textproduct: Seattle/Tacoma

SYNOPSIS

Onshore flow continues into Sunday. Upper troughing will remain over Western Washington on Sunday, resulting in continued cooler temperatures and localized rain chances. Upper ridging builds offshore Monday with ridging over the Pacific Northwest much of next week.

SHORT TERM /TONIGHT THROUGH MONDAY/

The bulk of the moisture associated with todays front has weakened and move into the Cascades this afternoon. A convergence zone will continue into tonight across Snohomish County and vicinity, resulting in light rain at times. Upper troughing continues to move across the Pacific Northwest on Sunday for cooler temperatures, and chance of POPs, mainly from Snohomish County northwards and in the Cascades. Otherwise, morning clouds will slowly clear for some areas into the afternoon for sunshine. Temperatures will only peak in the mid 60s to mid 70s Sunday.

Upper ridging begins to build offshore Monday, allowing for drier conditions to return to western Washington and the beginning of a slow warming trend. Of note, winds will have a more north to northeast component beginning Monday, which will likely allow for some wildfire smoke from BC and WA fires to filter into Western Washington. This continues to be monitored.

LONG TERM /MONDAY NIGHT THROUGH SATURDAY/

The upper ridge will further build over Western Washington Tuesday into midweek, resulting in temperatures warming into the 80s to low 90s for portions of the area. Moderate HeatRisk returns Tuesday and Wednesday, especially for interior areas away from the water. In addition, continued north to east flow will allow for the threat of wildfire smoke to filter into Western Washington during this period.

Ensembles have trended more towards consistent ridging over the Pacific Northwest much of next week. Although the ridge may flatten a bit Thursday, continued warm and dry conditions are expected through late week. JD

AVIATION

Southwesterly flow aloft will become westerly tonight as an upper trough offshore moves onshore into southern British Columbia. Mostly VFR conditions prevail this afternoon except in and around convergence zone activity that will linger into this evening. Ceilings are expected to fall back to high end MVFR areawide tonight into Sunday morning. VFR conditions will then return across the region by midday Sunday. Gusty post-frontal west to southwesterly surface winds will ease later this evening.

KSEA...VFR conditions are expected to lower to high end MVFR thresholds early Sunday morning before lifting again by midday Sunday. Surface winds S/SW 15 gusting 20-25 knots will ease to under 10 knots toward 03Z this evening. Winds will veer to the N/NW after 21Z Sunday.

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MARINE

Post-frontal onshore flow will lead to small craft advisory winds in the central/east strait and central/south Puget Sound into this evening. High pressure will rebuild over the coastal waters Sunday and remain in place into early next week as thermally induced low pressure expands northward across the interior for quieter conditions across area waters.

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FIRE WEATHER

A frontal system has brought wetting rains to portions of the Olympic Peninsula this morning. Rain continues to progress eastwards into the Cascades this afternoon, especially into the North Cascades. This, along with cooler temperatures, will help ease fire weather concerns. There is a slight chance of thunderstorms in the North Cascades this afternoon but if one does occur it will be accompanied by rain. Continued onshore flow on Sunday will result in good RH recoveries and keep fire weather concerns at a minimum.

A warming trend will begin on Monday, with elevated fire weather concerns returning Tuesday through the majority of next week due to the prescience of upper level ridging. Minimum relative humidity values begin to drop into the 20 percent range on Monday for Cascade Valleys and south Puget Sound, with lower RH values around 20 percent Tuesday and Wednesday in these areas. Although a slight uptick in onshore flow may return Thursday into late week, RH values will remain low, with continued dry conditions. JD

SEW WATCHES/WARNINGS/ADVISORIES

WA...None. PZ...Small Craft Advisory until 10 PM PDT this evening for Central U.S. Waters Strait Of Juan De Fuca-East Entrance U.S. Waters Strait Of Juan De Fuca-Puget Sound and Hood Canal.