textproduct: Seattle/Tacoma

SYNOPSIS

Warm conditions through Friday, followed by a gradual cooldown to near-normal temperatures by the end of the week. Upper level ridge axis and thermally induced trough over Western Washington today will push east tonight. The backside of the ridge will remain over the region through Saturday. Upper level flow becomes zonal on Sunday, continuing through at least midweek. Uncertainty in the forecast towards the second part of the week.

SHORT TERM /TONIGHT THROUGH SATURDAY NIGHT/

Another warm and smoky day for Western Washington. Latest obs show temperatures in the mid/upper 80s to low 90s along the interior and 70s along the coast. Visibilities range between 5 to 9 miles.

The ridge axis over Western Washington will move into Eastern Washington tonight, along with the thermal trough. A gradual cooldown expected to start Friday as the back end of the ridge moves across the area through Saturday. However, temperatures will remain slightly elevated east of the I-5 corridor for the interior and foothills. Low temperatures in the upper 50s to low 60s and high temperatures will be in the mid/upper 80s to low 90s will have Moderate HeatRisk for these locations. Consequently the heat advisory has been extended through Friday night. As for locations west of I-5, onshore flow will help cool temperatures into the upper 60s to low 70s for the coast and low to mid 80s for interior locations.

With the thermal trough having pushed east, onshore flow will help gradually mitigate smoke impacts tonight through Friday for the interior portions. However, some elevated some may not completely clear out until later Friday or early Saturday.

LONG TERM /SUNDAY THROUGH THURSDAY/

Long-term guidance favors zonal flow aloft to establish over Western Washington through at least early next week. By midweek solutions begin to disagree on the forecast. Although, majority of members continue to trend toward zonal flow on Wednesday. As for Thursday, some solutions hint at an upper level ridge forming over Western Washington, while other solutions favor a weak trough over the region.

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AVIATION

VFR cigs with visibility impacts from smoke this afternoon. Onshore flow will continue to mitigate smoke impacts near the surface tonight and into tomorrow. Slant-wise visibility impacts should also gradually improve this afternoon into tomorrow as smoke aloft disperses. Another marine push expected tonight, bringing IFR/LIFR conditions to the coast and portions of the southwest interior towards SHN. Latest guidance suggests the stratus will attempt to push east towards the Kitsap Peninsula and OLM, keeping a slight chance(30%)for MVFR cigs overnight. Brief improvement along the coast in the afternoon, before conditions deteriorate again in the evening. Generally NW winds 4-6 kt will become light to calm overnight at interior terminals. Winds shift SW Friday morning.

KSEA...VFR conditions will prevail today and Friday. Wildfire smoke continues to impact surface visibility to around 6SM. Smoke conditions at the surface and aloft should gradually improve tonight into tomorrow with onshore flow. NW winds this afternoon 4-6 kt, becoming light overnight. Winds shift SW Friday morning and increase to 5-7 kt in the afternoon.

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MARINE

An area of strong high pressure will continue to strengthen over the NE Pacific and expand into Washington's waters. It will remain over area waters into early next week. Increasing onshore flow will lead to diurnal pushes likely (70-90% chance) meeting small craft thresholds through the Strait of Juan de Fuca each evening starting on Friday. Guidance continues to back off the potential (15% chance) for gales on Saturday; rather guidance is suggesting a high-end small craft event. In addition, there is a 20-30% chance for gales on Tuesday through the Strait of Juan de Fuca. Headlines also possible this weekend for the coastal waters. Winds will increase across the coastal waters starting Saturday, bringing a 40-70% chance for small craft winds to the southernmost zones. Seas will also be steep this Saturday with combined seas of 6-8 feet and a dominant period around 7 seconds.

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FIRE WEATHER

Elevated fire weather conditions across the area today and tomorrow with above average temperatures in concert with dry conditions. Minimum RH values are lowering into the mid 10s to lower 20s in Cascade zones 658/659 and surrounding valleys. Olympic zones 661 and 652 zones have seen their lowest RHs earlier this morning with values in the 20s for location such as Hurricane Ridge. While no significant wind or instability is expected today for a red flag warning, maximum caution over new fire starts still should be emphasized.

The thermally induced trough is currently shifting eastward. As a result, a gentle push of onshore flow is expected this evening into Friday but not strong enough to completely alleviate concerns. Onshore flow will increase in strength Saturday into into early next week with cooler temperatures and increased moisture with much better humidity recoveries across the region.

Wildfire smoke over the area today could cause localized impacts to fire operations.

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SEW WATCHES/WARNINGS/ADVISORIES

WA...Heat Advisory until 10 PM PDT this evening for Eastern Kitsap County-Eastern Strait of Juan de Fuca-Foothills and Valleys of Thurston and Lewis Counties-Foothills of the Western and Southern Olympic Peninsula-Island County-Lake Crescent Area Including US 101-Lower Chehalis River Valley-Lowlands of Lewis and Southern Thurston Counties- Middle Chehalis River Valley-Northern Hood Canal-Olympia and Southern Puget Sound-Port Townsend Area-San Juan County-Southern Hood Canal-Willapa and Black Hills.

Air Quality Alert until 5 PM PDT this afternoon for Cascades of Whatcom and Skagit Counties-Foothills of the Western and Southern Olympic Peninsula-Grays Harbor County Coast- Lower Chehalis River Valley-Lowlands of Western Whatcom County-Middle Chehalis River Valley-Olympia and Southern Puget Sound-Olympics-Southern Hood Canal.

Air Quality Alert until 8 AM PDT Friday for Cascades of Pierce and Lewis Counties-Cascades of Snohomish and Northern King Counties-Cascades of Southern King County-City of Seattle-Downtown Everett / Marysville Area-Eastern Kitsap County-Eastside-Foothills and Valleys of Central King County-Foothills and Valleys of Pierce and Southern King Counties-Foothills and Valleys of Snohomish and Northern King Counties-Foothills and Valleys of the North Cascades- Lowlands of Pierce and Southern King Counties-Lowlands of Western Skagit and Northwestern Snohomish Counties- Northern Hood Canal-Shoreline / Lynnwood / South Everett Area.

Heat Advisory until 10 PM PDT Friday for City of Seattle- Downtown Everett / Marysville Area-Eastside-Foothills and Valleys of Central King County-Foothills and Valleys of Pierce and Southern King Counties-Foothills and Valleys of Snohomish and Northern King Counties-Foothills and Valleys of the North Cascades-Lowlands of Pierce and Southern King Counties-Lowlands of Western Skagit and Northwestern Snohomish Counties-Lowlands of Western Whatcom County-Shoreline / Lynnwood / South Everett Area.

Air Quality Alert until 11 PM PDT this evening for Foothills and Valleys of Thurston and Lewis Counties-Lowlands of Lewis and Southern Thurston Counties-Willapa and Black Hills.

PZ...None.