOG TO BREAK UP. HOWEVER...LOW CLOUDS LIKELY TO REFORM QUICKLY AFTER 05Z TONIGHT. KPDX AND APPROACHES...IFR CIGS/MVFR VIS WILL PERSIST THIS AM. AFTER 19Z...VIS WILL IMPROVE BUT IT WILL TAKE UNTIL 21Z OR 22Z FOR CIGS TO BREAK UP. && .MARINE...MINOR UPDATE TO INCREASE WINDS SLIGHTLY THIS AFTERNOON AND EVENING...OTHERWISE FORECAST LOOKS GOOD. PREVIOUS DISCUSSION FOLLOWS. BENIGN CONDITIONS OVER THE WATERS THROUGH EARLY SAT WITH N TO NW WINDS AROUND 15 KT OR LESS AND SEAS 3 TO 4 FT. A DISTURBANCE WILL DROP DOWN FROM THE NORTH ON SAT WHICH LOOKS TO BRING A PERIOD OF GUSTY LOW END SMALL CRAFT ADVISORY WINDS EARLY SATURDAY THROUGH THE EVENING HOURS. HIGH PRES WILL BUILD OVER INLAND PAC NW BEHIND THE SAT SYSTEM. THIS WILL BRING MODERATE EAST TO NORTHEAST WINDS TO THE REGION...WITH GUSTS UP TO 25 KT IN GAPS OF COASTAL TERRAIN. SEAS BRIEFLY BUILD UP TO 7 OR 8 FT LATE SAT AND SUN... THEN EASE BACK TO 5 FT. MODELS INDICATE RETURN TO MORE SEASONABLE WEATHER TOWARDS END OF NEXT WEEK. WITH APPROACHING LOWS OVER THE GULF OF ALASKA...WILL HAVE W SWELL BUILDING...REACHING NEAR 10 FT BY THU/FRI. ROCKEY. && .PQR WATCHES/WARNINGS/ADVISORIES... OR...NONE. WA...NONE. PZ...NONE. && $$ MORE WEATHER INFORMATION ONLINE AT... HTTP://WEATHER.GOV/PORTLAND INTERACT WITH US VIA SOCIAL MEDIA WWW.FACEBOOK.COM/US.NATIONALWEATHERSERVICE.PORTLAND.GOV WWW.TWITTER.COM/NWSPORTLAND THIS DISCUSSION IS FOR NORTHWEST OREGON AND SOUTHWEST WASHINGTON FROM THE CASCADE CREST TO 60 NAUTICAL MILES OFFSHORE. THE AREA IS COMMONLY REFERRED TO AS THE FORECAST AREA.  FXUS66 KPQR 151051 AFDPQR Area Forecast Discussion National Weather Service Portland OR 250 AM PST Thu Nov 15 2018 .SYNOPSIS...Today will be mostly dry and cloudy with northwest flow. A weak disturbance moving near the area may produce light rain for sw Washington tonight and Friday. Dry weather expected Friday night through early next week as strong high pressure returns to the area. East winds will develop Friday night and result in mostly sunny but cool weather this weekend. Rain is possible mid next week. && .SHORT TERM...Today through Sunday...Low clouds and patchy fog are filling in along the coast and the interior valleys early this morning. A building upper level ridge will keep rain well north of the area today, but a shortwave upper level trough riding over the ridge may bring periods of light rain to extreme sw Washington tonight through Friday afternoon. The upper ridge strengthens Friday evening and N-NE winds develop. Mixing at the lower levels will be poor, especially on Friday and the stagnant air may compromise the air quality. East winds increase Saturday morning as models forecast the Dalles to Troutdale surface pressure gradient of 7 to 9 mb by 8 AM.These winds will dominate through Sunday limiting fog and low clouds at night, and supporting dry weather with mostly sunny skies and cool breezes. Wind gusts of 30 to 35 mph are possible for the east Portland metro area and 65 to 75 mph gusts at Crown point. The east winds should help improve air quality near the Cascade gaps and the Columbia River Gorge, but poor air quality is likely in areas protected from the east winds. ~TJ .LONG TERM...No Changes. Previous discussion follows...Sunday night through Wednesday. The strong upper level ridge over the eastern Pacific shifts inland over the Pacific Northwest. East winds will likely persist through the Columbia River Gorge for the start of next week, but elsewhere winds will remain rather light which could lead to stagnant conditions under the developing inversion. This pattern will remain in place through at least early Tuesday until the next front arrives, but forecast models diverge more significantly by midweek. In particular, the deterministic ECMWF is about 24 hours faster with the next frontal system, bringing it into the region early Tuesday. Trended the forecast towards the NBM, which better reflects the timing in the GFS and ensemble mean solutions. This brings the highest (likely category) PoPs into the region early Wednesday. Cullen && .AVIATION...Varied flight conditions across the area with MVFR to LIFR west of the coast range while interior locations have predominantly MVFR cigs/vis. There are spots of IFR developing and satellite IFR probably showing about 60 to 80 percent chance at interior TAF sites. Various MOS guidance also indicating IFR cigs/vis through around 18Z so will allow for that in the next TAF package. Should see improvement for the afternoon with MVFR to VFR conditions. Later tonight into Friday will probably see areas of IFR returning for the interior. Coastal areas may have enough offshore wind to remain VFR. PDX AND APPROACHES...MVFR prevailing with mist and cigs around 1500-2500 ft in the area. There is still a decent chance (roughly 60 percent) that cigs/vsbys may lower into the IFR category through 18Z or so. MVFR should continue into the afternoon and probably return tonight. /mh && .MARINE...A ridge of high pressure will lay over the waters into Friday, then high pressure will strengthen inland for increasing N-NE flow through the weekend. Some localized gusts 25-30 kt will be possible in the offshore flow over the weekend, mainly below gaps in the coastal terrain. /mh Seas around 10 ft will spread across the waters this morning and is expected to subside below 10 ft this evening. The incoming west swell is likely to lead to Rough Columbia River Bar conditions during the ebbs today and tonight. && .PQR WATCHES/WARNINGS/ADVISORIES... OR...None. WA...None. PZ...Small Craft Advisory for hazardous seas until 8 PM PST this evening for Coastal Waters from Cape Shoalwater WA to Florence OR out 60 NM. Small Craft Advisory for Rough Columbia River Bar from 8 AM this morning to 1 PM PST this afternoon. Small Craft Advisory for Rough Columbia River Bar from 5 PM this afternoon to midnight PST tonight. && $$ Interact with us via social media: www.facebook.com/NWSPortland www.twitter.com/NWSPortland This discussion is for Northwest Oregon and Southwest Washington from the Cascade crest to 60 nautical miles offshore. This area is commonly referred to as the forecast area.