415 FXUS66 KSEW 252249 AFDSEW Area Forecast Discussion National Weather Service Seattle WA 349 PM PDT Fri Jul 25 2025 .SYNOPSIS...Zonal flow will continue into Saturday, maintaining cooler and cloudy conditions across western Washington. Southwest flow aloft will begin to develop on Sunday, kicking off a warming and drying trend with chances for thunderstorms towards the middle of next week. && .SHORT TERM /TONIGHT THROUGH MONDAY/...With low pressure to the north and high pressure to the south, zonal flow aloft will continue to bring moist onshore flow to western Washington through Saturday. High temperatures will be limited by the cloud cover this afternoon, reaching the upper 60s to near 70 and the upper 50s to near 60 along the coast. The weak trough over British Columbia will shift further inland on Saturday, bringing a repeat of cooler and cloudy conditions to western Washington. However, slightly less cloud cover on Saturday afternoon may allow temperatures to peak a degree or two warmer than today. A warming trend will begin on Sunday as a high pressure ridge begins to build over the south central US and a low pressure system deepens over the Gulf of Alaska. While conditions will stay dry through Monday, flow aloft will turn southwesterly and allow temperatures to warm up several degrees. Highs will return to near seasonal averages on Sunday and Monday with plentiful afternoon sunshine. .LONG TERM /TUESDAY THROUGH FRIDAY/...A deep upper level low will churn offshore through the extended period, generating southerly flow aloft over western Washington and injecting periods of moisture northward. Ripples in the southerly flow may generate thunderstorms throughout the week, especially over the Cascades and Olympics, where ensembles show potential for MUCAPE values as high as 500-1000 J/kg. While the exact details remain highly uncertain at this time, the threat for storms continues to be closely monitored. 15 && .AVIATION...A shallow trough in north B.C. will slowly fig southward today. The flow aloft will increase and turn from zonal to slightly west-southwest as it digs down over WA into Saturday. Stratus remains in place this afternoon along the coasts, Southwest Interior up into Kitsap/Puget Sound terminals. Terminals under the stratus remain MVFR this afternoon. Satellite shows clearing taking place on the east side of the Cascades (particularly south of I-90), and also some clouds eroding along the east Strait of Juan de Fuca. Given the lingering stability and lack of solar input to mix up, the cloud deck will linger a bit longer through the afternoon. Scattering of the main deck is anticipated from 20-22Z (though the coast will likely remain MVFR due to the onshore pattern). Winds this afternoon are still southwesterly 4 to 8 kt (gusty at KBLI to 20 kt and also Strait of Juan de Fuca areas due to push. Diffluence from the marine push through the strait will turn winds lightly northerly from 02-04Z through 09Z in Puget Sound. Another marine push Saturday morning will likely bring stratus. There is a 40-60% chance of MVFR in interior terminals, and 60-90% from Olympics to the coast. Highest chance of IFR (20-40%) is most of the coast, Olympics, Hood Canal, Kitsap, and north Puget Sound terminals. Some mist and possible drizzle may mix in spots. Improvements to VFR expected 18-21Z. KSEA...MVFR Cigs expected to scatter this afternoon between 20-22Z, with either SCT or FEW likely remaining in the evening around or below 5,000 ft. Southwest winds this afternoon 4-8 kt will likely turn northwest after 02-04Z through 9Z (expected at or below 5 kt), before returning to the southwest. Another marine push likely to bring stratus/mist and possible drizzle in the morning (as early as 12Z lasting 18-21Z) - 40% chance of MVFR and 15% chance of IFR. HPR && .MARINE...An upper level trough will bring increasing onshore flow today over the region. The trough will remain in place through Saturday before moving inland. A larger low will dip down from Alaska offshore through next week. For this weekend, the onshore marine pushes may bring stratus and mist/fog over portions of the waters Saturday morning (especially the inner coastal waters). Diurnal pushes through the Strait of Juan de Fuca will continue through the weekend. A small craft advisory continues for the central/east Strait of Juan de Fuca this evening, and the push Saturday evening/Sunday may produce gusts and potentially sustained small craft winds. Coastal seas will remain Seas will remain 5 feet or less throughout the weekend through next week. HPR && .FIRE WEATHER...No fire weather concerns through Monday. Conditions will start to warm up and dry out early next week as an upper level ridge begins to build over the Pacific Northwest. Concerns begin to increase going into the middle of next week as a trough slowly drifts south out of the Gulf of Alaska, and the flow aloft over the region turns southerly. This will allow for more moist air from the Pacific to move into the region and this pattern is indicative for the potential for thunderstorm development. While significant positive precipitable water anomaly values point towards mostly wet thunderstorms, fuels will be dry enough that any lightning could prove problematic. More details will be available as we get into next week, but we will continue to closely monitor how the pattern evolves. 62 && .SEW WATCHES/WARNINGS/ADVISORIES... WA...None. PZ...Small Craft Advisory from 5 PM this afternoon to 2 AM PDT Saturday for Central U.S. Waters Strait Of Juan De Fuca- East Entrance U.S. Waters Strait Of Juan De Fuca. && $$