textproduct: Seattle/Tacoma

SYNOPSIS

Dry northerly flow aloft today with upper level low over Southeast Oregon and upper level ridge over Southern British Columbia. Ridge moving over Western Washington tonight will weaken Tuesday as an atmospheric river moves into Southern British Columbia. The ridge will rebuild over the area Wednesday and Thursday then shift east Friday. Low level offshore flow Thursday and Friday for a couple of warm days. Weakening system moving into Western Washington Friday night and Saturday with another system possible Sunday night.

SHORT TERM /TODAY THROUGH WEDNESDAY/

Satellite imagery shows clear skies over Western Washington this morning with fog in the Snohomish and Lower Chehalis river valleys. It's a brisk fall morning with temperatures at 3 am/10z ranging from near freezing at Shelton and Olympia to the mid 40s in the Seattle metro area. Seattle Tacoma airport at 44 degrees. The last time Seattle had a low in the 30s was April 16th ( 36 degrees ).

Sunny today with dry northerly flow aloft over the area. Morning valley fog will not last more than a couple of hours after sunrise. Frost advisory for most locations south of Seattle and along the north coast will expire at 8 am/15z. Highs near normal, in the upper 50s to mid 60s.

Upper level ridge over British Columbia today moving south over Western Washington tonight. Atmospheric river approaching British Columbia spreading high clouds over the area. This will keep low temperatures a little warmer Tuesday morning, in the mid 30s to mid 40s.

High clouds continuing into Tuesday with the atmospheric river moving into the Central British Columbia coast. Upper level ridge over the area weakening Tuesday night with the atmospheric river sagging slightly south putting the north coast and the Northwest Interior on the very southern edge of the river. Likely pops along the north coast with chance pops over the Northwest Interior. Highs Tuesday in the mid 50s to mid 60s with the colder highs to the north with the thicker cloud cover. Lows Tuesday night in the 40s.

Upper level ridge rebuilding over Western Washington Wednesday with the 500 mb heights near 580 dms by 00z Thursday. Chance of rain coast and north of Seattle in the morning. Atmospheric river dissipating by afternoon making for a mostly cloudy to cloudy day. Highs in the lower to mid 60s. Felton

LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/

Models in good agreement with the upper level ridge continuing to build over the area Wednesday night and Thursday. 500 mb heights in the mid 580s dms by Thursday afternoon. Low level flow turning offshore Thursday warming highs into the mid 60s to lower 70s.

Upper level ridge shifts east Thursday night into Friday but low level offshore flow continuing at least through Friday morning. Friday looks to be the warmest day of the week with highs in the mid 60s to mid 70s. Even with highs over 10 degrees above normal Friday ( Seattle normal high 60 degrees ) not expecting any records as October 16th back in 2022 was one of the hottest October days on record ( the high in Seattle was 88 degrees ).

Upper level ridge well to the east Friday night and Saturday with a dissipating system moving into the area. Best chances for rain north coast and North Cascades. A stronger more organized system will approach the coast Sunday. Highs cooling to the lower to mid 60s Saturday and mid 50s to lower 60s Sunday. Lows in the 40s for the most part through the period with lower 50s possible in the Seattle metro area. Felton

MARINE

Weak pressure gradients will produce little in the way of wind across area waters today. A weak surface ridge will shift inland on Tuesday as a frontal system approaches the offshore waters with winds shifting to the E/SE across much of the waters. A weak cold front will reach the area on Wednesday with possible headlines for low end small craft advisory winds across portions of the coastal waters and the west entrance to the strait. High pressure rebuilds across the waters on Thursday with the flow turning northerly or weakly offshore as thermally induced low pressure expands northward across Western Oregon. Another front is expected to reach the waters Friday night or Saturday with possible headlines for winds and/or steepening seas across the coastal waters.

27

SEW WATCHES/WARNINGS/ADVISORIES

WA...Frost Advisory until 8 AM PDT this morning 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.