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 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 first part of next week for a round of seasonable temperatures.

SHORT TERM /TODAY THROUGH THURSDAY/

Satellite imagery shows high clouds over most of the area early this morning with patchy low clouds and fog along the coast. High clouds keeping temperatures mild overnight with most places in the lower to mid 60s at 3 am/10Z.

Upper level ridge centered well to the southeast extending back over Western Washington through Wednesday. Southwesterly flow aloft sending high clouds through the area at times. Thermally induced surface trough along the coast this morning will shift inland this afternoon, retreat back to the coast tonight then move inland again Wednesday afternoon. Temperatures aloft warming with the 850 mb temperatures peaking in the plus 22C to 24C range Wednesday afternoon. All this adds up to a pair of hot days for Western Washington with near record breaking high temperatures and maximum low temperatures. Highs today in 80s to mid 90s over the interior warming a couple of degrees Wednesday into the mid 80s to near 100. Highs on the coast in the mid 70s to mid 80s both days. Lows in the lower to mid 60s inland and mid 50s along the coast.

A heat advisory will go into effect this morning at 10 am/17Z and remain in effect until at least 11 pm Wednesday evening.

In addition to the heat, northerly flow at times will pull wildfire smoke from British Columbia into Whatcom and Skagit Counties. An Air Quality Alert has been issued by the Northwest Clean Air Agency. Weak easterly flow today will also bring wildfire smoke from eastern Washington west of the crest. While incoming wildfire smoke may cause localized degradations in air quality at times over the mountains, the smoke is not expected to mix down into the lower levels and is favored to stay east of the Seattle metro.

Changes in the pattern Wednesday night into Thursday with remnants of tropical storm Elida moving through Thursday morning creating a chance of showers. In addition to the possible showers low level flow turning onshore producing much cooler high temperatures. After lows in the lower to mid 60s again Thursday morning for the interior highs cooling to the 70s and lower 80s. For the coast, lows in the mid 50s and highs in the mid 60s.

The return of low level onshore flow will get rid of any smoke concerns in the lower levels. Felton

LONG TERM /THURSDAY NIGHT THROUGH MONDAY/

Weak upper level low that is what will be left of Elida remaining offshore Thursday night through Friday night with low level onshore flow. Upper level low weakening into an upper level trough and moving through Western Washington Saturday. Another chance for showers as the trough moves through the area. Weak upper level trofiness with low level onshore flow continuing Sunday and Monday. Seasonable temperatures through the period with highs in the 60s on the coast and 70s inland. Lows in the 50s. Felton

AVIATION

High pressure will lead to dry and stable conditions across western WA today. Low clouds may clip the coast early this morning otherwise VFR conditions are expected with high clouds aloft. Wildfire smoke aloft across northwest WA may limit both horizontal and slant-range visibility at times.

KSEA...VFR today with N wind around 5 kt.

MARINE

Strong high pressure is offshore with a thermal trough along the WA coast. Overall winds are generally light across western WA with seas under 6 ft. The thermal trough will shift inland Wednesday and Thursday with strong onshore pushes expected through the strait of Juan de Fuca. 33

FIRE WEATHER

Elevated fire weather concerns the next two days with near record high temperatures and very dry conditions especially in the afternoon hours. Minimum relative humidities will fall as low as 20% to 30% both Tuesday and Wednesday, with drier locations across the southern Puget Sound potentially bottoming out in the teens. There is a very slight chance of thunderstorms coming in from the south Thursday morning which given the warm and dry conditions could cause additional ignitions from lightning. Onshore flow will increase later Thursday bringing cooler temperatures and better overnight RH recoveries through the weekend into the first part of next week easing fire weather concerns. Felton

SEW WATCHES/WARNINGS/ADVISORIES

WA...Air Quality Alert until 9 AM PDT Wednesday for Cascades of Whatcom and Skagit Counties-Foothills and Valleys of the North Cascades-Lowlands of Western Skagit and Northwestern Snohomish Counties-Lowlands of Western Whatcom County.

Heat Advisory from 10 AM this morning 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...None.