Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA
Issued by NWS Seattle/Tacoma, WA
616 FXUS66 KSEW 181603 AFDSEW Area Forecast Discussion National Weather Service Seattle WA 903 AM PDT Fri Sep 18 2026 .SYNOPSIS... The return of onshore flow to the area will bring more seasonable temperatures and morning clouds to western Washington daily through the weekend and into early next week. Upper level troughing developing over the northeastern Pacific next week will open the door for some systems to make their way into the region, with rain chances increasing mid to late week. && .SHORT TERM /TODAY THROUGH SUNDAY/... The latest forecast remains on track this morning with no updates. An upper level ridge will shift eastward today and over the weekend as an upper level low over eastern OR continues to make its way eastward out of the region. Onshore flow will continue in the low levels through the weekend, bringing rather seasonable temperatures and daily morning cloud cover to western Washington. Stratus may linger along the coast at times over the weekend, particularly today and again on Saturday, but expect stratus to scatter each day across the interior for some afternoon sun. Afternoon highs will be in the low to mid 70s across the interior and in the mid 60s along the coast. Morning lows will be in the upper 40s to low 50s. && .LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/... Ensembles hint at the pattern changing next week as upper level troughing develops across the northeastern Pacific. While mostly dry conditions look to persist across western Washington through the first half of the week, the development of southwest flow aloft over the area will open the door for systems to make it into western Washington mid to late week. At this time, rain chances look to increase midweek as a weak system brushes the region, with more widespread rain chances following late week. High temperatures will generally trend in the upper 60s to low 70s across the interior and in the 60s along the coast. Morning lows will be in the upper 40s to mid 50s. 14 && .AVIATION... Northwest flow aloft will turn westerly tonight as an upper ridge axis just offshore shifts eastward across the area. The low level flow is light onshore. Marine stratus has made its way across the interior this morning but is forecast to burn back toward the coast by 19-20z. VFR conditions will prevail across the interior this afternoon with stratus making a return and likely with greater coverage on Saturday morning. KSEA...IFR/MVFR stratus currently at the terminal this morning and will likely persist through 18Z or so before lifting and scattering out to VFR for the afternoon. Stratus will return again overnight tonight and likely take longer to clear on Saturday. Surface winds south to southwesterly 4 to 8 knots. 27/41 && .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. 27 && .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. 14 && .SEW WATCHES/WARNINGS/ADVISORIES... WA...None. PZ...None. && $$