133 FXUS66 KSEW 251052 AFDSEWArea Forecast Discussion National Weather Service Seattle WA 352 AM PDT Thu Sep 25 2025
.SYNOPSIS...Zonal flow will continue through Friday. A frontal system will graze the northern portion of the state, bringing the chance of showers. Widespread rain on Sunday and Monday as a frontal system pushes through the area. Unsettled and cooler conditions are favored to continue into next week.
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.SHORT TERM /TODAY THROUGH SATURDAY/...Pockets of patchy fog may form early this morning over portions of Western Washington. Latest satellite imagery already shows some patchy fog starting to develop along portions of the coast, southwest interior, and Puget Sound.
Zonal flow will continue over Western Washington today through Friday as an upper level trough moves inland over Canada. As the system pushes through Canada, shower activity may clip the northern portion of Western Washington: northern Olympic Peninsula, San Juan Islands, northern interior, and northern Cascades. QPF amounts are generally expected to be light, with the highest amounts likely over the north coast and northern Cascades. In addition, zonal flow over the region will generate onshore flow that will keep smoke to the east of the Cascades.
Temperatures today will be in the 50s along the coast/water and 60s along the interior. Cloud cover will increase throughout the afternoon and most will clear out by tonight. Southwesterly flow will bring slightly warmer temperatures on Saturday, with high temperatures in the low to mid 70s in the interior and low to mid 60s along the coast/water.
.LONG TERM /SUNDAY THROUGH WEDNESDAY/...Ensemble guidance is in good agreement that a troughing pattern will persist over Western Washington next week, keeping the chance of rain in the forecast. A frontal system is expected to move over Western Washington Sunday into Monday, bringing widespread precipitation to the region. A trough will follow behind the frontal system, bringing additional rainfall through midweek.
Temperatures on Sunday will be similar to Saturday. However, temperatures will cooldown on Monday. High temperatures will be in the low to mid 60s in the interior and mid to upper 50s along the coast/water Monday through midweek.
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.AVIATION...Southwest flow will increase aloft into Thursday as the upper ridge axis shifts eastward. Weak onshore flow tonight and clearing will likely brings many ares of IFR fog or stratus for the coastal areas, Strait of Juan de Fuca, and many Puget Sound terminals. Expect coverage to be more scattered with stratus forming in place rather than a strong push. Regardless, expect improvement in areas with low ceilings and/or visibility toward 18z. Additional mid and high clouds increase through the day ahead of a weak front. Expect west or northwest surface winds to develop for most by the afternoon.
KSEA...VFR conditions under clear skies and light winds early this morning. Expect IFR stratus to develop 12-14z in vicinity of terminal with around 35% chance of development at KSEA. Any stratus will scatter toward 18z Thursday. Surface winds light and variable this morning, but becoming increasingly from the northwest this afternoon at 6-7 kt. Increasing mid/high clouds this afternoon ahead of weak front, with stronger onshore push expected to bring stratus to terminal Thursday night/Friday morning. Cullen
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.MARINE...High pressure weakening over the waters today with a weak front clipping the northern portion of the waters late. Expect to see current advisory conditions across parts of the coastal waters to decrease through the morning, with the current advisory due to expire at 11 AM. Moderate confidence that conditions will subside ahead of schedule this morning. Attention that turns to stronger west/northwest winds tonight into Friday. Confidence isn`t quite high enough to issue another SCA for the Strait yet, but decent support from HREF and and NBM guidance to at least make this a possibility (40-60% chance) so will hold off for now and let the next shift refine the timing and extent. Seas will build to near or above 10 ft over the outer coastal waters Friday. A stronger front will reach the waters late Sunday, followed by a trailing disturbance into Monday. This could be the first stronger system of the season, with seas and winds both potentially reaching impactful levels. Cullen
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.SEW WATCHES/WARNINGS/ADVISORIES... WA...None. PZ...Small Craft Advisory until 11 AM PDT this morning for Coastal Waters From Cape Flattery To James Island 10 To 60 Nm- Coastal Waters From James Island To Point Grenville 10 To 60 Nm-Coastal Waters From Point Grenville To Cape Shoalwater 10 To 60 Nm-Coastal Waters From Point Grenville To Cape Shoalwater Out 10 Nm.
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NWS sew Office Area Forecast Discussion