Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA
Issued by NWS Seattle/Tacoma, WA
998 FXUS66 KSEW 302316 AFDSEW Area Forecast Discussion National Weather Service Seattle WA 316 PM PST Sun Nov 30 2025 .SYNOPSIS... The overall pattern for the week looks to remain on the cool with a few periods of precipitation. Showery precipitation will brush the area Monday into Tuesday and not again until more widespread precipitation threatens the region Thursday into Friday. Temperatures late in the week should also trend a bit warmer. && .SHORT TERM /TONIGHT THROUGH TUESDAY NIGHT/... Cool, but sunny and dry conditions will close the weekend out this afternoon. Already seeing some high level clouds stream into western Washington from the northwest, this will continue overnight as an upper level system rides over the ridge into British Columbia. Another chilly and foggy start looks to be on tap for parts of western Washington late tonight into Monday morning, especially across the southern Sound and Chehalis Valley. One wildcard here may be the high clouds overnight - especially to over the northern half of the area - which may help limit some of the radiational cooling. HREF and REFS continue to show a series of weak upper level disturbances waves riding over the upsream ridge Monday into Tuesday. Some members show the first of these waves earlier Monday morning, with potentially a second sometime Monday night into early Tuesday. This will bring periods of showers Monday into Tuesday morning. For the most part this will be light rain to the lowlands - however overnight lows especially in the outlying areas away from the water will dip to near freezing, so that any early morning showers that do pan out especially Monday morning, could contain a rain/snow mix. For the mountains light snow with accumulations less than 2 inches is expected - mostly Stevens Pass northward. Temperatures Monday and Tuesday will trend a little cooler than normal - especially the overnight lows. && .LONG TERM /WEDNESDAY THROUGH SUNDAY/... The upper level ridge will continue to drive the downstream weather through Wednesday night. Ensembles are consistently maintaining the eastern Pacific ridge well into Thursday, with some variability showing up in the form of a system riding over the ridge into Brittish Columbia Thursday. LREF ensembles do hint at a scenario behind this with a second, more organized Pacific system moving into the Gulf of Alaska Friday. This would result in a regionally wetter pattern for much of British Columbia, Washinton and Oregon. 35% of the LREF members are showing a stronger variation of this pattern, which would focus most of the heavier precipitation on the northern British Columbia coast and lesser amounts through much of western Washington through Friday into at least the start of the weekend. This pattern will likely result in warmer conditions going into Friday with both low and high temperatures trending above normal Friday into the weekend. && .AVIATION... A weak upper level system will brush the area Monday. Northerly flow aloft will weaken and become westerly Monday. Ceilings will remain VFR through the remainder of the day. Increasing mid and high level clouds Monday morning will result in overall VFR ceilings ranging between 3,500 and 10,000 ft. There remains a good chance for another round of radiational fog or low ceilings, especially in the river valleys from King County Southward - similar to Sunday morning. Calm winds or very light winds 3-6 kt out of the east/northeast are expected across most terminals. KSEA... VFR conditions with a few high clouds this afternoon and evening. Shallow fog is expected to develop again overnight to the east of the terminal along the Green River, and is not expected to affect the terminal. Lower confidence in fog forming Monday morning with most guidance keeping the odds below 40%. Winds will remain light north/east 3-5 kt. && .MARINE... High pressure will continue to build over area waters throughout the next week, with a series of systems crossing the waters. While conditions remain benign today, a weak front will pass over the Pacific Northwest later on Monday, bringing in elevated northwest winds over the outer coastal waters likely reaching SCA criteria alongside elevated seas. Conditions will calm mid-week before an additional weather system towards the end of next week brings in elevated westerly winds with potential for Gale force westerlies through the Strait of Juan de Fuca on Friday and next Saturday. However, forecast models continue to show some uncertainty over wind strength towards the end of next week. Seas around 6 to 8 feet today will build to 9 to 12 feet on Tuesday afternoon, easing back down to 5 to 7 feet by late Wednesday. Seas are expected to build as high as 10 to 15 feet feet towards next weekend with the next incoming system. 15 && .HYDROLOGY... River flooding is not expected over the next 7 days. && .SEW WATCHES/WARNINGS/ADVISORIES... WA...None. PZ...None. && $$