Area Forecast Discussion National Weather Service Seattle WA 910 PM PDT Saturday Oct 25 2014
Synopsis: — a deep low will reach the coast late this afternoon and then fill as it moves Northeast. Rain and very windy conditions will occur this evening over Western Washington. Sunday and Monday will be showery. Another weather system will arrive Tuesday. Wet and breezy weather is likely at times through the end of the week.
Short term: — a deep surface low has been tracking Northeast through Western Washington this evening. Southerly gradients behind the low are probably currently peaking and are strong enough to support at least spotty high wind. Warnings are in effect for Central and South parts of the interior along with the coast for strong West winds. In addition — wind advisories are up for the North interior where gradients are expected to be not quite as strong. Winds should begin subsiding late this evening and continue slowly easing after midnight.
Rain has mostly changed to showers this evening as the frontal system moves inland. Snow levels will drop to 4500-5000 feet tonight. Spots above 5000 feet in the Cascades like paradise on mount rainier could pick up at least a few inches of snow by Sunday morning.
Showers will linger Sunday — then mostly end Sunday night as high pressure aloft builds overhead. After a dry start to Monday — rain should develop at the coast — then spread inland late in the day as the next frontal system approaches.
Most of the rain and wind with this system will occur Monday night. A 980 millibars surface low will move inland North of Vancouver Island early Tuesday morning. This is a typical Southeast sucker wind pattern — windy for the coast and North interior. Wind Advisory strength winds for these areas look like a good bet and marginal high wind is possible but it is too far out to worry about that for now. Rain will change to showers Tuesday behind the front with easing winds. Schneider
Long-term: — previous Discussion: — Wednesday appears to be a mostly cloudy day with scattered showers. Another organized system arrives Thursday. At this point the GFS and Euro diverge with the Euro staying wet and the GFS turning showery. Not confident on any details but the forecast will stay moist into the weekend. Burke
Hydrology — the Skokomish river is rising again in response to heavy rain today and tonight. It is possible the river will get close to flood stage tonight. For now the forecast takes the stage at potlatch to between 15.5 and 16 feet. Flood stage is 16.5 feet.
A break in the rain will allow the Skokomish to recede river Monday. Another front Monday night and Tuesday will bring 2-3 inches of rain to the Skokomish basin. Will need to keep a Watch on this but the
Current forecast keeps the river below flood stage.
Otherwise — flooding on other rivers is unlikely over the next 7 days. Burke
Aviation: — a 991 millibars surface low over Southern B. C. Will continue moving Northeast tonight while higher pressure builds inland over West WA. Very strong West Northwest onshore flow will gradually weaken — allowing strong surface winds to diminish overnight. An upper level trough over the area will move East tonight — but another upper level shortwave trough will move down the B. C. Coast and over West WA Sunday. This will keep showers going over the area through this weekend. Conditions will be a mix of Visual Flight Rules and Marginal Visual Flight Rules — with Marginal Visual Flight Rules ceilings most likely around Puget Sound and around showers.
SeaTac — as of 9 PM PDT strong Southwest surface winds have probably peaked this evening and will gradually diminish the rest of tonight. The Portland Bellingham pressure gradient has begun to weaken. Onshore flow will keep showers going over the area through Sunday. This will keep ceilings a mix of Marginal Visual Flight Rules and Visual Flight Rules from 1000-4000 ft. Kam
Marine — a 991 millibars surface low over Southern B. C. Will continue moving Northeast tonight — while higher pressure builds inland over West WA. Extremely strong West Northwest onshore is producing Gales over all waters — which will peak in the next few hours — then gradually diminish overnight. The hrrr model has been handling the pattern pretty well. Even though high pressure is building inland tonight — a surface trough will remain over West WA through much of Sunday. An offshore surface ridge will finally move over the area Sunday night and Monday. Models remain on track with the next frontal system approaching the area Monday — then reaching the coast Monday night. It looks like a round of more typical Gales for the coast and Northern interior waters. After a post frontal trough on Tuesday — another surface ridge will build over the area middle next week. Kam
WA — High Wind Warning coast — Southwest interior — Seattle/Tacoma metropolitan area. Wind Advisory Northwest interior and East Puget Sound lowlands.
Puget Sound —
Gale Warning all waters. Small Craft Advisory for rough bar conditions Grays Harbor.
You can see an illustrated version of this 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