textproduct: Seattle/Tacoma

SYNOPSIS

Conditions are favored to trend drier over the weekend with near-seasonal temperatures. High pressure then builds over the area next week, bringing continued dry weather and well-above average temperatures along with Moderate HeatRisk.

SHORT TERM /TONIGHT THROUGH SATURDAY NIGHT/

An upper low (offshore) will continue to shift north tonight with showers and thunderstorms ending. Most of the activity is in the northern interior with isolated cells in the northern Cascades. The thunderstorm threat has ended in the Olympics and the Red Flag Warning was ended early. 33

Previous discussion...Showers and thunderstorms are persisting but mainly along the western half of the CWA (Olympic Peninsula and Island County). This activity will persist before decreasing in coverage into the evening. For tonight, drier weather is expected as the upper- low responsible for thunderstorms lifts north into BC. Minimum temperatures will fall into the lower to mid 50s.

Baggy troughing in the 500 mb levels Friday and Saturday as the aforementioned upper-low continues to track well into BC and Alberta. Can't rule out lingering showers (15-30% PoPs), primarily over the Olympics and North Cascades on Friday but conditions are favored to trend drier, especially into Saturday. High temperatures will be right around seasonal averages with highs in the lower 70s to near 80 F and overnight lows in the 50s. Daytime highs along the coast will be about 10 degrees cooler - in the 60s.

LONG TERM /SUNDAY THROUGH THURSDAY/

Guidance has the upper- level pattern into early next week featuring the return of high pressure across the region. A sharp warm-up in temperature is expected as highs top out 7-10 degrees above average for Monday and Tuesday. Widespread Moderate HeatRisk is favored during this time. There's disagreement in guidance regarding the evolution of the pattern midweek onward. GFS and Canadian ensembles are hinting at upper-level ridging persisting across the PNW with upper- troughing offshore. The ECMWF resembles are similar in ridging over the PNW but also over the offshore waters of the NE PAC, dissimilar than its GFS and Canadian counterparts. Nonetheless, well-above average temperatures are favored in the long-term forecast with no major signal for precipitation.

AVIATION

Generally low end VFR to MVFR this evening as showers and thunderstorm activity taper off across the region. Low end VFR to MVFR ceilings are favored to continue overnight into Friday morning, with localized areas of IFR/LIFR along the Pacific Coast and over the Kitsap Peninsula. Southwest winds will continue through the TAF period for most areas around 5-10 kt.

KSEA...Ceilings are favored to bounce between low end VFR and MVFR through early Friday morning as showers wrap up over the terminal. Chances for IFR ceilings increase between 12z-18z Friday morning, but confidence is low. Southwest winds around 5-10 kt will continue through the forecast period.

HPR/15

MARINE

Thunderstorms will continue to taper off over the coastal waters and portions of the interior waters this evening as a low pressure system moves over the area. A westerly push of winds through the Strait of Juan de Fuca will follow tonight into Friday, where a Small Craft Advisory is in effect. High pressure will rebuild off the coast this weekend, with daily onshore pushes continuing. Saturday afternoon and evening looks like the next best chance of winds exceeding 20 kt in the Strait.

Seas to drop to 4-6 ft tonight, with them building to 6-8 ft next week and potentially 9 ft in a few areas with periods at 8-9 seconds.

HPR/15

FIRE WEATHER

The Red Flag Warning for the Olympics has ended as the thunderstorm threat remains north and east of the area.

Fire weather concerns will linger through the remainder of the forecast period as a hotter and drier pattern returns quickly over Western Washington, especially into early next week. This has the potential for increasing fire activity from any new lightning starts from today's convection.

SEW WATCHES/WARNINGS/ADVISORIES

WA...None. PZ...Small Craft Advisory until 11 PM PDT this evening for Central U.S. Waters Strait Of Juan De Fuca-East Entrance U.S. Waters Strait Of Juan De Fuca.