Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA
Issued by NWS Seattle/Tacoma, WA
426 FXUS66 KSEW 182056 AFDSEW Area Forecast Discussion National Weather Service Seattle WA 156 PM PDT Fri Sep 18 2026 .SYNOPSIS... Seasonable conditions with morning clouds will settle into the region into next as onshore flow continues, with little change day to day. && .SHORT TERM /TONIGHT THROUGH SUNDAY NIGHT/... An upper level ridge will continue to progress eastward today, with southwest flow aloft and onshore flow at the surface. This pattern will continue through the weekend as a series of weather systems pass to the north, with little change day to day across western Washington. Seasonable temperatures will settle into the region, with highs generally in the upper 60s to lower 70s and lows in the upper 40s to lower 50s. Onshore pushes will also bring marine stratus inland each morning to varying degrees, with sunshine returning to most inland areas each afternoon. && .LONG TERM /MONDAY THROUGH FRIDAY/... This fall-like pattern is favored to continue into early next week as models have backed off on incoming precipitation. There will likely be little change once again day to day through at least Tuesday. Models have continued to trend drier into the middle of next week, and conditions may remain steady through next Friday. However, forecast confidence towards the end of the period remains low. 15 && .AVIATION... Northerly flow aloft this afternoon will turn more westerly tonight as an upper-ridge shift towards the area. Marine stratus is scattering and clearing to VFR across the interior this afternoon. Low clouds are likely to remain along the coast with MVFR cigs for terminals such as KHQM. Tonight, marine stratus (IFR/MVFR and isolated LIFR) will track inland once more - arriving in the interior between 08-12z Saturday. A cloudy morning will give way to VFR conditions around 19-20z. KSEA...VFR at the terminal and remaining through the evening. Stratus will return again overnight into early Saturday morning around 10-12z. Surface winds south to southwesterly 4 to 8 knots throughout the period. 41 && .MARINE... Onshore flow will persist into next week as a series of systems pass well north of the area. The onshore flow will increase somewhat early next week as weak frontal systems begin to clip the coastal waters. NBM probabilities for SCA gusts are increasing to 30-60% throughout the central/eastern Strait of Juan de Fuca Sunday night into Monday morning and 60-80% on Monday evening. && .FIRE WEATHER... Onshore flow will bring cooler temperatures, cloud cover, and increased moisture to the area today through the weekend, helping to minimize fire weather concerns. Fire weather concerns will remain minimal through the next week with cooler temperatures and chances of precipitation increasing mid to late week. && .SEW WATCHES/WARNINGS/ADVISORIES... WA...None. PZ...None. && $$