textproduct: Seattle/Tacoma

SYNOPSIS

Upper level ridge centered well to the southeast extending back over Western Washington through Wednesday. Southwesterly flow aloft with high clouds moving through at times. In the lower levels light flow with a thermally induced surface trough bouncing back and forth between the coast and the interior. Pattern change Wednesday night into Thursday with the remnants of tropical storm Elida moving through producing a chance of showers. Upper level trough over Western Washington with low level onshore flow Friday through the weekend for a round of seasonable temperatures.

SHORT TERM /TODAY THROUGH WEDNESDAY/

Satellite imagery shows high clouds embedded in the southwesterly flow aloft over the area this morning with low stratus along the coast. Mild temperatures at 3 am with the cloud cover, mostly in the mid 50s to mid 60s.

The combination of the high clouds plus a little smoke aloft could produce a colorful sunrise this morning if the cloud cover is not too thick.

Upper level ridge centered well to the southeast extending back over Western Washington through Wednesday. 500 mb heights in the mid to upper 580 dms. In the lower levels thermally induced surface trough developing over the area today. The trough will bounce back and forth between the coast and the interior through Wednesday retreating back to the coast in the overnight hours and moving inland during the daytime. Model 850 mb temperatures in the plus 16C to plus 20C range today slowly warming to plus 22C to plus 24C Wednesday afternoon. Warming trend the next three days over the interior. Highs today in the 80s, 80s to lower 90s Tuesday and 80s to mid 90s Wednesday. Along the coast with the thermally induced surface trough drifting inland during the day highs in the mid 70s to lower 80s today and Tuesday. A little cooler Wednesday with the thermally induced trough inland, in the 70s.

A heat advisory has already been issued for Tuesday morning through Wednesday evening. In addition to the very warm daytime temperatures with high clouds moving through at times morning lows will be elevated as well, in the mid 50s to mid 60s. Probably will not set any record high minimum temperatures ( Seattle records 66 Tuesday and 68 Wednesday both set in 2006 ) but it will be close.

With the low level flow turning northerly at times this will pull down some wildfire smoke from Canada the next three days. Most of the smoke is expected to remain a bit elevated keeping air quality from deteriorating too much. The exception to this will be near the Cascade crest in the Central and Northern Cascades where overnight easterly winds could pull in thicker smoke from the fires along the east slopes of the Cascades.

Highs in Seattle forecasted to be in the 90s both Tuesday and Wednesday. This will be the first 90 degree plus days in July this year. The last time Seattle did not get at least one 90 degree plus day in July was 2017 ( there were 5 90 degree plus days in August 2017 and 2 more in September ). Before this current streak of 8 Julys in a row with at least one 90 degree plus day the longest streak was only 4 years ( 1958-1961 and 1970-1973 ). Felton

LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/

Pattern change beginning Wednesday night into Thursday as the remnants of tropical storm Elida approach the area offshore. Thursday forecast has a lot of bust potential. Ensembles still showing a few members with the moisture from Elida moving over Western Washington Thursday producing showers. More ensemble members are in the camp that this will just be some middle and high level clouds. Either way the low level flow turns onshore resulting in some cooling. Will go with a bit of a combination of the solutions dropping high temperatures 5 to 10 degrees Thursday ( weak marine push scenario ) with a slight chance of showers. Better consistency in the solutions Friday into the weekend with upper level trofiness overhead and low level onshore flow. Morning clouds and afternoon sunshine for the interior Friday through Sunday. Highs near normal, in the 70s interior and mid 60s coast. Felton

AVIATION

Southwest flow aloft is expected across Western Washington today with strong upper ridging centered over the Rockies and a weak upper trough offshore. The low level flow is light northerly or weakly offshore. LIFR stratus along the immediate coast will burn off by this afternoon. VFR conditions under varying amounts of high level clouds are expected for the remainder of the region. Increasing wildfire smoke across northwest WA may begin to limit both horizontal and slant-range visibility by this afternoon.

KSEA...VFR. Surface winds northerly 6 to 10 knots easing to light this evening.

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MARINE

High pressure will remain centered offshore with lower pressure inland through the week. Onshore gradients will ease through the early part of the week as thermally-induced low pressure develops across Western Washington and Oregon. Stronger onshore flow and pushes down the strait look to resume in the latter half of the week as the thermal trough shifts eastward.

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FIRE WEATHER

Elevated fire weather concerns the next three days with the very dry and warm conditions. Minimum relative humidity values in the 20 to 30 percent range, with drier locations in the south Sound capable of getting into the upper teens. While there is still a lot of uncertainty regarding the low pressure system off the coast from what was once tropical storm Elida, chances for thunderstorms late in the week are low at this point, but cannot be fully ruled out. Any thunderstorms that develop after another round of hot and very dry conditions pose a risk of additional ignitions from lightning. Fire weather concerns ease Friday into the weekend with cooler days and low level onshore flow. Felton

SEW WATCHES/WARNINGS/ADVISORIES

WA...Heat Advisory from 10 AM Tuesday to 11 PM PDT Wednesday for City of Seattle-Downtown Everett / Marysville Area- Eastern Kitsap County-Eastern Strait of Juan de Fuca- 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 Thurston and Lewis Counties-Foothills and Valleys of the North Cascades- Foothills of the Western and Southern Olympic Peninsula- Lake Crescent Area Including US 101-Lowlands of Lewis and Southern Thurston Counties-Lowlands of Pierce and Southern King Counties-Lowlands of Western Skagit and Northwestern Snohomish Counties-Lowlands of Western Whatcom County-Middle Chehalis River Valley-Northern Hood Canal-Olympia and Southern Puget Sound-Port Townsend Area- Shoreline / Lynnwood / South Everett Area-Southern Hood Canal.

PZ...Small Craft Advisory until 5 AM PDT early this morning for Coastal Waters From Cape Flattery To James Island 10 To 60 Nm-Coastal Waters From James Island To Point Grenville 10 To 60 Nm-Coastal Waters From Point Grenville To Cape Shoalwater 10 To 60 Nm.