textproduct: Seattle/Tacoma

SYNOPSIS

Upper level low over Eastern Oregon combined with upper level ridge over Central British Columbia giving Western Washington dry northeasterly flow aloft through Monday. The ridge will move over Western Washington Tuesday. Atmospheric river moving inland north of the area Tuesday night and Wednesday. Upper level ridge building Thursday will move east Friday. Low level offshore flow Thursday and Friday producing above normal high temperatures. Next system possibility moving into the area Friday night into Saturday.

SHORT TERM /TODAY THROUGH TUESDAY/

Satellite imagery shows mostly clear skies with a patch of stratus from about Renton to Everett. Folks over Northern Washington got a good view of the aurora between midnight and 2 am. Temperatures at 3 am/10z were in the mid 30s to near 50.

Light flow in the lower levels this morning with patchy fog developing before sunrise. The stratus and patchy fog will dissipate by mid morning leaving sunny skies over the area. High temperatures near normal, upper 50s to mid 60s.

Little change in the pattern tonight into Monday with dry northeasterly flow aloft and light flow in the lower levels. Monday morning will be the coldest morning since May with lows in the 30s and lower 40s. A frost advisory has already been issued for most of the area south of Seattle plus the Hood Canal and North Coast. Plenty of sunshine Monday with highs again in the upper 50s to mid 60s.

Upper level ridge to the north moving over Western Washington Monday night into Tuesday. Slight increase in onshore flow overnight plus some high clouds keeping lows in the mid 30s to mid 40s. High clouds remaining over the area during the day Tuesday with highs in the mid 50s to mid 60s. Cooler high temperatures to the north with thicker high cloud cover. Felton

LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/

Atmospheric river aimed at Vancouver Island and Central British Columbia Tuesday night into Wednesday. Slight chance of rain along the coast and near the Canadian border. Lows in the 40s and highs in the 60s.

Models in good agreement with a strong upper level ridge building Wednesday night and Thursday. 500 mb heights in the mid to upper 580 dms by Thursday night. Low level flow turning offshore warming highs into the 60s and lower 70s. Lows remaining in the 40s.

Upper level ridge moving off to the east Friday with low level offshore flow continuing. Friday looks to be the warmest day with highs in the mid 60s to mid 70s. No records expected Friday with October 16th in 2022 being one of the warmest October days on record ( Seattle high that day was 88, the second warmest October day ). Lows in the 40s and lower 50s.

Upper level ridge well to the east by Friday night. This opens the door for a weakening warm front to possibly reach the area Friday night into Saturday. For now just chance or slight chance pops. Highs much cooler, in the lower to mid 60s. Felton

AVIATION

Northeast flow aloft continues over Western Washington today as the region remains between an upper trough east of the Cascades and an upper ridge centered well offshore. Low level moisture and light surface winds have led to areas of LIFR conditions in fog and low clouds around Lake Washington as well as outlying river valleys. Low clouds will lift and scatter by around 18Z. VFR is expected areawide this afternoon with valley fog and low clouds reforming again tonight.

KSEA...Valley fog is forming east of the terminal this morning. The general expectation is that it will not impact the terminal directly, but it will be in the vicinity through 18Z or so. Otherwise, VFR is expected through the day ahead. Surface winds light E/NE this morning will become northerly and rise to 7 to 11 knots this afternoon.

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MARINE

High pressure over the interior of British Columbia will lead to northerly or weak offshore flow today. The ridge over interior British Columbia will weaken tonight for light winds across area waters. A weak frontal system will move across the waters late Tuesday night into Wednesday. High pressure rebuilds across the area on Thursday with offshore flow developing. Seas are expected to remain below 10 feet across the coastal waters through the period.

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SEW WATCHES/WARNINGS/ADVISORIES

WA...Frost Advisory until 8 AM PDT this morning for Foothills and Valleys of Pierce and Southern King Counties-Foothills and Valleys of Thurston and Lewis Counties-Middle Chehalis River Valley.

Frost Advisory from midnight tonight to 8 AM PDT Monday for Eastern Kitsap County-Foothills and Valleys of Pierce and Southern King Counties-Foothills and Valleys of Thurston and Lewis Counties-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-Middle Chehalis River Valley-Northern Hood Canal-Northern Washington Coast-Olympia and Southern Puget Sound-Southern Hood Canal-Willapa and Black Hills.

PZ...None.