916 FXUS66 KSEW 062227 AFDSEW Area Forecast Discussion National Weather Service Seattle WA 327 PM PDT Mon Sep 6 2021 .SYNOPSIS...Upper level ridging will build into the region today and will continue to influence western Washington into Tuesday for dry conditions. An upper level shortwave will then move through the area on Wednesday, bringing the return of showers and the potential for a few thunderstorms. Western Washington will then stay under the influence of upper level toughing across the NE Pacific for a more unsettled pattern late in the week. && .SHORT TERM /TONIGHT THROUGH THURSDAY/...Upper level ridging centered across the Great Basin will continue to build northward into the Pacific Northwest today. Satellite this afternoon indicates morning stratus has scattered out across the region, with the majority of the area under sunny skies. Conditions will remain dry through the remainder of the day under the influence of the upper ridge and large scale subsidence. Afternoon highs will be in the low to mid 70s across the interior lowlands and in the 60s along the coast. The upper level ridge will continue to influence western Washington into Tuesday, with the axis expected to shift to the east. Overall, expect another dry and slightly warmer day, with afternoon temperatures increasing to the mid 70s to low 80s for the interior lowlands and 70s along the coast. A change to a more unsettled pattern starts early on Wednesday as the aforementioned ridge moves further to the east and an upper level shortwave moves across the region from the southwest. Some model guidance and upper level dynamics still favor the potential for elevated convection, however this will become dependent on instability. The tail-end of most hi-res guidance currently does not suggest much. Nonetheless, this feature will bear watching over the next 24 hours as it treks north toward the area and develops a negative tilt. Should instability lack, the system will simply bring the the return of more widespread showers to the region. Temperatures on Wednesday will be in the mid 70s to low 80s across the interior and 60s along the coast. Unsettled conditions will persist into Thursday as western Washington remains situated between upper level ridging across the Intermountain West and weak upper level troughing across the northeastern Pacific. This upper level pattern then acts to open the door to any weak systems approaching the region from the Pacific. Current guidance suggests a weak system will approach the region Thursday for continued precipitation chances. This will also aid in temperatures falling a few degrees, with afternoon highs expected to be in the low to mid 70s for the interior and 60s along the coast. 14 LONG TERM /FRIDAY THROUGH MONDAY/...Ensemble clusters in general agreement regarding weak upper level troughing across the northeastern Pacific generally influencing the region through the start of the long term. Additional weak systems look to approach western Washington early in the weekend for continued precipitation chances, at least for the Coast and Olympic Peninsula. The biggest question regarding these systems will be how much moisture they bring with them. The clusters then switch gear in the second half of the long term, as general consensus indicates the redevelopment of weak ridging across the northeastern Pacific late in the weekend and into early next week. Should this trend hold, it would act to dry conditions again late in the long term. 14 && .AVIATION...Clouds and stratus from this morning have largely scattered out, for all terminals at VFR, with only some fair weather cumulus leftover. Westerly flow aloft continues. Surface flow will turn around to a more northerly component this afternoon. IFR conditions in stratus are likely to redevelop Tuesday morning along and near the coast. KSEA...VFR ceilings in the 3000 feet and above range continuing this afternoon. Surface winds light S/SW becoming northerly 4 to 8 knots this afternoon and evening. SKC skies between 00-03Z. Kristell && .MARINE...Generally light winds expected across area waters today with broad surface ridge over the coastal waters extending into the Western Washington interior. Seas are generally calm this afternoon, between 2-4 feet. Thermally induced low pressure expanding northward over the interior of Western Oregon will tighten the gradient somewhat on Tuesday with northwesterlies reaching small craft advisory levels over portions of the coastal waters. Small craft advisory for the coastal waters will be in effect from 21Z Tuesday through 06Z Wednesday. A weak front will brush the waters by later Wednesday as an associated surface low lifts northeastward toward the south end of Haida Gwaii. This will increase onshore flow somewhat with advisory level westerlies possible in the strait Wednesday afternoon and evening. Seas look to elevate somewhat into Thursday afternoon to between 6-8 feet. Broad surface ridging rebuilds over the area for the conclusion of the week for generally light winds across area waters. Kristell && .SEW WATCHES/WARNINGS/ADVISORIES... WA...None. PZ...Small Craft Advisory from 2 PM to 11 PM PDT Tuesday for Coastal Waters From Cape Flattery To James Island 10 To 60 Nm- Coastal Waters From Cape Flattery To James Island Out 10 Nm- Coastal Waters From James Island To Point Grenville 10 To 60 Nm-Coastal Waters From James Island To Point Grenville Out 10 Nm-Coastal Waters From Point Grenville To Cape Shoalwater 10 To 60 Nm-Coastal Waters From Point Grenville To Cape Shoalwater Out 10 Nm. && $$ www.weather.gov/seattle