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/

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

The cutoff low remains along the coast and will north into B.C. tonight/Friday morning with south flow aloft. The convection threat this afternoon has shifted to the coast and Olympics region this afternoon, where there are continuing thunderstorms in these areas moving to the north-northwest at around 30-35 mph. Thunderstorm tops have peaked at 30,000-35,000 ft, but the main threats continue to remain lightning, with reduced ceilings/visibilities in the rain shafts, and a lesser threat of small hail and gusty winds. A few ensemble members have convection flaring up again in the south sound moving into the Seattle metro from 23-02Z this afternoon, which will keep the PROB30's for thunder through early this evening before activity winds down. LAMP guidance is favoring MVFR conditions continuing for most terminals through tonight into Friday (with limited VFR). A few terminals (particularly along the coast, Kitsap and around KPAE) have 20-30% chances of IFR/LIFR conditions around 12Z. Southwest winds will continue through the TAF period for most areas at 5-10 kt, with a few gusts to 20 kt this afternoon/evening in the interior, and in the Strait of Juan de Fuca.

KSEA...Ceilings likely to remain predominately MVFR through Friday morning. There is a brief 20% chance of IFR around 15Z as ceilings lower in the morning before convection. This morning's convection has wrapped up, though there remains a 20-30% chance of another round of convection from 23-02Z if convection forms in the south sound and moves northeast. Southwest winds through the TAF, with gusts diminishing to 5-10 kt tonight/Friday.

HPR

MARINE

A low/trough remains over the waters, and will move north into B.C. tonight. Thunderstorms will continue over the coastal waters and portions of the interior waters this afternoon and evening before subsiding. A 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 regular onshore pushes continuing. Saturday afternoon and evening looks like the next best chance of winds exceeding 20 kt in the strait. A few portions of the coastal waters may get slightly windy next week, but confidence is low at this time for any headline worthy winds.

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

FIRE WEATHER

Showers and thunderstorms are mainly along the Olympic Peninsula as conditions have trended drier for the Cascades so far this afternoon. As a result, a RFW remains for the Olympic Mountains until tonight but the Cascades RFW has been canceled due to the lack of thunderstorm coverage. 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...Red Flag Warning until 11 PM PDT this evening for East Portion of the Olympic Mountains-West Portion of the Olympic Mountains-West Slopes of the Central Cascades Generally above 1500 Feet-West Slopes of the North Cascades Generally above 1500 Feet.

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.