Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA
Issued by NWS Seattle/Tacoma, WA
827 FXUS66 KSEW 300403 AFDSEW Area Forecast Discussion National Weather Service Seattle WA 903 PM PDT Fri Aug 29 2025 .UPDATE...Satellite imagery shows a combination of low and high clouds over the area this evening with the low clouds along the coast and near the Strait of Juan de Fuca and the high clouds over the interior. Temperatures at 9 pm/04z were in the 60s and lower 70s. Current forecast on track. Previous discussion with updated aviation section below. && .PREV DISCUSSION... /issued 215 PM PDT Fri Aug 29 2025/ .SYNOPSIS...Upper level ridging will shift eastward by this evening. An upper level low off the coast will influence the area this weekend keeping temperatures seasonable. The probability of precipitation this weekend has fallen to single digit percentages for most areas. Upper level ridging returns Monday, bringing a return to warming temperatures and dry conditions. Well above normal temperatures are expected by mid- week. .SHORT TERM /TONIGHT THROUGH SUNDAY NIGHT/...Stubborn clouds have kept temperatures down across much of the region, a welcome relief for many. By tonight into Saturday, an upper level low spinning off the coast will draw nearer, bringing some additional cloud coverage to the region, but providing insufficient moisture to produce much in the way of precipitation. This will keep temperatures near seasonable levels through the weekend, but will also make nailing specific temperature forecast challenging since they will be somewhat sun-dependent. Chances for any precipitation have dwindled to less than 10% across the board and the chances for thunderstorms are even lower. .LONG TERM /MONDAY THROUGH FRIDAY/...As we move into next week, the upper level low remains just offshore but a west coast ridge is expected to amplify significantly Tuesday and Wednesday. By Wednesday, this is expected to result in temperatures rising back up into the 80s to low 90s across the region, persisting through at least Thursday. This will result in another period of heat with widespread HeatRisk values in the Moderate (orange) category and isolated Major (Red) HeatRisk in favored areas. This will also bring another period of fire weather concerns given the dry conditions. See the FIRE WEATHER section for more details. There is an overall signal for decreasing temperatures by Friday. However, there is a decent signal for temperatures to remain above normal beyond the day 7 time frame. -Wolcott- .AVIATION...Southerly flow aloft as an upper level low remains well offshore. High level clouds over the interior made for a colorful sunset. MVFR ceilings along the coast and along the Strait of Juan de Fuca with isolated IFR ceilings near Bremerton. While the onshore gradients are not very strong dew point temperatures remain in the mid 50s to lower 60s. Stratus forming over the interior 09z-12z with IFR ceilings at the higher terminals and MVFR ceilings at the lower locations. MVFR stratus continuing along the coast and near the Strait. Stratus dissipating over the interior around 18z with MVFR ceilings most of the day along the coast. KSEA...High clouds overnight with IFR stratus arriving at the terminal 12z-14z. Stratus dissipating around 18z with more high clouds Saturday afternoon. Southwest wind 4 to 6 knots becoming north northwesterly around 00z. Felton .MARINE...Varying degrees of onshore flow will continue throughout the waters into this weekend. Westerly pushes down the Strait of Juan De Fuca can be expected each evening, with the strongest push likely happening Saturday evening. Winds may reach Small Craft Advisory criteria, but right now confidence is low. Surface high pressure looks to develop over the coastal waters by midweek next week. Combined seas around 2 to 4 feet will continue throughout the weekend and into the first half of next week. Seas will then build to 4 to 6 feet by midweek. Mazurkiewicz .FIRE WEATHER...Weak onshore flow into the weekend is expected to keep temperatures in check with good to excellent nightly relative humidity recoveries. An upper level low parked offshore over the weekend could trigger isolated thunderstorm activity over the North Cascades late Saturday, but probabilities remain quite low...capped at around 10 percent. This offshore low will shift away from the area early next week with strong upper ridging rebuilding across the area. As a result, temperatures are expected to climb once again to well above average. Afternoon relative humidities in the 25-35% range are expected, with some higher terrain locations could get as low as 15-25%. Wednesday and especially Thursday are the days of most concern for hot, dry, and unstable conditions across the majority of the area. Fuel moisture levels are already low across much of Western Washington and the upcoming very warm and dry weather will further cure both live and dead fuels. 27 && .SEW WATCHES/WARNINGS/ADVISORIES... WA...None. PZ...None. && $$