textproduct: Seattle/Tacoma

SYNOPSIS

A decaying system moving inland has lead to increased cloud cover today but not much in the way of any precipitation. Generally dry conditions should persist into Monday, with a more active system arriving by mid week for additional rain, high elevation snow, and gusty winds.

SHORT TERM /TONIGHT THROUGH TUESDAY NIGHT/

Weak high pressure is building over western Washington this afternoon in the wake of a decaying front. Mild and generally clear conditions are expected through Monday.

The next low pressure system will influence the region beginning Tuesday and lasting through Wednesday. There has been some shifting of the track of the low pressure system, which has impacted the wind forecast, but gusty conditions are expected throughout the area, in addition to high elevation snow and lowland rain. The gustiest locations look to be along the immediate coast and areas from Everett north to the Canadian Border. Winds will peak Tuesday afternoon and evening before decreasing. Snow levels will begin around 2500 to 3500 feet on Tuesday, increasing to 5000 feet and limiting the amount of snow that falls to areas above that elevation. Snow levels drop again to 2000 to 3000 feet on Wednesday, with light accumulations expected through the Cascade passes. Estimates for snowfall are roughly between 1-2 inches at Snoqualmie Pass, and 2-4 inches at Stevens Pass for the duration of the event. These amounts are subject to change as the track of the low changes. Additionally, post frontal convergence zone activity on Wednesday could locally enhance snowfall along the US 2 corridor in through Stevens Pass. The 48 hour probabilities of snowfall greater than 8 inches ending Thursday morning are 25% for Stevens Pass and 20% for Snoqualmie Pass. Lowland rainfall amounts for this event are between 0.5-0.75 inches in Puget Sound, and up to an inch along the immediate coast.

LONG TERM /WEDNESDAY THROUGH SUNDAY/

Active weather continues on Wednesday, with the system forecast to exit on Thursday. Lingering showers will be possible Thursday morning before scattering in the afternoon and evening. The later half of the week appears to be drier as the ridge in the Great Basin amplifies, moving the storm track more into SE AK. Temperatures on Friday and Saturday could rebound into the upper 50s and even low 60s in some locations, giving a more clear taste of spring.

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AVIATION

Zonal flow aloft will prevail across western Washington tonight into Monday. High pressure will build back into the area at the surface in the wake of this morning's front. Satellite imagery shows low clouds continuing to scatter out across the region this afternoon and the majority of the area terminals have rebounded back to VFR conditions as a result. Expect terminals to largely remain VFR throughout the TAF period, with some high cloud cover expected to stream in overhead.

Winds across the Puget Sound terminals have largely shifted back to the north this afternoon, persisting at 4-8 kt. Winds will become light overnight, but will largely remain northerly.

KSEA...VFR conditions expected throughout the TAF period. High clouds will continue to stream into the terminal into Monday. Winds have switched to northerly and persist at 4-8 kt at the terminal this afternoon. Winds will ease overnight, but increase again Monday morning between 18-20Z.

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MARINE

High pressure building back into the area waters this afternoon will remain situated over the region through Monday, maintaining light winds across the area. Seas will hover between 6-8 ft. A deepening low pressure system will then move into the northeastern Pacific on Tuesday, swinging a strong frontal system across the area waters. While uncertainty remains in regards to the exact track of this low pressure system, guidance continues to suggest that strong winds and building seas are likely for the area waters. Latest probabilistic guidance indicates a 75-90% chance of wind gusts exceeding gale force criteria across the coastal waters on Tuesday, and thus have issued a Gale Watch. Seas will build towards 15-19 ft on Tuesday, with latest GEFS guidance still indicating roughly a 40-50% chance of seas exceeding 20 ft for the northwestern portion of the coastal waters. A strong push of westerly winds is likely along the Strait of Juan de Fuca in the wake of the frontal system Tuesday night into Wednesday. Winds will then ease area-wide into Thursday as high pressure starts to build back into the area waters again and remains situated across the region through Friday.

Seas will slowly subside on Wednesday and towards 6-8 ft by Thursday. Seas will hold between this range through Friday.

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HYDROLOGY

The Snohomish River at Snohomish will be dropping below flood stage imminently and that warning is likely to drop off in the next few hours. From then, only the Cedar river at Renton will continue to hover in Minor Flood until later on Monday evening. Despite additional rainfall coming with the midweek system, no additional river flooding is expected but small rises on area rivers is possible.

SEW WATCHES/WARNINGS/ADVISORIES

WA...None. PZ...Gale Watch from late Monday night through Tuesday evening 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.