Area Forecast Discussion National Weather Service Seattle WA 330 AM PDT Sun Apr 26 2015
Synopsis: — a weak warm front will clip Western Washington today and tonight with rain mainly along the coast. High pressure will bring warmer and drier weather on Monday. A pair of fronts will cross the region Tuesday and Wednesday for cooler and wetter weather. An upper level trough will maintain a chance of showers through the end of the week.
Short term: — temps dropped to the 30s to lower 40s early this morning with the skies clearing out. There is some patchy fog in the Southwest interior as well. But clouds will increase across Western WA today as a warm front moves in. This is a weak front with light precip mainly affecting the Olympic peninsula. The warm front will shift North into Southern B. C. Tonight as an upper level ridge builds over the Pacific Northwest. There is a chance of rain in the interior but precip amounts will be patchy and light. It will be warmer overnight with Lows in the middle 40s to lower 50s.
Monday will be warmer and drier as the upper level ridge continues to build over the region. Expect mostly sunny skies with Highs in the 70s across the interior — with 60s along the coast. The ridge will exit East Monday night as a trough digs offshore.
Look for cooler and wetter weather Tuesday and Wednesday. Showers will return on Tuesday as a cold front moves inland. Onshore flow will increase behind the front Tuesday afternoon for breezy S/SW winds. Models show a Puget Sound convergence forming over the Central Sound — and showers from the the Puget Sound convergence zone may linger through Tuesday night. Another cold front will cross the area on Wednesday for another round of showers and breezy weather. Expect Highs in the middle 50s to lower 60s each day. 33
Long-term: — overall confidence in the long range forecast remains low. Models show zonal flow Thursday and Friday. A trough over B. C. May clip Western WA for a chance of showers each day. After that the models disagree on the pattern through the weekend. Therefore will maintain a forecast close to seasonal norms. 33
Aviation: — temporary upper level ridge moving through Western Washington this morning. Weakening front reaching the coast late in the day with the front dissipating as it moves inland tonight into early Monday morning. Air mass stable.
Satellite imagery shows high clouds out ahead of the front have reached the coast and will spread inland over the next couple of hours. Patchy fog over the Southwest interior will only last until around sunrise. Increasing middle level clouds later this morning with the ceilings lowering down to between 5000-8000 feet this afternoon. Rain beginning along the coast in the middle to late afternoon hours with the rain holding off over the interior until the evening hours. Ceilings lowering down to near 4000 feet with the onset of the precipitation. Some Marginal Visual Flight Rules ceilings are possible along the coast this evening.
SeaTac — increasing clouds at or above 15000 feet this morning. Ceilings lowering this afternoon down to near 7000 feet by 5 PM PDT Monday. Chance of rain in the evening hours will ceilings continuing to lower into the 4000-5000 foot range. Southerly winds 4 to 8 knots. Felton
Marine — flat surface gradients this morning with weak high pressure across the area. A weak front will move into the coastal waters later this afternoon. The front will dissipate later tonight as it moves inland. Southerly winds will pick up over the coastal waters in advance of the front with middle to high end Small Craft Advisory winds are expected today into tonight. Southerly winds are forecasted to remain below 20 knots over the inland waters.
After a break on Monday another front will move through the area Tuesday. This system also looks weak with the best chances for Small Craft Advisory winds in the Central and Eastern Strait behind the front.
Forecast confidence is low beyond Tuesday with model solutions varying from run to run. Previous runs had a surface ridge building into the area but the 5 PM PDT GFS is indicating another weak front moving through the waters. Felton
Puget Sound — Small Craft Advisory coastal waters.
You can see an illustrated version of the forecast Discussion: at http://www.weather.gov/seattle/gafd/latest_webafd.html
A complete list of airport weather stations used for the METAR reporting system is at: http://adds.aviationweather.gov/metars/stations.txt . Regional airports weather station designations are at the bottom of this page.
