FXUS66 KSEW 272139 AFDSEW Area Forecast Discussion National Weather Service Seattle WA 239 PM PDT Fri Sep 27 2024 .SYNOPSIS...Drier conditions through Saturday as zonal flow aloft prevails. A subtle trough will enter on Sunday increasing precipitation chances. An upper-ridge looks to take hold to start the new week however, a series of weak troughs will influence the pattern but most precipitation should stay north of the area. && .SHORT TERM /TONIGHT THROUGH MONDAY/...Mostly zonal flow aloft over the PNW along with broad ridging over the Rockies and saggy troughing off the coast of California. Conditions are drier across the forecast area as surface high pressure builds within this post-frontal environment. For tonight, we'll remain dry with minimum temperatures falling into the 40s and 50s. Can't rule out patchy fog developing due to residual surface moisture particularly along the river valleys. More dry weather expected into Saturday as the flow aloft backs towards the southwest. Offshore, an upper-trough positioned over the NE Pacific will track closer to cause the perturbation in the flow aloft. Conditions are to remain dry before rain chances return on Sunday. The aforementioned trough will swing into the region with the best chance of showers north of I-90 during the day before drying out at night. Then, upper-ridging will return to start the week on Monday as subsidence brings clear skies and abundant sunshine. Highs are to remain in the 60s with overnight lows largely in the 40s. .LONG TERM /TUESDAY THROUGH FRIDAY/...Ridging will persist into Tuesday but an upper-low out of the Gulf of Alaska will help to flatten it by midweek. Here we'll see the return of more rain chances. There are questions on how the pattern will exactly evolve around this time but rain amounts don't appear to be impressive. Guidance has a cold front sweeping across the region on Friday but uncertainty still exists in the track of its parent low. Temps in the extended may cool slightly with most locations seeing highs in the upper 50s to mid 60s. McMillian && .AVIATION...Mostly VFR with skies becoming mostly clear through the afternoon. A weak marine push Saturday morning will result in increased cloud cover with a 30% chance of terminals near the Puget Sound seeing MVFR in low stratus. Patchy fog also likely to develop early Saturday. Drier conditions will allow for a quick return to VFR by the afternoon. Surface winds generally out of the N 5-15 kt, switching to S/SW by Saturday evening. KSEA...VFR with north flow generally 8 to 13 kt, with occasional gusts to 15 kt through the evening. Winds will lighten overnight with some incoming cloud cover and patchy fog possible. Ensembles maintain a roughly 30% chance of conditions deteriorating below VFR in the early morning hours. Improvement by the late morning with VFR conditions through the rest of the day Saturday. 15 && .MARINE...A surface ridge will quickly build into the coastal and offshore waters today in the wake of a deep surface low that swept onshore near Haida Gwaii overnight. Surface ridging will build into the interior of southern British Columbia by tonight turning the flow northerly across area waters. A forecast surge of northerly winds has resulted in the issuance of a SCA for the East Entrance of the Strait of Juan de Fuca and Admiralty Inlet overnight into Saturday morning. Small craft advisories will also remain in place across the coastal waters and the west entrance to the strait as hazardous double digit seas will continue before they subside below 10 feet by Saturday night. A system passing mainly to the north of the area Saturday night and Sunday will enhance onshore flow with likely small craft advisory westerlies in the strait. Otherwise, conditions will remain fairly tranquil across area waters into early next week as high pressure remains in control. 27/15 && .SEW WATCHES/WARNINGS/ADVISORIES... WA...None. PZ...Small Craft Advisory until 5 AM PDT Saturday for Coastal Waters From Cape Flattery To James Island Out 10 Nm-Coastal Waters From James Island To Point Grenville Out 10 Nm-Coastal Waters From Point Grenville To Cape Shoalwater Out 10 Nm- Grays Harbor Bar-West Entrance U.S. Waters Strait Of Juan De Fuca. Small Craft Advisory from 11 PM this evening to 8 AM PDT Saturday for Admiralty Inlet-East Entrance U.S. Waters Strait Of Juan De Fuca. Small Craft Advisory until 3 PM PDT Saturday for Coastal Waters From Cape Flattery To James Island 10 To 60 Nm-Coastal Waters From James Island To Point Grenville 10 To 60 Nm- Coastal Waters From Point Grenville To Cape Shoalwater 10 To 60 Nm. && $$