Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA
Issued by NWS Seattle/Tacoma, WA
466 FXUS66 KSEW 241541 AFDSEW Area Forecast Discussion National Weather Service Seattle WA 841 AM PDT Sat May 24 2025 .SYNOPSIS...A building upper ridge will lead to warmer and dry conditions across Western Washington today. A weak front will produce a few showers and cooler temperatures on Memorial Day before upper ridging brings a return to drier conditions and warming temperatures into the middle portion of next week. && .SHORT TERM /TODAY THROUGH MONDAY/...The latest forecast remains on track with no updates this morning. A dirty upper ridge axis will shift onshore over the region this morning and the low level flow will briefly turn weakly offshore. This will allow interior area high temperatures to warm 5 to 10 degrees over yesterday under filtered sunshine. The upper ridge axis will shift east of the Cascades later today as an upper trough axis digs southward offshore around 140W. This trough and the associated front will approach Western Washington during the day on Sunday. Precipitation will likely hold off along the coast until Sunday evening, but increasing onshore flow and cloud cover will put a lid on temperatures. A weak front and the associated trough axis will press onshore across the area on Monday morning. QPF looks pretty light...especially over the rain shadowed portions of Puget Sound. Nonetheless, clouds and shower activity will hold high temperatures in the 60s for most of the lowlands. Upper ridging starts to rebuild into Western Washington by Monday night...heralding a return to drier conditions and warming temperatures as we move into the middle portion of the coming week. .LONG TERM /TUESDAY THROUGH FRIDAY/...The synoptic pattern amplifies once again Tuesday into Wednesday as another trough deepening west of 140W results in a strengthening upper ridge downstream over the Pacific Northwest. By early Wednesday, 500 millibar heights are still on track to approach 580 decameters, 850 millibar temperatures rise to near 16 C, and thermally induced low pressure expands northward the coast. All of this points toward some of the warmest temperatures we`ve seen thus far this year with interior areas from Seattle southward getting into the lower (or even mid) 80s F. A majority of the ensembles bring another weakening front into the area on Thursday, but there`s considerable uncertainty with regard to its strength and the ensuing cooling trend that will follow. 27 && .AVIATION...Upper level ridge to the east through Sunday with southwesterly flow aloft over Western Washington. Light flow in the lower levels. High clouds through Sunday morning with the exception of some MVFR stratus developing along the coast 06z-09z tonight. KSEA...Variable high clouds. Northeast wind 4 to 8 knots gradually turning WNW today. Winds switching to light south around 12z Sunday. Felton/McMillian && .MARINE...High pressure over the waters through tonight with a frontal system moving inland north of Vancouver Island. The high will weaken Sunday. Weak front moving through the waters late Sunday night and Monday morning. High pressure will rebuild Monday night and Tuesday. A thermally induced surface trough will move up the coastline Tuesday night then shift inland Wednesday. Low end small craft advisory westerly winds possible in the Central and Eastern Strait of Juan de Fuca later Monday behind the front otherwise no headlines through the period. Felton && .SEW WATCHES/WARNINGS/ADVISORIES... WA...None. PZ...None. && $$