Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA
Issued by NWS Seattle/Tacoma, WA
894 FXUS66 KSEW 152139 AFDSEW Area Forecast Discussion National Weather Service Seattle WA 239 PM PDT Sat Jun 15 2024 .SYNOPSIS...Unsettled, cool conditions will persist over Western Washington into Sunday as an upper level trough remains over the region. The trough will shift east of the region on Monday and a trend toward warmer and drier conditions will commence Tuesday through the end of the week as higher pressure aloft gradually rebuilds into the region. && .SHORT TERM /TONIGHT THROUGH TUESDAY/...Scattered showers and isolated thunderstorms continue across Western Washington this afternoon as an upper level trough axis remains in place over the area. With the strong June sunshine, modest instability will continue the thunder threat through sundown. In addition, increasing onshore flow will provide some focus for a convergence zone around the Snohomish/King county line into late this evening. Some of the precip rates could be locally heavy with the convection and, for that reason, a flood watch remains in effect for the Bolt Creek burn scar through this evening. The upper trough axis gradually shifts southeastward during the day on Sunday. The keeps a chance of showers in the forecast, though the instability indices decrease with time. The trough axis shifts east of the Cascades Sunday night into Monday with north to northwest flow aloft developing. Drier conditions are expected on Monday with residual showers mostly focused over the higher terrain of the Cascades. Heights continue to rise on Tuesday, but only modestly so with weak troughing aloft and low level onshore flow still in place. Nonetheless, plentiful sunshine is slated to return on Tuesday with temperatures bouncing back to near seasonal norms. .LONG TERM /WEDNESDAY THROUGH SATURDAY/...Looking ahead to the second half of the coming week, ensembles generally support the return of flat to low amplitude upper ridging with 500 millibar heights back into the 570s dam. With onshore flow continuing, some of the guidance might be a little overzealous with some interior locations getting into the 80s. Nonetheless, a return to seasonal temperatures and generally dry conditions during the extended period looks like a reasonable forecast at this time. 27 && .AVIATION...Broad upper level trough over the Pac NW with a cool and slightly unstable air mass over western WA. Showers continue across the region this afternoon and evening with a threat of thunderstorms too, especially near the King/Snohomish county line where there`s low level convergence. Shower and thunderstorm activity starts to fade by 03-06z this evening. Onshore flow will keep the low level air mass moist overnight with low clouds and MVFR conditions by morning. Another round of showers on Sunday as the cool upper low tracks overhead. 33 KSEA...Showers and possibly thunderstorms in the vicinity through around 01z this afternoon/evening. Thereafter, the focus for stronger convection will likely be north of the terminal in the convergence zone. Gusty S/SW to 25 kt easing after 03z. Low clouds and MVFR conditions possible by 12-15z Sunday. 33 && .MARINE...Onshore flow prevails tonight with highest wind and waves through the Strait of Juan de Fuca - a Small Craft Advisory remains in effect. High pressure over the NE Pacific will maintain light to moderate onshore flow moving through next week. 33 && .SEW WATCHES/WARNINGS/ADVISORIES... WA...None. PZ...Small Craft Advisory until 11 PM PDT this evening for Central U.S. Waters Strait Of Juan De Fuca-East Entrance U.S. Waters Strait Of Juan De Fuca. && $$