textproduct: Seattle/Tacoma

SYNOPSIS

An upper level trough will maintain cooler temperatures, cloudy skies, and chances for sprinkles through Tuesday. A ridge builds over the region mid-week, bringing a drying and warming trend. Near normal temperatures and partly cloudy conditions are expected to return through the weekend with continued low level onshore flow.

SHORT TERM /TODAY THROUGH WEDNESDAY NIGHT/

Northwest flow aloft this afternoon will continue to promote onshore flow, cloudy skies, and cooler temperatures throughout the day. High temperatures will peak several degrees below normal across the lowlands, in the mid to upper 60s for most areas. An upper level trough will pass over the Pacific Northwest through the day on Tuesday, bringing chances for light rain mainly over the Cascades and lowlands east of the Puget Sound in the morning with showers tapering off over the mountains in the afternoon. As the weather system progresses to the south Tuesday afternoon, skies will slowly break up with plenty of sun breaks by the late afternoon.

High pressure will continue to build over the region late Tuesday, with mostly clear skies and residual moisture allowing for patchy fog to develop early Wednesday morning. The fog and low stratus will burn off by the late morning, revealing clear skies and calm conditions. Temperatures Wednesday will peak right around normal for early fall, with highs mostly in the low to mid 70s.

LONG TERM /THURSDAY THROUGH SUNDAY/

Warming will continue into Thursday as a thermal trough develops along the coast and flow briefly turns weakly offshore early Thursday morning. The thermal trough will shift inland during the day Thursday, bringing high temperatures into the mid to upper 70s, with some spots south of the Olympics and along the Cascade valleys hitting 80 degrees. Onshore flow will return by Friday and continue to varying degrees through the weekend, with temperatures returning to near-normal and periodic marine low stratus that is expected to remain west of the Puget Sound each morning.

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AVIATION

There is broad upper level troughing over the Pac NW tonight into Tuesday with light onshore flow near the surface. Ceilings are VFR but may see patchy low clouds or fog around the south sound overnight. The trough may generate a few light showers and brief MVFR cigs in the interior Tuesday morning. Dry, north flow will follow Tuesday afternoon and evening with a return to VFR conditions.

KSEA...VFR rest of today and overnight with a switch to light N winds around 06z. Patchy low clouds may form around 18z as a trough moves through. Drier weather and VFR moving forward through Tuesday afternoon and evening.

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MARINE

Weak onshore flow tonight with the flow turning more northerly on Tuesday. Offshore flow will develop Wednesday and Thursday as a thermal trough forms along the coast. Onshore flow returns Friday and into the weekend.

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FIRE WEATHER

Minimal fire weather concerns through next week. A weak weather system will move through the area on Tuesday, bringing the chance for light precipitation. A drier and warmer pattern Wednesday into Thursday. Surface winds will briefly transition offshore late Tuesday into Wednesday morning, decreasing minimum RH values toward the mid 20s to low 30s, especially in the north Cascades. Minimum relative humidity values rebound on Friday as onshore flow returns and continues into next week.

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SEW WATCHES/WARNINGS/ADVISORIES

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