textproduct: Seattle/Tacoma

SYNOPSIS

Upper level low well to the south will weaken and slowly move northeast tonight and Friday. Upper level trough exiting Gulf of Alaska will approach the coast Friday. Convection developing east of the Cascades tonight will weaken and move into the Western Washington interior Friday morning while a marine push increases the low level moisture. Low level onshore flow Friday night and Saturday weakening Sunday with upper level trough weakening and moving inland Saturday night. Upper level ridge trying to build Sunday into the first part of next week with low level offshore flow developing.

SHORT TERM /TODAY THROUGH SATURDAY/

No updates to the AFD this morning - forecast remains on track. -HPR

Satellite imagery shows small area of stratus in Grays Harbor county otherwise just some high clouds over the area this morning. Temperatures at 3am/10z on the mild side, in the 50s.

Upper level low over Central California weakening and moving northeast today while an upper level trough exits the Gulf of Alaska. Western Washington in between these features. Low level flow light with stratus over Grays Harbor county not making it much further inland. Temperatures aloft are warm, 850 mb temps around plus 15C. With plenty of sunshine temperatures over the interior getting into the 70s and lower 80s. Afternoon seabreeze along the coast will keep highs there in the 60s.

Upper level low continuing to move northeast and weaken tonight. Convection developing east of the Cascades this evening weakening and drifting into the Cascades and interior of Western Washington overnight. In the lower levels marine push with gales through the Strait of Juan de Fuca increasing the low level moisture over the area. In all by early Friday morning cloudy skies with at least a chance of showers from the Puget Sound eastward. Lows with the cloud cover near 50.

Shower activity lingering into Friday afternoon for the interior as the air mass cools aloft. 850 mb temperatures down to plus 3 to 5C by late in the afternoon. Low level onshore flow keeping clouds in the lower levels. Much cooler with highs only near 60.

Upper level low weakens into an upper level trough by Friday night and Saturday as it moves into the Northern Rockies. Trough offshore weakens as well and remains offshore through Saturday. Low level onshore flow Friday night weakening Saturday with a little sunshine Saturday afternoon. Highs still a touch below normal, upper 50s to mid 60s. Felton

LONG TERM /SATURDAY NIGHT THROUGH WEDNESDAY/

Extended models in good agreement but not showing much run to run consistency this morning. What is left of the offshore upper level trough moving inland Saturday night into Sunday morning. Upper level ridge beginning to build Sunday afternoon giving the area more sunshine and slightly warmer temperatures. Highs in the 60s.

New wrinkle in the extended solution this morning is instead of the upper level ridge continuing to build over Western Washington with low level offshore flow developing, the operational runs have the remnants of the upper level low over Central California this morning moving west from the Northern Rockies and forming an upper level low over Eastern Washington Monday and Tuesday. The ensembles have the operational run solutions as an outlier and stay with the developing offshore flow scenario for Monday and Tuesday. Given the unusual nature of the operational solutions will keep the warming trend intact Monday and Tuesday with highs in the 70s Monday and 70s to mid 80s Tuesday.

There is better agreement on at least a weak marine push Tuesday night into Wednesday cooling highs back down into the 70s over the interior and mid 60s along the coast.

AVIATION

South to southeast flow aloft is expected today as a closed upper low continues to churn over the Great Basin and a broad upper trough moves into the northeast Pacific. The low level flow will become increasingly onshore today into tonight. The air mass will gradually moisten late today and become somewhat unstable over the higher terrain of the Cascades with isolated showers or thunderstorms. The moisture will spread across the region tonight with ceilings lowering to MVFR in showers by Friday morning.

KSEA...VFR today. Clouds increase tonight with ceilings lowering to MVFR by around 12Z and showers increasing in coverage Friday morning. Surface winds light and variable will become W/NW 7 to 10 knots this afternoon then northerly for a period this evening. Winds are then expected to abruptly back to southerly near or after 03Z and increase to 10 to 15 knots through Friday morning.

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MARINE

High pressure over the offshore and coastal waters will produce onshore flow. The onshore flow will increase late today and Friday as low pressure deepens over interior British Columbia and east of the Cascades. This will result in gusty northwesterly winds and hazardous seas for the coastal waters into Friday with westerly gales in the central and east strait this evening through much of Friday. High pressure will rebuild across the coastal and inland waters this weekend allowing onshore flow to ease and winds subside. Thermally induced low pressure will expand northward near the coast on Tuesday for a brief period of weak offshore flow.

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HYDROLOGY

The daily hydrology discussion has ended until the start of the next rainy season; it will only be updated during this time as needed.

SEW WATCHES/WARNINGS/ADVISORIES

WA...None. PZ...Small Craft Advisory until 3 PM PDT Friday for Grays Harbor Bar.

Small Craft Advisory from 1 PM this afternoon to 5 PM PDT Friday for West Entrance U.S. Waters Strait Of Juan De Fuca.

Gale Warning from 4 PM this afternoon to 11 PM PDT Friday for Central U.S. Waters Strait Of Juan De Fuca-East Entrance U.S. Waters Strait Of Juan De Fuca.

Small Craft Advisory from 5 PM this afternoon to 11 PM PDT Friday for Admiralty Inlet-Northern Inland Waters Including The San Juan Islands.

Small Craft Advisory until 5 PM PDT Friday for Coastal Waters From Cape Flattery To James Island 10 To 60 Nm-Coastal Waters From Cape Flattery To James Island Out 10 Nm- Coastal Waters From James Island To Point Grenville 10 To 60 Nm-Coastal Waters From James Island To Point Grenville Out 10 Nm-Coastal Waters From Point Grenville To Cape Shoalwater 10 To 60 Nm-Coastal Waters From Point Grenville To Cape Shoalwater Out 10 Nm.