Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA
Issued by NWS Seattle/Tacoma, WA
983 FXUS66 KSEW 301752 AFDSEW Area Forecast Discussion National Weather Service Seattle WA 1052 AM PDT Wed Sep 30 2026 .UPDATE...short term aviation update for impactful ceilings at metro terminals. && .SYNOPSIS... A frontal system will move out of Western Washington into this evening. High pressure builds aloft over the Pacific Northwest Thursday and Friday, with just a slight chance of precipitation. The upper ridge further builds over the weekend for drier, warmer conditions. && .SHORT TERM /TODAY THROUGH FRIDAY/... Drier conditions across Western Washington this morning as a few lingering light showers continue to taper this morning. With the abundant low-level moisture from yesterday`s rainfall and decreasing winds, expect to see the spatial coverage of fog to increase this morning toward daybreak. Low clouds gradually decrease through the day with at least partial sunshine for the afternoon. Not much change in the overall picture through Thursday. With the flow remaining zonal, there`s the potential for enough of an impact from the next disturbance clipping the far north as it passes across southern B.C. This brings some rain chances to the northern portions of the interior (mostly Whatcom/Skagit counties), but even for the areas that see rain it should remain quite light. As this disturbance exits the region on Friday, a few light showers may linger in the North Cascades, but dry conditions hold for most of the area. && .LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/... Ensemble guidance remains in fairly strong agreement for the weekend into early next week. the pattern would likely favor a return of high pressure and some light offshore flow. This could yield a somewhat mild start to October, with temperatures into the lower to mid 70s Sunday. The return of more onshore flow would return early next week as the high pressure nudges slightly eastward, bringing temperatures back down closer to 70 for daytime highs with the greater marine influence. Overall, though, mild and dry conditions expected for the long term period. && .AVIATION... Lingering MVFR to IFR conditions with fog and or low stratus that developed just before daybreak this morning. The lower ceilings stubbornly affecting KPAE have actually pushed further south into KBFI and KSEA, bringing a brief period of MVFR conditions with ceilings 1300-1500 ft. The expectation remains that conditions will gradually improve through midday to VFR levels at these locations as the boundary layer warms up. All other locations will remain VFR through the evening. Expect a similar scenario Thursday AM with elevated odds of MVFR to IFR conditions for a few locations, especially KBLI, KOLM and KPAE. Calm to light northerly winds early this morning will increase to 6-8 kt through the afternoon then ease late evening. KSEA...An area of stratus well to the north of the terminal has shifted south bringing 1300 to 1500 ft ceilings to the terminal briefly this morning. MVFR conditions will linger through 19/20Z then lift and scatter quckly to VFR levels through the afternoon and evening. Uncalibrated probabilities from LAMP for fog/low- ceilings Thursday morning remain less than 5%. Light NE winds early this morning will back to the NW in the afternoon and increase to 6-8 kt. Winds will ease this evening, veer back to the NE at 5 kt or less. && .MARINE... Seas subsiding over the coastal waters this week. Meanwhile, building high pressure over the waters with a thermal low pressure building north along the coast by the weekend. This will induce northerly to weak offshore flow over the waters, but speeds aren`t expected to be particularly strong. This will maintain seas generally 3-6 ft over the coastal waters and conditions short of advisory thresholds. && .FIRE WEATHER... Mostly dry conditions through the week ahead with additional wetting rain not expected. A few light showers across the north may develop with a passing disturbance late Thursday into Friday. Otherwise, attention turns to a warmer period with temperatures well into the 70s this weekend under stronger high pressure. This may bring a brief switch to light offshore flow as a thermal trough builds north over the region. This looks to shift eastward for a return to onshore flow and closer to normal conditions early next week. && .SEW WATCHES/WARNINGS/ADVISORIES... WA...None. PZ...None. && $$