Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA
Issued by NWS Seattle/Tacoma, WA
458 FXUS66 KSEW 110435 AFDSEW Area Forecast Discussion National Weather Service Seattle WA 835 PM PST Wed Dec 10 2025 .SYNOPSIS... A persistent atmospheric river will continue to bring periods of moderate to heavy rain and gusty winds to western Washington into Thursday. Widespread significant river flooding is underway and will continue through the next couple of days. Minor coastal flooding due to astronomical high tides will also pose concerns for the northern Salish Sea coastlines through much of the week. Wet and unsettled conditions will continue into early next week. && .SHORT TERM /TONIGHT THROUGH FRIDAY NIGHT/...As per current radar, rainfall continues over W WA with the focus remaining over the northern half of the CWA. Numerous flood warnings are in effect, both for rivers and for areas that have already seen significant rainfall. Forecast remains on track for atmospheric river to sink southward overnight for additional rains for much of the CWA for much of Thursday. For additional forecast details, please refer to the Previous Discussion section below. From Previous Discussion...A strong atmospheric river is currently ongoing across western Washington bringing a flurry of impacts including widespread moderate to heavy rainfall. Cascade foothills have been hit exceptionally hard with over 4.00" of rainfall observed for locations such as Skykomish and Grotto so far today. Moisture-laden soils have been become unstable, leading to reports of landslides. This amount of rainfall has also lead to a plethora of swollen rivers in flood stage. More hydrological detail is provided in the hydro section below. The following key messages with this atmospheric river are outlined below: * HEAVY RAIN: Current satellite imagery shows a long fetch of cloud coverage spanning near the vicinity of the Hawaiian islands to the PNW. This airmass of tropical origin is the atmospheric river that will continue to bring widespread moderate to heavy rainfall into early Thursday. A nose of forecast IVT values are exceeding 700 kg/ms, entering WA this evening but should subside overnight into Thursday morning. This coincides well with stout 850 mb winds upwards of 50-55 kt, serving as a conduit of precipitation generation along the Olympics and Cascades. An additional 4-8" of rainfall is in the forecast for the mountains through Thursday morning. Can`t rule out localized higher amounts. 3-6" is favored for the foothills and rain shadowing will keep the lowlands with lower totals, with 1-3" expected. Rain shadowed areas of Kitsap Peninsula and Admiralty Inlet won`t exceed an inch. The atmospheric river will gradually taper off into Thursday afternoon but can`t rule out lingering showers and residual river flooding. * WINDS: Breezy winds will continue across western Washington this evening, with gusts reaching 40 mph. Winds will gradually lessen overnight into Thursday morning but with water-logged soils, downed trees and localized power outage can`t be rule out during this time. As mentioned, the atmospheric river will taper off by Thursday afternoon. However, lingering showers will remain in the forecast through Saturday before upper-level ridging builds and displace disturbances well off to our north. Temperatures in the short-term forecast will remain well-above average with highs in the lower to mid 50s, between 5-10 degrees above average this time of the year. && .LONG TERM /SATURDAY THROUGH WEDNESDAY/... As mentioned, ensembles have signaled high pressure amplifying over the region into Saturday, potentially bringing some relief to continued wet conditions across western Washington. This will be short lived, with the next weather system on track to cross the Pacific Northwest on Sunday as a weak cold front enters. Additionally, a potentially very wet system on its heels into Monday. It is likely that flooding impacts will linger into the weekend, and conditions will continue to be closely monitored, even with precipitation dwindling in intensity. && .AVIATION... An atmospheric river system will continue to produce widespread visibility and ceiling impacts due to heavy rain this afternoon and evening, as well as gusty winds. Terminals are primarily reporting IFR this afternoon (with pockets of MVFR and LIFR). Low level moisture and additional rain (some of which may be heavy at times) will likely keep visibilities down in most terminals through tonight/Thursday, with rain diminishing during the day Thursday. Ceilings are expected to be slow to improve to MVFR through the afternoon, with a low probability of improvement out of IFR in the south terminals through the day Thursday. Winds this afternoon remain breezy out of the southwest at 15-25 kt gusting to 35 kt. Speed shear remains more of a concern (compared to direction shear) with southwest winds expected at higher speeds aloft. Winds will decrease early Thursday morning down to 5-10 kt. A push of northwesterlies through the Strait of Juan de Fuca will turn winds briefly north/northeast in the Puget Sound terminals between 06Z- 12Z, before