textproduct: Seattle/Tacoma

SYNOPSIS

Warm conditions today will be followed by a gradual cooldown over the weekend to near-normal temperatures. The backside of an upper level ridge will remain over Western Washington through Saturday. Upper level flow becomes zonal on Sunday, continuing through at least the first part of the week. Uncertainty in the forecast increases towards the second part of the week.

SHORT TERM /TONIGHT THROUGH SUNDAY NIGHT/

Cooler temperatures this afternoon west of the I-5 corridor. Locations near the coast seeing temperatures in the mid 60s, while more interior locations seeing temperatures in the mid 70s/low 80s. As for east of the I-5 corridor, warmer temperatures in the mid 80s to low 90s.

The backside of the upper level ridge that moved over the area this week will begin to gradually flatten tonight. Although the ridge flattens, heights will remain slightly elevated over the area remain over the area and will start to gradually decrease later on Saturday. This will lead to a gradual cooldown for Western Washington this weekend with temperatures expected to moderate to near-normal this weekend.

Stronger onshore flow will have the marine layer push further inland Saturday morning. Expect cloudy skies in the morning and then mostly clear skies in the afternoon. High temperatures on Saturday will be in the upper 60s/low 70s for the coast and mid 70s/low 80s for the interior. Slightly cooler Sunday with high temperatures in the 60s along the coast and mid to upper 70s in the interior. Low temperatures will be in the 50s.

Wildfire smoke conditions have improved toward the coast and will continue to improve across the interior and mountains this evening. Some elevated smoke may not completely clear out until early Saturday morning.

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LONG TERM /MONDAY THROUGH FRIDAY/

Zonal flow is favored to continue through at least the first part of the week with temperatures near-normal. Past the middle of the week, long-term guidance continues to struggle with the upper level pattern. Solutions are split whether zonal flow will linger into Wednesday or if a ridge or weak trough will take its place. As for the second part of the week, solutions are evenly split on whether the area will be under the influence of a ridge or trough.

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AVIATION

A upper level ridge remains over the region today with west to southwest flow aloft. Low level onshore flow is increasing near the surface. Stratus remains along the immediate coastline this afternoon with hazy VFR conditions for the interior as some wildfire smoke lingers over the area. Coastal stratus will make a further inland intrusion late tonight into Saturday morning with a brief period of IFR stratus expected at terminals around Puget Sound. VFR will return for interior locations again by around 16Z-18Z Saturday.

KSEA...VFR with haze today. Increasing onshore flow makes IFR stratus more likely for the terminal 13Z-17Z on Saturday. Surface winds SW 5 to 8 knots will veer W/NW 7 knots or less for a period late this afternoon. Winds will back to S/SW again tonight.

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MARINE

Broad surface ridging will remain centered over the offshore waters with lower pressure east of the Cascades into early next week maintaining onshore flow. This will lead to daily diurnally driven small craft advisory strength westerlies in the central/east strait. A series of weak systems passing north of the area early next week will strengthen onshore flow for a low end risk of gales in the central/east strait.

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FIRE WEATHER

Elevated fire weather conditions across the Cascades this afternoon with above average temperatures in concert with dry conditions. Minimum RHs have fallen into the mid 10s to lower 20s in some areas of Cascade zones 658/659. While no significant wind or instability is expected in the near term, and thus no need for any fire weather headlines, given the persistent warm and dry conditions continued caution is highly encouraged.

Onshore flow will strengthen later this evening as a stronger push of marine air enters western Washington. Very isolated areas of 20- 25% min RHs are possible in the Cascade valleys on Saturday but widespread concerns are not expected - alleviating the threat for elevated fire weather concerns. More benign fire weather conditions will emerge on Sunday and lead into into the middle next week. Cooler temperatures and increased moisture with much better humidity recoveries are expected across the region.

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SEW WATCHES/WARNINGS/ADVISORIES

WA...Heat Advisory until 10 PM PDT this evening 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.

PZ...Small Craft Advisory until 3 AM PDT Saturday for Central U.S. Waters Strait Of Juan De Fuca-East Entrance U.S. Waters Strait Of Juan De Fuca.