Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA
Issued by NWS Seattle/Tacoma, WA
627 FXUS66 KSEW 170935 AFDSEW Area Forecast Discussion National Weather Service Seattle WA 235 AM PDT Tue Sep 17 2024 .SYNOPSIS...A upper level trough and associated front will push through the region late Tuesday for some rain showers into Wednesday. Drier conditions into Thursday before unsettled weather likely returns to the area through the weekend. && .SHORT TERM /TODAY THROUGH THURSDAY/...The forecast leans toward cooler conditions through Wednesday with troughing over the Pac NW. High temperatures will track in the 60s or a few degrees cooler than average. Expect lows in the 40s and 50s. Rain moves into the coast this afternoon with a few light showers reaching the interior as well. Look for drier conditions this evening as this system pushes south. May see light rain or drizzle in the central sound Wednesday morning where there`s convergence. Weak ridging nudges inland on Thursday for drier and slightly warmer weather. 33 .LONG TERM /FRIDAY THROUGH MONDAY/...Onshore flow prevails into the weekend as the flow aloft turns zonal. This opens the door as wetter Pacific systems roll in, with most of the ensemble members showing measurable rain. Skies remain mostly cloudy throughout with the onshore conditions and moist low level air mass. With this, temperatures will continue to trend cooler than average. There`s little overall change in the pattern moving into early next week for more fall-like weather. 33 && .AVIATION...West to southwest flow aloft will become east/northeasterly tonight as an upper level trough moving into the offshore waters shifts southward. A marine layer spreading inland will lead to widespread IFR or lower MVFR ceilings across the lowlands of Western Washington this morning. Moisture will deepen with the arrival of the trough and MVFR ceilings are expected to linger through the day. Areas of light rain are expected to develop midday mainly west of Puget Sound. KSEA...Marine layer will arrive before daybreak with IFR ceilings. These will lift to MVFR later this morning then persist through the day. Surface winds southerly rising to 7 to 10 knots by late morning. 27 && .MARINE...A weak surface low will shift southward over the offshore waters today into tonight, but is not expected to produce any headlines. Broad surface ridging centered well offshore rebounds Thursday into Friday. Northwesterlies may approach small craft advisory levels late this week across the outer coastal waters, otherwise fairly tranquil conditions are expected into early Saturday. Forecast confidence is low by early next week, but model ensembles suggest about a 20 to 30 percent probability of small advisory level winds for portions of the coastal waters with a frontal system on Sunday. 27 && .SEW WATCHES/WARNINGS/ADVISORIES... WA...None. PZ...None. && $$