National Weather Service (2024)

Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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-- Discussion containing changed information from previous version are highlighted. --739FXUS66 KSEW 261618 CCAAFDSEWArea Forecast Discussion...CORRECTEDNational Weather Service Seattle WA918 AM PDT Wed Jun 26 2024.UPDATE...Quick update to add thunderstorm mention this morningalong the Cascade crest. Mid-level instability remains a bitstronger than expected and the leading moisture is producingclusters of isolated thunderstorms near the Cascades from southto north this morning. Expect this trend to continue with gustywinds and lightning as the predominant threat from these storms.Meanwhile, more widespread precipitation continues to move eastinto the Olympic Peninsula this morning ahead of the approachingfront. Cullen&&.SYNOPSIS...A shift in the pattern will bring the next uppertrough to the Pacific Northwest, bringing cooler temperatures,breezy winds, and the return of precipitation today and Thursday.Isolated thunderstorms are also expected near the Cascades today. Thecycle then repeats with dry and warmer conditions Friday ahead ofthe next disturbance that reaches the area over the weekend.&&.SHORT TERM /TODAY THROUGH FRIDAY/...A pattern change bringscooler and wetter weather back to western WA as an upper level lowmoves through the Pac NW. For today, showers will be mostlyconcentrated along the coast and in the mountains with justisolated to scattered coverage in the interior. The air mass ismost unstable along the Cascade crest and there is a chance ofthunderstorms too, especially in the North Cascades. We`re inpost-frontal onshore flow tonight with ongoing showers and aconvergence zone over the north sound. Winds will be gusty in thecentral interior and south sound in the 20-30 MPH range. With thecooler air mass in place, temps will drop a few degrees coolerthan average with highs in the 60s along the coast and near 70 inthe interior.Onshore flow continues into Thursday as the upper low shiftsslowly E/NE toward southern Alberta. For western WA, plenty moreshowers, especially over the coast and mountains, as the lowlevel air mass remains moist. Convergence zone showers willcontinue too, focused along the King/Snohomish line. Temperatureswill continue to trend below average with highs in the 60s.High pressure rebuilds over the region on Friday as the upper lowdeparts. Look for drier weather with near average temps. 33.LONG TERM /SATURDAY THROUGH TUESDAY/...Blocking high pressure,centered over the Rockies, keeps systems offshore as we move intoSaturday. Wetter weather returns again Saturday night and Sundayas the ridge shifts east and a trough rotates through western WA.Weak high pressure nudges inland early next week with a few lightshowers mainly over the coast and mountains. 33&&.AVIATION...
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South-southwesterly flow aloft this morning as anupper level trough approaches W WA along with a associated coldfront at the surface. Mid and high level clouds continue to streaminto the region ahead of the aforementioned front and radar thismorning shows widespread precipitation gradually making its wayinland along the coast. Thunderstorms have also started to moveup from the south along the Cascade crest this morning and willcontinue to make their way northward over the next few hours.Current conditions at the majority of the TAF sites remains VFRthis morning, with the exception of MVFR conditions at KHQM asrain starts to move in. Ceilings along the coast and southwestinterior have already started to lower, but expect overallceilings across the interior to gradually lower through theafternoon and evening as the front crosses over the area. Latestguidance suggests ceilings lowering to MVFR across the interiorterminals after 00z. A few localized pockets of IFR to LIFR willbe possible in any heavier showers. Expect lower ceilings tocontinue across the region through the evening and into most ofthe overnight hours as showers persist throughout the area.Winds have transitioned back to the S/SW and will increase toaround 12 to 17 knots, with gusts up to 20 to 25 knots possiblethroughout the afternoon. Winds will start to gradually ease up to8 to 12 knots around 04z-06z.KSEA...VFR conditions will continue through the first part of theday. Winds have transitioned to S/SW this morning and will increaseto around 12 to 16 knots between 15-18z. Gusts around 20 to 25knots will be possible at times through the afternoon. Rainshowers will start to move through the terminal 04z-06z withceilings expected to lower to MVFR through the overnight period.Maz/Borth
-- End Changed Discussion --&&.MARINE...A frontal system will move through the area waters thismorning and into the afternoon, with breezy south-southwesterlywinds throughout the interior waters. Guidance still shows smallcraft advisory strength westerlies through the Strait of Juan DeFuca this morning through the afternoon, maintaining around 20 to30 kts. Southerlies will also increase throughout the Puget Soundwaters this afternoon (15 to 25 kts) before gradually decreasinginto the evening as the front passes through.Weak high pressure looks to build offshore briefly throughout theend of the week, with diurnal pushes down the Strait likely attimes. Additional systems look to push through the area watersthrough the weekend and into the first part of next week.Coastal seas 3 to 5 feet this morning will generally maintainthrough Friday, before increasing to 4 to 6 feet over the weekend.Maz&&.SEW WATCHES/WARNINGS/ADVISORIES...WA...None.PZ...Small Craft Advisory until 11 PM PDT this evening for Central U.S. Waters Strait Of Juan De Fuca-East Entrance U.S. Waters Strait Of Juan De Fuca. Small Craft Advisory until 9 PM PDT this evening for Admiralty Inlet-Puget Sound and Hood Canal.&&$$