![National Oceanic and Atmospheric Administration](/build/images/header/noaa.d87e0251.png)
![National Weather Service](/build/images/header/nws.4e6585d8.png)
![United States Department of Commerce](/build/images/header/doc.b38ba91a.png)
Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA
Issued by NWS Seattle/Tacoma, WA
970 FXUS66 KSEW 291722 AFDSEW Area Forecast Discussion National Weather Service Seattle WA 1022 AM PDT Sat Jun 29 2024 .SYNOPSIS...Southwesterly flow aloft today with upper level ridge well to the east and a weakening front moving into the area late in the day. Front dissipating tonight. Upper level trough moving through Sunday keeping a chance of showers in the forecast. Upper level ridge building offshore Monday will drift slowly eastward moving over the area Thursday and Friday. Warmest day of the year possible Friday. && .SHORT TERM /TODAY THROUGH MONDAY/...Forecast remains on track this morning with some variable high clouds streaming through the area. No updates required, and the remainder of the previous short term section follows. Middle and high level clouds continuing to stream over the area this morning. Clouds thickening up this afternoon with the front close enough for a chance of showers west of Puget Sound in the afternoon. Air mass somewhat unstable over the Cascades and with increasing middle level moisture ahead of the front could see a shower there as well in the afternoon. Highs in the mid 60s along the coast and upper 60s to mid 70s inland. What is left of the front moving inland tonight giving most of the area a chance of showers this evening. With the front lifting to the northeast the chances for showers will linger over the northern portion of the area after midnight. Like this morning, with plenty of cloud cover low temperatures will be mild, in the mid 50s to lower 60s. Weak upper level trough behind the front moving through Sunday keeping at least mostly cloudy skies and a chance of showers in the forecast. Trough axis moving through midday. Increasing onshore flow behind the trough axis with a convergence zone developing over Snohomish county in the afternoon. Little change in the high temperatures with mid 60s coast and upper 60s to mid 70s inland. Upper level trough continuing to move east Sunday night. Chance of showers becoming confined to the Cascades and the convergence zone over Snohomish county in the evening. Convergence zone will last into the morning hours Monday. Outside of the Cascades and convergence zone some clearing Sunday evening but with the low level onshore flow clouds will fill back in overnight. Lows in the 50s. Weak trofiness over Western Washington Monday morning with 500 mb heights rising in the afternoon as an upper level ridge begins to build offshore. The combination of weak trofiness and a dying convergence zone will keep a chance of showers in the morning from about Snoqualmie Pass northward. Morning clouds over the lowlands giving way to afternoon sunshine with the subsidence from the upper level ridge building taking care of the morning marine layer. Highs once again in the mid 60s along the coast and upper 60s to mid 70s inland. .LONG TERM /TUESDAY THROUGH FRIDAY/...Extended models in good agreement with what looks like the beginning of the summer pattern setting up over the Pacific Northwest through the period. Upper level ridge offshore slowly drifting east ending up over Western Washington Thursday and Friday. Low level onshore flow Tuesday and Wednesday weakening Thursday and Friday. Low level flow never really turns offshore late in the week. 500 mb heights peaking around 590 dms Thursday into Friday. 850 mb temperatures in the single digits Tuesday warming to near plus 20C by Friday. With temperatures aloft this warm even without offshore flow warmest locations will be pushing 90 degrees Friday. Areas of morning clouds with afternoon sun Tuesday and Wednesday. Mostly sunny Thursday and Friday. Highs Tuesday in the mid 60s along the coast with upper 60s to mid 70s inland. Highs a couple of degrees warmer Wednesday and Thursday. By Friday, highs in the 70s along the coast and upper 70s to near 90 inland. Felton && .AVIATION...Flow aloft today will become southwesterly ahead of a shortwave trough approaching from the west today (ridging also located east of the Cascades). A weak front will bring the chance of showers today over the Olympics, as well as along the Cascade crest. Activity is expected to move in a northerly direction. Brief heavy downpours may temporarily reduce VIS/CIGs and produce gusty/variable winds (in and around terminals). A few terminals are seeing easterly winds off the Cascades this morning. As the trough approaches, expect the winds to become westerly to southwesterly throughout the day at 6 to 10 kt. CIGs will begin to fill in late this morning/afternoon around 10,000 ft, and drop to MVFR as moisture works its way inland from the coast. There is a slight chance of IFR for terminals along and west of Puget Sound Sunday morning that will scatter later in the day Sunday. KSEA...VFR conditions through most of Saturday. Slight chance of showers from 17Z-02Z Sunday (most of the activity may stay west of the terminal). CIGs gradually lowering to MVFR after 04Z Sunday (slight chance of IFR if enough moisture mixes down). Few easterly winds this morning at 6 kt will become westerly late this morning/afternoon, then becoming southerly after 02Z Sunday. HPR && .MARINE...A weak frontal system will move through the coastal waters today reaching the inland waters late. Showers will be possible Saturday afternoon and evening (a few may be heavy enough to reduce visibilities over the east Strait of Juan de Fuca and Puget Sound waters). The front will dissipate over the inland waters tonight. High pressure builds offshore Sunday, and will send a few pushes through the Strait of Juan de Fuca through early next week. There`s a slight chance west winds may exceed 20 kt Sunday afternoon/evening in the central/east Strati of Juan de Fuca sections (better chance for Monday). Seas will reach 4 to 6 feet today, and remain at 4 to 6 feet through the forecast period. Felton/HPR && .SEW WATCHES/WARNINGS/ADVISORIES... WA...None. PZ...None. && $$