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Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA
Issued by NWS Seattle/Tacoma, WA
490 FXUS66 KSEW 120941 AFDSEW Area Forecast Discussion National Weather Service Seattle WA 241 AM PDT Mon Aug 12 2024 .SYNOPSIS...Upper level troughing over the region will promote onshore flow and cooler temperatures the next several days. Isolated thunderstorms will be possible across the North Cascades today and Tuesday. More widespread chances of precipitation may return to western Washington by the weekend. && .SHORT TERM /TODAY THROUGH WEDNESDAY/...Troughing over the Pac NW will keep western WA mostly cloudy and cool over the next several days. No signs of the aurora from NWS Seattle overnight due to the cloud cover, but others were lucky with a few breaks. The focus for today will be showers and possible thunderstorms over the North Cascades once again, especially near the crest. There are some nocturnal showers near the crest early this morning but we should see activity increasing this afternoon and evening. Elsewhere, the coast may see a little light rain this morning under the stratus layer. Temperatures will track a few degrees cooler than average with highs in the 60s to lower 70s. The trough makes little progression on Tuesday and we`ll continue to see onshore flow and cloudy/cool weather. There`s another threat of showers and thunderstorms near the crest in the North Cascades. The trough exits east on Wednesday and we`ll see higher heights and slightly warmer conditions over western WA. Interior temperatures will reach the mid to upper 70s - just a degree or two shy of normals. NW winds will keep the coast in the 60s. 33 .LONG TERM /THURSDAY THROUGH SUNDAY/...An upper level low will drop down from Canada and spin offshore as we move though the latter half of the week. Onshore flow will be lighter, for the most part, and we should see more sunbreaks during the afternoon and early evening hours. Temperatures stick in the 60s and 70s with lows in the 50s. Showers (and possible thunderstorms) are expected in the mountains both Thursday and Friday. Shower coverage expands to all of western WA over the weekend as the low pulls in additional moisture. 33 && .AVIATION...Upper-low overhead with variable winds aloft. MVFR and low-end VFR stratus is increasing in coverage early this morning. This trend will continue before gradually decreasing in coverage as the day progress. A return to more widespread VFR is likely after the 21z time frame but there`s an isolated chance of some locations not improving at all. However, widespread stratus is certain to redevelop Monday night into Tuesday morning. Surface winds winds will remain west-southwesterly 5 to 10 kt throughout the TAF period. KSEA...Low-end VFR to MVFR cigs have been observed so far this morning. A gradual improvement to mostly VFR is expected as the day progress (after 21z). Winds remain southwesterly 5 to 10 kt. More stratus is slated to return Monday night into Tuesday morning. McMillian && .MARINE...Broad high pressure over the East Pacific will continue onshore flow over the area waters. Diurnally driven pushes down the Strait of Juan de Fuca will occur each evening with no signs of SCA level winds for the next few days. Seas are to range between 3 to 6 feet throughout much of the upcoming week. Can`t rule out visibility restrictions at times with the possibility of mist squeezing out of marine stratus. McMillian && .SEW WATCHES/WARNINGS/ADVISORIES... WA...None. PZ...None. && $$