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Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA
Issued by NWS Seattle/Tacoma, WA
858 FXUS66 KSEW 171613 AFDSEW Area Forecast Discussion National Weather Service Seattle WA 913 AM PDT Mon Jun 17 2024 .SYNOPSIS...Light shower activity will linger today as an upper level trough shifts eastward. High pressure aloft will gradually build through the week, allowing conditions to dry out and warm up. A pattern change is on track for the end of the week as a trough brings wetter and cooler conditions to western Washington. && .SHORT TERM /TODAY THROUGH WEDNESDAY/...No planned updates to the forecast this morning and current trends are on track. 33 previous discussion...Light shower and virga activity will continue to push southward throughout the day today as moisture wraps around an exiting trough to the east. Combined with onshore flow, cloudy skies will stick around today and limit temperatures to the low to mid 60s for most areas. Instability will be lacking, so thunderstorms are unlikely to form this afternoon. Shower activity will taper off over the Cascades through the evening and early morning hours as drier air moves inland. High pressure will build into the region on Tuesday and Wednesday, allowing conditions to warm up and dry out. Clearing skies and a transition to more zonal flow aloft will allow temperatures to return to near-normal on Tuesday. Thermal troughing to the south and weak onshore flow will allow most inland lowland areas to reach the mid to upper 70s on Wednesday, while coastal areas peak a bit cooler near the 70 degree mark. .LONG TERM /THURSDAY THROUGH SUNDAY/...Warming will continue through the end of the week as low amplitude ridging continues to build across the region on Thursday and Friday. Most lowland areas apart from the coast will reach 80 degrees on Thursday, and temperatures are on track to peak on Friday. Temperatures Friday are slated to reach the mid 80s, roughly 10 to 15 degrees above normal. This may be the warmest day of the year so far for inland areas. However, the current forecast is still several degrees below daily records, and ensembles maintain a low (10% or less) chance of reaching record temperatures. The latest HeatRisk shows a moderate risk of localized urban heat stress that may impact vulnerable populations for the Seattle, Tacoma, and Olympia metro areas and will continue to be monitored. Ensembles are in good agreement over a pattern change by the weekend, with cooler and wetter weather on tap. Temperatures are favored to return to near-normal by Sunday, with a return of cloudy skies and a chance (20% to 30%) of light precipitation for most areas. Lindeman && .AVIATION...Northerly flow aloft today as a departing upper level trough continues eastward over the Rockies. A few lingering showers remain across western Washington, mostly confined to over the Cascade mountains. A few scattered showers remain possible across the region throughout the day today, diminishing this evening. Recent hi-res guidance is indicating the possibility for a convergence zone over northern King County this afternoon. Ceilings across the region are mostly MVFR, locally lower/higher in other locations. Ceilings look to slowly rise up to low-end VFR late morning into early afternoon with widespread clearing not expected today. Convergence zone development may keep ceilings locally lower. Ceilings look to lower back into widespread MVFR this evening through tomorrow morning. Southerly winds will continue across the area today, increasing up to 8 to 12 kt today. Winds will decrease this evening, becoming light southerly to variable. KSEA...Light showers east of the terminal this morning with IFR becoming MVFR ceilings. Ceilings should continue to rise to low-end VFR early this afternoon. A convergence zone north of the terminal may keep ceilings locally lower into the afternoon. VFR conditions should continue through this evening before lowering back to MVFR early tomorrow morning. Southerly winds continue through this TAF period, increasing to 5 to 10 kt this afternoon before decreasing this evening. LH && .MARINE...High pressure over the NE Pacific will maintain onshore flow over western WA this week. Highest winds and waves will be through the Strait of Juan de Fuca, mainly during the afternoon and evening hours. A Small Craft Advisory remains in effect beginning this afternoon through early Tuesday morning. Winds remain light through much of the forecast with high pressure remaining just offshore. The next frontal system is not expected until this weekend. Seas 4 to 6 ft are expected to persist through the remainder of this week. 18/LH && .SEW WATCHES/WARNINGS/ADVISORIES... WA...None. PZ...Small Craft Advisory from 2 PM this afternoon to 2 AM PDT Tuesday for Central U.S. Waters Strait Of Juan De Fuca-East Entrance U.S. Waters Strait Of Juan De Fuca. && $$