Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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000 FXUS66 KSEW 171624 AFDSEW Area Forecast Discussion National Weather Service Seattle WA 924 AM PDT Wed Apr 17 2024 .UPDATE...
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No changes to the overall forecast this morning. Please see the aviation and marine sections below for updates to those forecasts. .PREV DISCUSSION... /issued 412 AM PDT Wed Apr 17 2024/ .SYNOPSIS...Upper level ridge offshore today with dry northerly flow aloft. Dry upper level trough moving down the backside of the ridge over Western Washington late tonight into Thursday night. Weak upper level ridge building over the area Friday with low level offshore flow. Ridge dissipates Friday night with a weakening front arriving Saturday afternoon and evening. Trailing upper level trough moving through Saturday night into Sunday morning. Upper level ridge building offshore Sunday night moving over Western Washington Monday. The ridge will weaken Tuesday.
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&& .SHORT TERM /TODAY THROUGH FRIDAY/...
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Satellite imagery shows clear skies over most of Western Washington this morning. Small patches of stratus have formed over Snohomish county and along the North Coast. With the mostly clear skies temperatures are quite cool for the middle of April, in the upper 20s and 30s. Upper level ridge offshore today with dry northerly flow aloft. What little stratus there is out there will dissipate by late morning. Even with the sunny skies temperatures aloft are a little on the cool side which will keep highs mostly in the 50s and lower 60s. Upper level trough moving down the backside of the ridge will reach Western Washington late tonight and remain over the area into Thursday night. With the over land trajectory of the trough there will be little moisture with it making for another sunny day Thursday. Lows tonight and Thursday night in the 30s and lower 40s. Highs Thursday a little warmer, in the mid 50s to mid 60s. Upper level trough moves off to the east Friday with an upper level ridge building offshore. Low level flow going offshore with gusty easterly winds in the Cascade Foothills. The offshore flow and warming temperatures aloft will result in warmer high temperatures Friday, in the 60s and lower 70s.
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&& .LONG TERM /SATURDAY THROUGH TUESDAY/...
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Models in good agreement with the upper level ridge moving through Western Washington Friday night and a negatively tilted front approaching Saturday. Front moving through Saturday afternoon and evening with rain likely at that time. Trailing upper level trough will keep a chance of showers in the forecast into Sunday. A weak upper level ridge builds into Western Washington Monday for another dry day. Model solutions diverging Tuesday with the ECMWF keeping dry zonal flow aloft while the GFS has another front trying to move into the area. Ensemble solutions are no help so with the uncertainty will have chance pops in the forecast. Highs Saturday in the upper 50s to mid 60s cooling Sunday to the 50s and lower 60s. A little warmer Monday and Tuesday, back into the upper 50s to mid 60s. Felton
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&& .AVIATION...
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Low VFR/MVFR clouds across most of Puget Sound will continue to burn off through the morning hours. The majority of low clouds are spanning north Puget Sound Waters into the Strait of Juan de Fuca, and from Tacoma down into Olympia. Expect the low CIGs to dissipate by 16-17Z this morning, which will give way to clear skies and calm conditions for the rest of the day. Remaining conditions for the TAF forecast are VFR, but cannot rule out a brief period of MVFR stratus along the coast, potentially impacting HQM from 12-16Z (30% chance). Onshore flow will continue to ease with light northerly winds through the day Wednesday, generally 5-10 kt, with gusts to 20 kt possible from 20-02Z at the Puget Sound terminals. KSEA...VFR (with a few low clouds that will dissipate by 16Z), with southeasterly winds early this morning. SE winds continuing through 16Z-17Z, then turning northerly after 18Z. Winds pick back up 8 to 12 kt with occasional gusts to 20 kt possible after 20Z, diminishing by 03Z. Kristell/HPR .MARINE...Northwesterly winds into today as surface high pressure builds over the coastal waters. Winds will turn offshore on Thursday and into Friday as a thermal trough develops along the coast. Relatively calm winds expected through the rest of the week, with the only exception being through the Central Strait of Juan de Fuca, which may see periods of breezy winds Thursday and Friday. The next frontal system will traverse the region on Saturday. Waves will become less steep as seas decrease to 3 to 5 ft early tomorrow and will remain there through the end of the week. Kristell/HPR
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&& .HYDROLOGY...
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No river flooding expected for the next 7 days. .CLIMATE...The warmest 4 day stretch in April in Seattle began on this day in 2016. Four straight days with highs in the 80s, 80 on the 17th, the warmest April day on record 89 on the 18th, 84 on the 19th and 81 on the 20th. Before this event Seattle had only had back to back 80 degree days in April once, April 29 and 30, 1976 and the record for the most 80 degree plus days in the month of April was 2 days ( 1947, 1976 and 1987 ). Felton
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&& .SEW WATCHES/WARNINGS/ADVISORIES...
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WA...None. PZ...None.
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&& $$

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