Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA
Issued by NWS Seattle/Tacoma, WA
400 FXUS66 KSEW 261530 AFDSEW Area Forecast Discussion National Weather Service Seattle WA 830 AM PDT Wed Jun 26 2024 .UPDATE...Quick update to add thunderstorm mention this morning along the Cascade crest. Mid-level instability remains a bit stronger than expected and the leading moisture is producing clusters of isolated thunderstorms near the Cascades from south to north this morning. Expect this trend to continue with gusty winds and lightning as the predominant threat from these storms. Meanwhile, more widespread precipitation continues to move east into the Olympic Peninsula this morning ahead of the approaching front. Cullen && .SYNOPSIS...A shift in the pattern will bring the next upper trough 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. The cycle then repeats with dry and warmer conditions Friday ahead of the next disturbance that reaches the area over the weekend. && .SHORT TERM /TODAY THROUGH FRIDAY/...A pattern change brings cooler and wetter weather back to western WA as an upper level low moves through the Pac NW. For today, showers will be mostly concentrated along the coast and in the mountains with just isolated to scattered coverage in the interior. The air mass is most unstable along the Cascade crest and there is a chance of thunderstorms too, especially in the North Cascades. We`re in post-frontal onshore flow tonight with ongoing showers and a convergence zone over the north sound. Winds will be gusty in the central interior and south sound in the 20-30 MPH range. With the cooler air mass in place, temps will drop a few degrees cooler than average with highs in the 60s along the coast and near 70 in the interior. Onshore flow continues into Thursday as the upper low shifts slowly E/NE toward southern Alberta. For western WA, plenty more showers, especially over the coast and mountains, as the low level air mass remains moist. Convergence zone showers will continue too, focused along the King/Snohomish line. Temperatures will continue to trend below average with highs in the 60s. High pressure rebuilds over the region on Friday as the upper low departs. 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 into Saturday. Wetter weather returns again Saturday night and Sunday as the ridge shifts east and a trough rotates through western WA. Weak high pressure nudges inland early next week with a few light showers mainly over the coast and mountains. 33 && .AVIATION...South-southwesterly flow aloft this morning as an upper level trough approaches W WA along with a associated cold front at the surface. Mid and high level clouds continue to stream into the region ahead of the aforementioned front and radar this morning shows widespread precipitation gradually making its way inland along the coast. Thunderstorms have also started to move up from the south along the Cascade crest this morning and will continue to make their way northward over the next few hours. Current conditions at the majority of the TAF sites remains VFR this morning, with .MARINE... the exception of MVFR conditions at KHQM as rain starts to move in. Ceilings along the coast and southwest interior have already started to lower, but expect overall ceilings across the interior to gradually lower through the afternoon and evening as the front crosses over the area. Latest guidance suggests ceilings lowering to MVFR across the interior terminals after 00z. A few localized pockets of IFR to LIFR will be possible in any heavier showers. Expect lower ceilings to continue across the region through the evening and into most of the overnight hours as showers persist throughout the area. Winds have transitioned back to the S/SW and will increase to around 12 to 17 knots, with gusts up to 20 to 25 knots possible throughout the afternoon. Winds will start to gradually ease up to 8 to 12 knots around 04z-06z. KSEA...VFR conditions will continue through the first part of the day. Winds have transitioned to S/SW this morning and will increase to around 12 to 16 knots between 15-18z. Gusts around 20 to 25 knots will be possible at times through the afternoon. Rain showers will start to move through the terminal 04z-06z with ceilings expected to lower to MVFR through the overnight period. Maz/Borth && .MARINE...A frontal system will move through the area waters this morning and into the afternoon, with breezy south-southwesterly winds throughout the interior waters. Guidance still shows small craft advisory strength westerlies through the Strait of Juan De Fuca this morning through the afternoon, maintaining around 20 to 30 kts. Southerlies will also increase throughout the Puget Sound waters this afternoon (15 to 25 kts) before gradually decreasing into the evening as the front passes through. Weak high pressure looks to build offshore briefly throughout the end of the week, with diurnal pushes down the Strait likely at times. Additional systems look to push through the area waters through the weekend and into the first part of next week. Coastal seas 3 to 5 feet this morning will generally maintain through 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. && $$