textproduct: Seattle/Tacoma

SYNOPSIS

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

SHORT TERM /TONIGHT THROUGH SUNDAY/

Latest satellite imagery shows this morning's marine layer starting to slowly retreat back to the coast. Locations under the influence of the marine layer much cooler this morning with temperatures in the upper 50s/low 60s. Whereas, locations east of the I-5 corridor already seeing temperatures reaching into the low 70s.

The upper ridge will shift eastward throughout the day today. This, along with the aforementioned onshore flow and the slightly cooler temperatures early this morning will ease HeatRisk concerns for much of the area. However, also stated above, the warmer conditions along the I-5 corridor suggests that there will be one more day of Moderate/Orange HeatRisk there. As such, inherited Heat Advisory will remain in place. Continued onshore flow will continue to erode smoke concerns, but similar to HeatRisk, conditions will still allow for some haze again today before more successful eastward progress of marine air should limit smoke concerns to the Cascades and locations near any burning wildfires.

Zonal flow will keep conditions over the CWA pretty uneventful for the remainder of the near term. Daytime highs will ease a couple of degrees each day with Saturday mostly in the mid to upper 70s /except for the lower 80s along the I-5 corridor and SW interior/ and more widespread mid to upper 70s for Sunday /mid to upper 60s along the coast/.

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LONG TERM /SUNDAY NIGHT THROUGH FRIDAY/

Long-term guidance keeps zonal flow aloft in place through at least Wednesday...perhaps extending into early Thursday. It is at midweek where dissolution of the consensus occurs, where there are some hints at a potential weak trough. Solutions vary though, with some bringing this feature one Wednesday, others on Thursday and various times in between. Regardless, this trough looks to be mainly a dry feature. High temps throughout the long term look to remain static from where they were at the conclusion of the short term, with mid to upper 70s expected for the interior lowlands while locations along the coast or water adjacent can expect persistent mid to upper 60s.

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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. IFR/LIFR stratus extending locally inland will retreat to 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 for a brief period of IFR stratus 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 likely for the terminal 13Z-17Z on Saturday. Surface winds S/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 risk of gales in the central/east strait.

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FIRE WEATHER

Elevated fire weather conditions across the area today 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. Onshore flow made it to the Olympics last night - and with an additional round setting up this afternoon concerns for fire weather are waning for the mountains there. 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.

As mentioned, onshore flow will kick into gear 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. More benign fire weather conditions will emerge on Sunday and lead into into early 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...None.