textproduct: Seattle/Tacoma

SYNOPSIS

Zonal flow aloft into Friday with precipitation chances along the northern portions of Western Washington. Warm, dry conditions over the weekend as an upper ridge builds over the Pacific Northwest. Onshore flow returns early next week with the return of near normal temperatures but continued dry conditions.

SHORT TERM /TONIGHT THROUGH SATURDAY NIGHT/

Westerly flow aloft continues into Friday with a building upper level ridge across the majority of the Western US. A weakening weather system will move across the northern periphery of the ridge into BC into Friday, resulting in continued mid and high clouds at times. Although the majority of precipitation will remain in BC, light rain at times may occur along the northern Olympic Peninsula and Whatcom and San Juan Counties into midday Friday. Otherwise, temperatures remain near to slightly above normal through Friday.

The upper ridge builds further across Western Washington Friday night into the weekend resulting in dry conditions and warming temperatures. Stratus and areas of fog are expected Saturday morning around Puget Sound with relatively light north winds. Clouds will clear for sunny conditions in the afternoon. Temperatures Saturday will peak in the mid 60s to mid 70s, and even in the low 80s in the Cascade Valleys under light offshore flow.

LONG TERM /SUNDAY THROUGH THURSDAY/

The upper ridge will remain in place over the majority of the Western US on Sunday, resulting in temperatures being a few degrees warmer by Sunday afternoon, and continued dry conditions. Ensembles are consistent in the ridge beginning to flatten over Western Washington on Monday, with onshore flow returning, and a slight cooling trend in temperatures along with increasing morning stratus. Dry conditions are expected into midweek though with a continued ridging influence. JD

AVIATION

Widespread VFR conditions this evening, with light rain at KBLI as a front passes to the north. IFR to MVFR cigs will be redeveloping along the coast with weak onshore flow. Marine stratus may intrude inland as far as Shelton, but is unlikely to progress east of the Kitsap Peninsula. Clear skies and light winds will preempt some possible FG development in the south Puget Sound, namely KOLM. Winds will be WSW throughout most of the TAF period, becoming northerly tomorrow afternoon.

KSEA...VFR will persist throughout the night, with light WSW flow. The probabilities for stratus getting east of Puget Sound into the terminal are still low, 20% or less, but have opted to retain the SCT 007 in the TAF between 13Z-17Z. SSW winds will turn northerly after 00Z Saturday at 4-7 kts.

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MARINE

High pressure continues across the waters this week. A weak front will move north of the area into Friday, but little in the way of wind or wave impacts are expected. A thermal trough will build along the coast on Saturday bringing northerly to offshore winds to the waters Saturday and Sunday. Onshore flow returns late Monday with a westerly push through the Strait of Juan de Fuca Monday evening. Generally light flow then returns into midweek. Seas are expected to remain between 4 to 6 feet through early next week. JD

FIRE WEATHER

Fire weather concerns remain minimal through the next few days. Developing high pressure aloft this weekend with a thermal trough building up the coastline will bring warm temperatures and light offshore flow. This could result in locations in the Cascades and adjacent valleys seeing minimum RH values approach 30% on Sunday. This will be short lived, with onshore flow returning early next week to boost humidity values and bring back cooler temperatures.

SEW WATCHES/WARNINGS/ADVISORIES

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