returning to the south. Winds will become calm to light and variable by Thursday afternoon. KSEA...IFR conditions likely to continue through the TAF period with rain (some of which may be moderate to heavy at times), low ceilings and mist. Small chance for improvement to MVFR late Thursday afternoon before returning to IFR in the evening. Winds SW 10-15 kt gusting to 30 kt through roughly 12Z, then a brief window of NE winds 5-10 kt between 12-16Z before returning to the ESE. Winds drop to under 5 kt late Thursday afternoon, become light and variable. HPR && .MARINE... A frontal system associated with an atmospheric river will continue to push across the region through Thursday. Moderate to heavy rain and areas of mist will reduce visibilities at times. Winds remain breezy out of the southwest this afternoon, with a few gale force gusts still possible in the inner coastal waters through the evening. Headlines remain in place for small craft elsewhere. Post-front, the winds will turn west through the Strait of Juan de Fuca tonight into the Admiralty Inlet. Winds will decrease substantially going into late Thursday, with rain showers tapering back as high pressure moves in. Another system next weekend will likely produce another round of strong southwest winds. At this time, there is a medium chance for gale gusts in the coastal waters Sunday and Monday, and in the Strait of Juan de Fuca Monday and Tuesday. Seas Wednesday at 8 to 12 ft will decrease to 6 to 8 ft Friday through Sunday, increasing to 12 to 16 ft early next week with the next system. HPR && .HYDROLOGY... Most rivers across western Washington will be affected by this second wave of AR moisture and many flood warnings remain in effect. Consult weather.gov/seattle for the latest. While some uncertainty does still remain in regards to the exact flood levels and stages, many river forecast points are projected to reach major flood stage and may even approach or exceed the previous floods of record. It will be critical to monitor the forecasts now and through the next seven days. With the wet antecedent soil conditions, the landslide threat across the region will increase with this system. Potential has also increased for debris flows over area burn scars, which will continue to be monitored. Urban and small stream flooding, as well as areas with poor drainage, should be alert to the potential for localized nuisance flooding and ponding on roadways. Low water crossings may become impacted or impassable. && .SEW WATCHES/WARNINGS/ADVISORIES... WA...Flood Watch through Friday afternoon for Cascades of Pierce and Lewis Counties-Cascades of Snohomish and Northern King Counties-Cascades of Southern King County-Cascades of Whatcom and Skagit Counties-City of Seattle-Downtown Everett / Marysville Area-Eastern Kitsap County-Eastern Strait of Juan de Fuca-Eastside-Foothills and Valleys of Central King County-Foothills and Valleys of Pierce and Southern King Counties-Foothills and Valleys of Snohomish and Northern King Counties-Foothills and Valleys of Thurston and Lewis Counties-Foothills and Valleys of the North Cascades-Foothills of the Western and Southern Olympic Peninsula-Grays Harbor County Coast-Island County- Lake Crescent Area Including US 101-Lower Chehalis River Valley-Lowlands of Lewis and Southern Thurston Counties- Lowlands of Pierce and Southern King Counties-Lowlands of Western Skagit and Northwestern Snohomish Counties- Lowlands of Western Whatcom County-Middle Chehalis River Valley-Northern Hood Canal-Northern Washington Coast- Olympia and Southern Puget Sound-Olympics-Port Townsend Area-San Juan County-Shoreline / Lynnwood / South Everett Area-Southern Hood Canal-Western Strait of Juan de Fuca- Willapa and Black Hills. Wind Advisory until 10 PM PST this evening for City of Seattle- Downtown Everett / Marysville Area-Eastern Kitsap County- Eastside-Foothills of the Western and Southern Olympic Peninsula-Grays Harbor County Coast-Lower Chehalis River Valley-Lowlands of Lewis and Southern Thurston Counties- Lowlands of Pierce and Southern King Counties-Middle Chehalis River Valley-Northern Washington Coast-Olympia and Southern Puget Sound-Shoreline / Lynnwood / South Everett Area-Southern Hood Canal-Willapa and Black Hills. PZ...Small Craft Advisory until 4 AM PST Thursday for Admiralty Inlet-Central U.S. Waters Strait Of Juan De Fuca-East Entrance U.S. Waters Strait Of Juan De Fuca-Grays Harbor Bar-Northern Inland Waters Including The San Juan Islands- Puget Sound and Hood Canal-West Entrance U.S. Waters Strait Of Juan De Fuca. Gale Warning until 10 PM PST this evening for Coastal Waters From Cape Flattery To James Island Out 10 Nm-Coastal Waters From James Island To Point Grenville Out 10 Nm- Coastal Waters From Point Grenville To Cape Shoalwater Out 10 Nm. Small Craft Advisory from 10 PM this evening to 4 AM PST Friday for Coastal Waters From Cape Flattery To James Island Out 10 Nm-Coastal Waters From James Island To Point Grenville Out 10 Nm-Coastal Waters From Point Grenville To Cape Shoalwater Out 10 Nm. Small Craft Advisory until 4 AM PST Friday 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. && $$