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 /TODAY THROUGH SUNDAY/

Latest satellite imagery shows marine clouds pushing eastward, getting as far west as Shelton...although for the northern half of the Olympic Peninsula, eastward progress has been far more limited to just the immediate coastline. Current temps showing a degree or two lower than 24 hours ago, seeing at least some slight influence from surface flow turning more onshore. That said, while the majority of the CWA seeing temps in the 50s, 60s are hanging on along the metro areas along the I-5 corridor, including Everett, Seattle, Tacoma and Olympia.

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 THURSDAY/

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

Onshore flow will increase in the TAF forecast as a thermal trough pushes east, with higher pressure towards the water. Flow aloft will remain westerly with a ridge breaking down to the east. Satellite this morning shows two well pronounced marine pushes in progress - one through the Strait of Juan de Fuca and another through the southwest interior approaching KSHN as of 09Z. Confidence remains low in inland track into Puget Sound terminals this morning, but in a worst case (10-20%), KPAE would be the terminal to see brief vis/cig reductions in Puget Sound. Remaining terminals west of Puget Sound and around the Olympics will continue to see ceiling and/or visibility reductions down to IFR/LIFR (including areas of fog along the coast) this morning, before retreating to the coast later this morning. Outside of the marine push, remaining terminals will see VFR conditions today with smoke continuing to clear out. Southwest winds this morning at 5 kt or less will shift to the northwest this afternoon and evening 5-10 kt, becoming light/variable tonight. Early indications for Saturday morning is another marine push staying west of Puget Sound.

KSEA...VFR conditions anticipated to continue through the TAF period with smoke clearing, and this morning's marine push likely remaining to the north/west of terminal (only a 15-20% chance of reduced visibilities in a worst-case scenario). Winds this morning will shift to the southwest at 5 kt, then switch to the northwest briefly from 02Z-06Z before returning to the southwest under 5 kt.

HPR

MARINE

High pressure will remain predominant over the waters this weekend into next week, as the thermal trough departs to the east. There has been observations of fog/mist for portions of the northern coastal waters and central/west Strait of Juan de Fuca, where a dense fog advisory has been issued through 11 AM for visibilities of 1 NM or less. Pushes of wind through the Strait of Juan de Fuca will begin this evening, with a 40-50% chance of wind gusts over 20 kt. Probabilities increase this weekend going into next week for winds over 20 kt in the strait. A couple weak troughs and a front will pass by later this weekend/early next week, which will also introduce some chances for portions of the coastal waters seeing wind gusts over 20 kt (as well as the strait). A more substantial trough/front may pass over the waters midweek next week.

Seas 3-6 ft today through Saturday, increasing to 5-7 ft briefly Sunday before dropping back to 4-6 ft Monday through next week.

HPR

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. 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.

Even though onshore flow is expected to reach deeper into the CWA today it will not be strong enough to completely alleviate concerns. As it increases in strength Saturday 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...Dense Fog Advisory until 11 AM PDT this morning for Central U.S. Waters Strait Of Juan De Fuca-Coastal Waters From Cape Flattery To James Island Out 10 Nm-Coastal Waters From James Island To Point Grenville Out 10 Nm-West Entrance U.S. Waters Strait Of Juan De Fuca.