textproduct: Seattle/Tacoma

SYNOPSIS

Cloudy skies will continue to scatter today as high pressure promotes a warming and drying trend through Thursday. Near normal temperatures and partly cloudy conditions are expected to return through the weekend and into early next week with continued low level onshore flow.

SHORT TERM /TONIGHT THROUGH THURSDAY NIGHT/

Clouds have slowly scattered this evening leaving most areas partly cloudy. Cloud cover will continue to decrease this evening, but with winds decreasing, that will open the door for some localized patchy fog in sheltered areas and river valleys. Lows tonight remain on track for the mid 40s to low 50s. 62

A high pressure ridge will slowly build into the region tonight through Thursday, bringing a warming and drying trend to western Washington. Temperatures will warm up to near-normal Wednesday under mostly clear skies, with highs generally in the mid 70s. A thermal trough building along the coast will shift inland on Thursday, inducing cooling along the coast with even warmer temperatures further inland. Temperatures Thursday will be the warmest of the week, with highs in the mid to upper 70s and around 80 degrees for some areas along the Cascade foothills and valleys and over the southern Interior.

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LONG TERM /FRIDAY THROUGH TUESDAY/

High pressure offshore will continue to influence the weather pattern over the weekend and into early next week, maintaining seasonable temperatures and dry conditions. Onshore flow will continue to promote morning cloud cover with plenty of sun breaks in the afternoons. Forecast models continue to hint at a potential pattern change early next week, though deterministic models continue to push back the timing of an approaching trough as the Pacific ridge holds on.

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AVIATION

North to northeast flow aloft tonight as a low digs southward and weak ridging noses over the area. VFR conditions this evening with clearing skies. Winds will continue to ease, becoming light to calm through early Wednesday morning. Clearing skies, light surface winds, and subsidence aloft will allow for areas of valley fog to develop, with the greatest chances being at the usual fog prone locations. (OLM, PWT, PAE, HQM) Clear skies will takeover the IFR/LIFR conditions late Wednesday morning. Winds Wednesday will pick up out the north 5 to 10 kt.

KSEA...VFR through the evening/early tonight with north winds 5 to 10 kt decreasing to 5 kt overnight. There remains a 15-25% chance of IFR conditions in the morning. Model guidance has 10-15% LIFR probabilities of vicinity fog to the north and south of the terminal. Time period for formation is from 13-17Z, with clear skies Wednesday afternoon. Winds increase out of the north Wednesday 5-10 kt.

HPR/62

MARINE

A thermal trough will build low pressure along the coast Wednesday into Thursday. This will cause the winds to briefly turn offshore. Once the thermal trough moves inland on Friday, the onshore flow will return with weak systems passing to the north this weekend. The likelihood of winds reaching headline thresholds during the next seven days is low, but portions of the coastal waters and the Strait of Juan de Fuca may see gusts approaching 20-25 kt as the weak system looks to move through early next week. Seas will hold around 3-6 ft through the forecast period.

HPR/62

FIRE WEATHER

A brief warming and drying trend will kick off today and continue into Thursday as high pressure builds offshore. Surface winds will briefly turn offshore on Wednesday as a thermal trough builds along the Pacific coast. Weak offshore flow will continue through Thursday, causing additional drying with relative humidity values bottoming out in the mid 20s to low 30s in the North Cascades and lowlands south of the Puget Sound. The thermal trough will shift inland on Thursday ahead of the return of onshore flow, which will minimize fire weather concerns through the weekend and into early next week.

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SEW WATCHES/WARNINGS/ADVISORIES

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