Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA
Issued by NWS Seattle/Tacoma, WA
704 FXUS66 KSEW 291610 AFDSEW Area Forecast Discussion National Weather Service Seattle WA 910 AM PDT Fri Aug 29 2025 .SYNOPSIS...Upper level ridging will bring dry conditions to western Washington today before shifting eastward by this evening. An upper level low off the coast will influence the area this weekend, bringing slightly cooler temperatures and only a slight chance for showers. Upper level ridging returns Monday, bringing a return to warming temperatures and dry conditions. && .UPDATE...Generally quiet conditions across the region this morning. There remains widespread cloud coverage and a few isolated light radar returns centered over Kitsap County. The current forecast is on track and no updates are planned this morning. -Wolcott- && .SHORT TERM /TODAY THROUGH SUNDAY/...Latest satellite imagery continues to show the upper level center or circulation still in place over W WA this early morning, however shifted northward from 24 hours ago. For the southern three-quarters of the CWA, this has resulted in a more typical west-to-east steering flow. From the Skagit/Whatcom county line and on northward, a more monsoonal east- to-west steering flow remains. While this impacts the mid to high level clouds over the area, it has little effect on the low clouds/marine stratus along the coast. Switching over to radar, there is a curious band of echoes located over northern Pierce and southern King counties as of 145 AM PDT...stubbornly in between any ASOS stations, so it is difficult to see if they are actually precipitating. Their very presence, yet low intensity, suggests that at least some isolated spots in the south Sound and around the immediate Seattle metro area could see a stray sprinkle before sunrise...but no significant rainfall is expected. As stated in the synopsis, the main weather feature today will be upper level ridging building over the region which will slowly burn off any cloud cover for the interior while coastal stratus appears to be a little more stubborn, in at least some part due to the upper level low off the coast, but that will be discussed more in-depth momentarily. High temps today will be on average 1-3 degrees warmer than yesterday with most inland locations in the upper 70s to lower 80s while water-adjacent spots will run in the mid 60s to around 70. The main feature for the weekend, the upper level low off the coast, continues to remain organized but subsequent model runs from 24 hours ago to current have been persistent in associating less and less moisture with the feature. So while some slight cooling, down into the mid 70s to around 80 for the interior, is still on tap for Saturday...the chances for showers have dipped with only slight chance wording /10-20 pct/ in the forecast...and the higher end of that is mainly over the higher terrain of the Olympics and Cascades, with possibly similar chances over the islands. Timing for this remains more of an overnight Saturday/early Sunday morning event, if it occurs. Generally dry conditions resume for most of the day Sunday, even though the proximity of the upper low will still keep daytime highs below 80. 18 .LONG TERM /MONDAY THROUGH THURSDAY/...Intensifying upper level ridging to the east of the area looks to cause the upper low to retrograde back out over the Pacific waters, resuming its influence over W WA for the remainder of the forecast period. Daytime highs are expected to increase each day, with 90s returning to inland locations as early as Wednesday for Cascade valleys...becoming more widespread in the interior lowlands Thursday. The coast and other water-adjancent locations will generally remain in the lower to mid 70s for most of the long term period...the only exception could be Thursday where some potential offshore flow could nudge temps into the mid to upper 70s. 18 && .AVIATION...IFR/MVFR stratus along the coastline with VFR conditions and mid level cloud ceilings elsewhere. Light onshore flow early this morning will allow stratus to gradually fill in inland, but is favored to stay west of the Puget Sound and I-5 corridor over the Southwest Interior. Stratus will dissipate and burn off by 18z, but areas like KHQM and KCLM will struggle to break out today. Mid level clouds will thin out by the late morning as the upper level disturbance overhead dissipates with VFR continuing persisting for interior terminals. KSEA...VFR conditions with some passing mid level clouds early this morning. Winds trying to become northwesterly late this afternoon with the wind direction ending up in the 250-280 degree range generally staying between 4 and 8 knots. 15/Mazurkiewicz && .MARINE...Light south to southwesterly surface winds will continue over the coastal waters today. Periodic onshore flow will bring westerly pushes across the Strait of Juan De Fuca each evening, with the strongest push Saturday evening that may reach Small Craft Advisory criteria. Combined seas around 2 to 4 feet look to continue through the weekend and into the first half of next week before building to 4 to 6 feet. 15 && .SEW WATCHES/WARNINGS/ADVISORIES... WA...None. PZ...None. && $$