textproduct: Seattle/Tacoma

SYNOPSIS

A weather system moving into British Columbia will brush western Washington on Tuesday, bringing showers to the Pacific coast and the North Interior into Wednesday. A ridge of high pressure will rebuild over the area Wednesday into Thursday, before pushing inland on Friday. Warm temperatures are expected Thursday and Friday as offshore flow develops. A weak system will move into the area on Saturday, followed by a stronger system Sunday into Monday.

SHORT TERM /TONIGHT THROUGH WEDNESDAY NIGHT/

Satellite imagery shows sunny and clear skies across western Washington this afternoon, with areas of patchy fog this morning having dissipated. Highs are still on track to be close to seasonal norms today, and are expected to top out in the upper 50s to mid 60s across the area. Dry conditions will continue into tonight as an upper level ridge over the region flattens. A weather system moving into British Columbia tonight into Tuesday will bring increasing mid to high cloud cover to the area overnight, bringing warmer overnight low temperatures to much of western Washington and limiting the potential for fog and frost formation overnight. Overnight lows are expected to be in the upper 30s to mid 40s.

The system moving into British Columbia will brush western Washington Tuesday into early Wednesday as the ridge continues to weaken and the system sags southward. This will bring some light shower activity to the northwestern portion of the area- mainly to the Pacific Coast, the western slopes of the Olympics, and areas from King County northward. Overall rainfall amounts will be rather light, with areas across the Northern Interior likely only getting a few hundredths of an inch of rain. The highest amounts will be along the North Coast, where generally a quarter of an inch to half an inch of rain will be possible. Highs on Tuesday will be in the mid 50s to mid 60s.

An upper level ridge will then build back into the Pacific Northwest on Wednesday, with showers expected to taper throughout the day. Highs are expected to be in the lower to mid 60s across western Washington with mostly cloudy conditions in the morning becoming partly cloudy by the afternoon hours.

LONG TERM /THURSDAY THROUGH MONDAY/

Guidance remains in strong agreement with the upper level ridge building over the region on Thursday. A thermal trough will also build northward along the coast and will turn the low level flow offshore, helping to warm afternoon highs into the mid 60s to mid 70s across the area. Friday will be the warmest day of the week as the ridge axis pushes further inland and offshore flow persists through the morning hours. Highs will climb a degree or two and are again expected to be in the mid 60s to mid 70s- roughly 5 to 10 degrees above normal across the area. Overnight lows both Thursday and Friday will be in the mid 40s to low 50s.

A dissipating frontal system then looks to move into the area on Saturday as the ridge axis pushes further to the east. The best chances for rain remain along the Pacific Coast and across the North Cascades as the system moves over the area. A stronger, more organized frontal system then looks to move through the region Sunday into Monday, bringing more widespread chances of rain and breezy winds to western Washington. A dusting of snow for the higher peaks will also be possible on Monday as snow levels drop to 5000-5500 ft. Highs will cool over the weekend as conditions become more unsettled and only look to top out in the upper 50s to mid 60s. Overnight lows will generally be in the 40s and 50s.

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AVIATION

Widespread VFR today with clear skies. Cloud cover will start to increase this evening along the coast and spread into the interior overnight. Ceilings will gradually deteriorate along the coastline overnight into Tuesday morning, with MVFR ceilings expected by the afternoon. Otherwise, interior terminals expected to remain VFR Tuesday. Northerly surface winds will shift southerly Tuesday morning.

KSEA...VFR today with clear skies. Increasing cloud cover on Tuesday, but conditions expected to remain VFR. Increasing chances for MVFR ceilings towards the end of the the TAF period. Northwesterly winds around 5 knots this afternoon. Winds will become light and variable this evening before shifting southeasterly by 05Z.

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. Latest probabilities show there is a 65-90% chance for small craft wind gusts. 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. Additionally, guidance indicates possible headlines for the Strait on Saturday with gusts having a 50-60% chance of reaching small craft thresholds.

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SEW WATCHES/WARNINGS/ADVISORIES

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