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Acronyms ACARS Aeronautical Radio Communications Addressing Reporting System VFR Visual Flight Rules Numerical Forecast Models Abbreviations CMC Canadian Meteorological Centre ECMWF European Centre for Medium-Range Weather Forecasts GEM Global Environment Multiscale (CMC's short-range model) GFDL Geophysical Fluid Dynamics Laboratory's Hurricane Model GFS Global Forecast System (formerly known as the AVN and MRF) MM5 Penn State University/National Center for Atmospheric Research's Mesoscale Model NAM North American Mesoscale (formerly known as the Eta) NGM Nested Grid Model NOGAPS Navy Operational Global Atmospheric Prediction System RUC Rapid Update Cycle Forecast Model SREF Short Range Ensemble Forecasts UKMET United Kingdom Meteorological Office Washington Airports and other NWS stations elevations in meters N W elev WA ARLINGTON MUNI KAWO 48 10N 122 10W 42 WA BELLINGHAM KBLI 48 48N 122 32W 50 WA WHATCOM (BLI) KHUH 48 57N 122 35W 26 WA BREMERTON NTNL KPWT 47 30N 122 45W 147 WA BURLINGTON/MT V KBVS 48 28N 122 25W 43 WA CHEHALIS CENTRAL KCLS 46 41N 122 59W 54 WA COLVILLE MUNICIP KCQV 48 32N 117 52W 572 WA DEER PARK KDEW 47 58N 117 26W 668 WA EASTSOUND/ORCAS KORS 48 42N 122 54W 8 WA ELLENSBURG KELN 47 02N 120 32W 519 WA EPHRATA KEPH 47 18N 119 31W 383 WA EVERETT KPAE 47 55N 122 17W 180 WA FAIRCHILD AFB KSKA 47 37N 117 39W 750 WA FORT LEWIS/GRAY KGRF 47 04N 122 34W 92 WA FRIDAY HARBOR KFHR 48 31N 123 02W 32 WA HANFORD KHMS 46 34N 119 35W 223 WA HOQUIAM KHQM 46 58N 123 56W 7 WA KELSO LONGVEIW KKLS 46 07N 122 54W 5 WA MOSES LAKE KMWH 47 12N 119 19W 362 WA OAK HARBOR AIRPA K76S 48 15N 122 40W 58 WA OLYMPIA KOLM 46 58N 122 54W 58 WA OMAK KOMK 48 28N 119 31W 395 WA PASCO KPSC 46 16N 119 07W 121 WA PORT ANGELES KCLM 48 07N 123 30W 85 WA PULLMAN/MOSCOW KPUW 46 45N 117 07W 773 WA PUYALLOP/THUN KPLU 47 06N 122 17W 164 WA QUILLAYUTE KUIL 47 56N 124 33W 54 WA RENTON KRNT 47 30N 122 13W 21 WA SEATTLE/BOEING KBFI 47 33N 122 19W 4 WA SEATTLE/METRO KSEA 47 27N 122 19W 136 WA SEATTLE/WFO KSEW 47 27N 122 18W 130 WA SEATTLE/ARTCC KZSE 47 17N 122 11W 99 WA SEATTLE/CAMANO I KATX 48 12N 122 30W 151 WA SHELTON KSHN 47 14N 123 08W 82 WA SPOKANE KOTX 47 41N 117 38W 727 WA SPOKANE/FELTS KSFF 47 41N 117 19W 609 WA SPOKANE/METRO KGEG 47 37N 117 32W 735 WA STAMPEDE PASS KSMP 47 17N 121 20W 1208 WA TACOMA KTIW 47 16N 122 35W 89 WA TACOMA/MC CHORD KTCM 47 07N 122 28W 98 WA TATOOSH/VOR KTOU 48 18N 124 38W 520 WA TOLEDO WINLOCK M KTDO 46 28N 122 47W 113 WA VANCOUVER KVUO 45 37N 122 39W 8 WA WALLA WALLA KALW 46 06N 118 17W 363 WA WENATCHEE KEAT 47 24N 120 12W 377 WA WHIDBEY IS. NAS KNUW 48 21N 122 39W 14 WA YAKIMA KYKM 46 34N 120 32W 324 WA BURLINGTON/MT V K75S 48 28N 122 25W 43 WA COLVILLE K63S 48 32N 117 52W 571 WA DEER PARK K07S 47 58N 117 26W 668 WA DESTRUCTION ISL 47 40N 124 31W 21 WA PORT ANGELES CG KNOW 48 08N 123 25W 4 WA SMITH ISLAND 48 19N 122 10W 15 WA PEARSON/VANCOUVR K60S 45 37N 122 39W 8 WA WEST POINT (LS) 47 40N 122 34W 3 BC ABBOTSFORD AIRPO CYXX 49 01N 122 22W 58 BC AGASSIZ (AUTO) CWZA 49 15N 121 46W 15 BC ENTRANCE IL AUTO CWEL 49 13N 123 47W 5 BC ESQUIMALT METOC CWPF 48 25N 123 25W 12 BC HOPE AIRPORT (MA CYHE 49 22N 121 28W 39 BC HOPE SLIDE CWKV 49 16N 121 13W 674 BC KELP REEFS CWZO 48 33N 123 14W 1 BC MALAHAT (AUTOB) CWKH 48 34N 123 34W 366 BC MERRY ISLAND CWMR 49 28N 123 55W 8 BC MT SICKER RADAR CXSI 48 51N 123 45W 1 BC NANAIMO AIRPORT CYCD 49 02N 123 52W 28 BC P. MEADOWS CS AU CWMM 49 12N 122 40W 5 BC RACE ROCKS AUTOB CWQK 48 17N 123 31W 5 BC SAND headS (LS) CWVF 49 06N 123 18W 1 BC SATURNA ISL (MAP CWEZ 48 46N 123 02W 7 BC SHERINGHAM AUTOB CWSP 48 22N 123 55W 21 BC SQUAMISH (AUTOB) CWSK 49 46N 123 10W 60 BC VANCOUVER (AUTOB CWHC 49 17N 123 07W 2 BC VANCOUVER INTL A CYVR 49 10N 123 10W 2 BC VIC. HARTLAND AU CWVV 48 31N 123 28W 49 BC VICTORIA (AUTOB) CWLM 48 25N 123 19W 70 BC VICTORIA HARBOUR CYWH 48 25N 123 23W 10 BC VICTORIA INTL AR CYYJ 48 38N 123 25W 19 BC VICTORIA UNIV CWYJ 48 28N 123 18W 39 BC W VANCOUVER AUTO CWWA 49 21N 123 10W 178 BC WHITE ROCK AUTOB CWWK 49 01N 122 46W 15