Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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000 FXUS66 KSEW 172227 CCA AFDSEW Area Forecast Discussion National Weather Service Seattle WA 322 PM PDT Wed Apr 17 2024 .SYNOPSIS...
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Dry spring time weather with cool overnight temperatures and warmer than normal high temperatures will linger through the end of the work week. A weakening front will bring increased clouds, cooler temperature, and widespread precipitation Saturday afternoon and evening followed by lingering showers Sunday. Warmer and dry weather will kick the new week off Monday.
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&& .SHORT TERM /TONIGHT THROUGH SATURDAY/...Sunny skies with widespread temperatures in the mid to upper 50s this afternoon. Mild conditions will linger into the evening setting up another night with temperatures on the cool side of normal. HREF and NBM ensemble data showing a 20-30% chance of temps dipping to freezing again tonight in the lowlands - mainly limited to Lewis County - cool, but a bit warmer than last night. An upper level trough moving down the backside of the offshore ridge late tonight and is expected to linger in the area into Thursday night. This continues to be a dry feature with perhaps a few more mid and high clouds and another sunny day. Thursday highs will be a little warmer - pretty solidly in the 60s. Friday looks to be the warmest day as the upper level trough kicks east, and the offshore upper level ridge building. Importantly low level flow becomes more easterly with gusty easterly winds in the Cascade Foothills. High temperatures will tip a bit higher into the upper 60s and lower 70s. .LONG TERM /SUNDAY THROUGH WEDNESDAY/...The distribution in the ensembles continue to highlight the offshore ridge moving through Western Washington Friday night followed by a negatively tilted front Saturday. This will bring widespread rain and some gusty winds then lingering showers Sunday. There looks to be a good chance an high pressure to some degree Monday with drier and warmer weather to open the new week. There are enough members that keep some potential for precip Tuesday, but there are higher odds for generally dry weather lingering into mid week - typical Spring weather either way. && .AVIATION...VFR skies (with cumulus over in the Cascades and Olympics) will continue this afternoon and into Thursday as upper level ridging continues to build offshore over the Pacific Ocean (with a thermal trough underneath). The ridge building and moving inland on Thursday will decrease the chance for morning clouds and low visibilities (compared to earlier today), but cannot rule out a couple isolated areas seeing patchy fog or frost early Thursday morning (due to weak north flow aloft). Winds at the surface will remain northerly through the forecast, with areas along the coast turning easterly as the ridge moves over Thursday. The highest winds will occur Wednesday/Thursday with 14 to 20 kt gusts possible. KSEA...VFR skies with cumulus east in the Cascades gradually decreasing as an upper level ridge moves in. Winds will remain northerly through the TAF period, with gusty winds up to 15 to 20 kt possible this afternoon/Thursday afternoon. HPR .MARINE...An upper level ridge will continue to build offshore over the Pacific, and will move inland on Thursday. A surface trough will also remain over the coast Thursday into Friday. Gusty east winds of 10 to 20 kt are possible in the Strait of Juan de Fuca Thursday, as well as gusty northerly winds in the Puget Sound waters of up to 20 kt. Small probability that the winds exceed 20 kt, will continue to monitor the potential need for a small craft advisory Thursday for these areas. A trough and surface system will impact the region this weekend, with gusty winds possible in some of the inland and coastal waters Friday through Monday. Expect seas to remain around 3 to 6 ft through the period. HPR && .HYDROLOGY...No river flooding expected for the next 7 days. && .SEW WATCHES/WARNINGS/ADVISORIES... WA...None. PZ...None. && $$

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