textproduct: Seattle/Tacoma

SYNOPSIS

A thermal trough will continue to move inland today, promoting warmer temperatures across the inland lowlands. Onshore flow will return on Friday, bringing more seasonable and dry conditions with morning clouds through the weekend and potentially into early next week. Light rain is possible on Monday, with a potential pattern change on tap by the end of next week.

SHORT TERM /TONIGHT THROUGH SATURDAY NIGHT/

As an upper level ridge continues to nudge into the Pacific Northwest, a thermal trough will continue to shift inland today bringing the warmest temperatures of the week over the interior. High temperatures are on track to peak in the mid to upper 70s today, with some areas in the Cascade valleys and foothills and south of the Puget Sound reaching the low 80s. As the thermal trough progresses further inland, onshore flow will resume, bringing a more fall-like weather pattern to the region.

Onshore flow will continue through Saturday as a ridge of high pressure gradually shifts eastward. This will bring a more seasonable pattern to western Washington, with daily low stratus expanding inland and eroding by the afternoon and highs in the low to mid 70s for the lowlands. Areas along the coastline may not break out of stratus depending on the strength of the marine push each morning, with highs in the mid to upper 60s each day.

LONG TERM /SUNDAY THROUGH THURSDAY/

Sunday will bring more of the same, as southwest flow aloft continues to promote onshore flow at the surface. Mostly dry conditions may even continue into the middle of next week, as a series of systems move inland to the north over British Columbia. Ensembles continue to show chances for light precipitation in western Washington on Monday, but confidence is low. Towards the end of the week, potential increases for a pattern change that could bring cooler temperatures and widespread chances for precipitation to the region.

15

AVIATION

Light and variable flow aloft turning northerly later this evening as an upper-ridge builds into the region. VFR area wide. Low-level flow will turn onshore tonight as a push of marine stratus and areas of fog is in the offing (LIFR/IFR). The activity will start along the coast by 04-06z Friday and spread towards the inland terminals between 08-14z. Any lingering stratus should burn off to a return of VFR by 20-21z but will remain stubborn along the coast. More low stratus again likely early Saturday morning.

KSEA...VFR at the terminal throughout the evening. Surface winds W/NW 5 to 10 knots today. Winds will back to light southerly after 06Z tonight. Low IFR stratus looks to arrive around 12-14z Friday morning but should burn off by 19-20z to VFR. More low stratus again a possibility early Saturday morning.

41

MARINE

Thermally induced low pressure along the coast is shifting inland this afternoon. As a result, northerly or weak offshore flow will turn onshore tonight. Light onshore flow will then persist Friday through the upcoming weekend as a series of systems pass well north of the waters. The trend will likely persist into early next week. Seas generally 4 to 6 ft with 7 ft waves possible for the outer waters throughout this time.

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FIRE WEATHER

A thermal trough pushing inland today will bring one last day of warmer and drier conditions throughout the interior. Offshore flow will gradually transition back to onshore this afternoon, though relative humidity values still look to dip into the 20s and 30s across portions of the Cascades, with the lowest humidities concentrated over the North Cascades.

Onshore flow will then bring cooler temperatures and increased moisture to the area Friday through the weekend, helping to minimize fire weather concerns into early next week.

14/Mazurkiewicz

SEW WATCHES/WARNINGS/ADVISORIES

WA...None. PZ...None.