textproduct: Seattle/Tacoma

SYNOPSIS

Upper level trough moving through Western Washington today bringing much cooler weather to the area. Brief upper level ridge later tonight into Thursday. Upper level low moving out of Gulf of Alaska moving down the British Columbia coast Thursday night and Friday. Upper level low reaching Western Washington Saturday moving east Saturday night, increasing the chances for thunderstorms.

SHORT TERM /TODAY THROUGH FRIDAY/

Showers are moving into the coastal zones this morning, with cloudy skies throughout western Washington. As the showers move inland, they will encounter drier air from yesterdays's warmer temperatures, so it may take time for any rain to reach the ground. Today will be significantly cooler, with highs in the 60s. Some evening convergence zone activity over King/Snohomish county is expected with a very slight chance for a lightning strike in the Cascade zones this afternoon.

Thursday an in between day with an upper level trough to the east and the upper level low just starting to exit the Gulf of Alaska. Convergence zone remaining intact in the morning hours keeping showers in the forecast for Snohomish County and Northern King county. Weak upper level ridge out ahead of the upper level low moving over Western Washington in the afternoon while the low level flow goes light. Even with afternoon sunshine highs mostly in the 60s.

Upper level ridge moving east Thursday night. Low level onshore flow returning bringing the marine layer back into the interior. Lows in the mid 40s to mid 50s.

Upper level shortwave spinning out of the approaching upper level low moving into Western Washington Friday returning at least a chance of showers back to the forecast. Air mass slightly unstable Friday afternoon. A thunderstorm can't be ruled out but chances are low, 20 percent or less. Cloud cover and showers keeping highs near 60.

Felton/21

LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/

Shortwave dissipating over Western Washington Friday night. Upper level low following Saturday keeping showers in the forecast. Increasing instablilty with the upper level low right over the top of the area in the afternoon. Chance of thunderstorms over all of Western Washington Saturday afternoon in addition to widespread showers. Highs once again near 60.

Upper level low moving east Saturday night with drying northwesterly flow aloft behind the low. Clearing skies along with the remnants of the cooler air mass will make for a chilly Sunday morning. Lows in the colder locations dropping into the upper 30s. Elsewhere lows in the lower to mid 40s.

Weak upper level ridge moving through Sunday but plenty of low level moisture hanging around making for a mostly cloudy/partly sunny day. Highs warming up into the 60s.

Another upper level trough moving into Western Washington Monday for more cool and showery weather. The trough will linger into Tuesday keeping a chance of showers in the forecast.

We had an increase in interest in the 90 day outlook with the calendar turning to June. The current 90 day outlook has a 60-70 percent chance of above normal temperatures for the June through August timeframe in Western Washington. In Seattle we have had above normal temperatures in June through August for 13 years in a row. The last year June through August had below normal temperatures was 2012 ( 0.7 degrees below normal ). It was close in 2024 with temperatures only 0.3 degrees above normal. The warmest June through August in the above normal streak was 2015 where temperatures were 5.0 degrees above normal. The remainder of the years range from 1.1 degrees to 3.2 degrees above normal. Felton

AVIATION

Southerly flow aloft will become westerly this evening as an upper level trough traverses the area. Mostly cloudy but VFR conditions this morning as a cold front begins to work its way onshore. Isolated showers will progress across the area this morning into early this afternoon as the front moves through. Slight (15-20%) chance of thunderstorms over the Cascades this afternoon but should remain very isolated.

Post-front, expect a convergence zone to keep showers lingering in Snohomish County through tonight, with a few more scattered showers lingering along the coast overnight. MVFR becomes increasingly probable Thursday morning for most. W/SW winds 5-10 kt should slowly increase this afternoon to around 8-15 kt with a few gusts to 20-25 kt possible. Winds generally remain around 6-12 kt overnight. Winds switch to N at PAE this evening and tonight.

KSEA...VFR today (lowering ceilings), then MVFR likely after 09Z Thursday morning. Convergence zone activity at this time is expected to remain north of the terminal. Southwest winds 8-12 kt kt with a few gusts to 20 kt at times.

HPR/62

MARINE

High pressure is moving inland this morning, with a cold front on track to move through the waters this morning/early afternoon. Shower activity will progress over the waters with little to no visual impacts expected with the rain rates. The main concern remains diurnal pushes in the Strait of Juan de Fuca. Small craft conditions remain expected today, and continuing into Thursday. Gale probability remains very low with this system. Another system passes over the waters Friday through Saturday, with a 20% chance of thunder with the shower activity. Probability of impacts with this system remain low at this time. Seas remain under 10 ft at all times in the forecast, with ranges of 4-6 ft or 6-8 ft.

HPR

FIRE WEATHER

The transition to onshore flow overnight has brought higher relative humidities to the area. This will alleviate fire weather conditions across Western Washington. The elevated threat for thunderstorms on Saturday will warrant continued evaluation for lightning strike potential on drier fuels. Right now, the wetting rain potential seems low. ERCs will decrease a bit now through the weekend thanks to the cooler temperatures and generally increased moisture, but there is still an increased threat in the drier grasses. Expect more on that as the week continues and Saturday approaches.

21/Felton

SEW WATCHES/WARNINGS/ADVISORIES

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