textproduct: Seattle/Tacoma

SYNOPSIS

High pressure will move in Tuesday and Wednesday for drier and warmer conditions. A pair of systems look to move through Thursday through the weekend for more chances for showers and cooler weather.

SHORT TERM /TODAY THROUGH THURSDAY/

Localized river valley fog this morning with stratus north of Everett, otherwise, mostly clear skies across the area. Dry and warmer weather will prevail through Wednesday with weak high pressure over the region. Max temperatures will peak on Wednesday with highs in the mid 70s to lower 80s. The coast will be cooler and in the 60s.

Broad low pressure over western Canada will sag south and send a trough through western WA on Thursday. The result will be increasing clouds, cooler conditions, a chance of showers (mainly central and northern Cascades). 33

LONG TERM /THURSDAY NIGHT THROUGH MONDAY/

Low pressure remains over the Pac NW Friday through the weekend as a closed low drops down from Canada. This will keep western WA cool and showery through the period. Expect highs in the 60s with overnight lows around 50. Look for dry and mild conditions early next week with temperatures close to average. 33

AVIATION

VFR conditions prevail across western Washington and will continue to do so with mostly clear skies. Some fog remains in place this morning the valleys but is not affecting any of the terminals and will burn off before 18Z this morning. Another round of valley fog and patchy marine stratus is expected to bring widespread MVFR to IFR once again early Wednesday morning, but is currently favored to remain west of KSEA/KBFI. Offshore flow overnight should limit its extent. Winds remain northerly 10 kt or less through the period.

KSEA...VFR conditions prevail through the TAF period. Northerly winds will generally remain light through Wednesday morning at around 4 to 8 kt.

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MARINE

High pressure will continue to build over the coastal waters through Wednesday. North to northwest winds will gradually increase into Wednesday as a frontal system slowly approaches, with potential for Small Craft westerlies through the Strait of Juan de Fuca Wednesday evening through Thursday morning. The frontal system weakens as it moves through the region on Thursday, allowing winds to ease across the region. Another weather system may move over the waters late Friday into Saturday, but no headline winds are anticipated at this time.

Seas around 4 to 5 feet will gradually build through Wednesday, reaching 7 to 10 feet by Thursday afternoon. This will also bring steep seas as short period waves from the stronger winds over the coastal waters begin to dominate. Seas will ease to around 5 to 6 feet by Friday and continue to stay near 5 feet through the weekend.

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FIRE WEATHER

High pressure through Wednesday will bring brief elevated fire weather concerns alongside a gradual warming and drying trend, with weak offshore flow Tuesday night limiting overnight relative humidity recoveries along the western Cascades. Additional drying throughout the day Wednesday will bring minimum relative humidity values over the Cascades to the 25 to 35 percent range, nearing critical thresholds in some areas near the Cascade crest.

By Thursday, fire weather concerns across western Washington subside as an upper level trough brings stronger onshore flow. Although this system will not bring much in the way of precipitation, relative humidities will rebound with much higher overnight recoveries.

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SEW WATCHES/WARNINGS/ADVISORIES

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