Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA
Issued by NWS Seattle/Tacoma, WA
565 FXUS66 KSEW 200925 AFDSEW Area Forecast Discussion National Weather Service Seattle WA 225 AM PDT Fri Sep 20 2024 .SYNOPSIS...Mainly dry weather today and Saturday. Rain spreads inland on Sunday for a chance of rain over the coast, north part and mountains. High pressure brings warmer weather moving into Tuesday. Rain returns by midweek with wet and cooler weather toward next weekend. && .SHORT TERM /TODAY THROUGH SUNDAY/...We`re under NW flow today with a ridge over the NE Pacific and a trough over western Canada. We may see isolated showers in the interior and Cascades today but otherwise looking mainly dry. Temperatures will continue to track cooler than average and in the 60s. The next frontal system stalls over southern B.C. on Saturday, leaving western WA dry and mild. The air mass over western WA is a little warmer with temperatures closer to average. Rain spreads into western WA on Sunday but mainly impacting the coast, north part near the border, and north/central Cascades. Precipitation from Seattle south is light (trace to a few hundredths if anything). 33 .LONG TERM /MONDAY THROUGH THURSDAY/...Light showers linger on Monday with warmer and drier weather on Tuesday with high pressure. Temperatures on Tuesday reach the 70s with a few low 80s possible. Wetter weather returns toward midweek as the ridge shifts east and moist S/SW flow sets up over western WA. We`re back to a troughing pattern moving toward the end of the week for additional showers and cooler weather. 33 && .AVIATION...Northwest flow aloft continues today as a weak upper ridge rebuilds into the region. Low level onshore flow will become light northerly later today. The air mass remains somewhat moist in the low levels with low MVFR in widespread stratus expected through late morning before lifting and scattering out to VFR 19Z- 21Z. Patchy fog/stratus will reform late tonight. KSEA...MVFR ceilings expected through 18Z then lifting and scattering this afternoon and evening. Current probabilities for low stratus reforming on Saturday morning are relatively low at less than 20%. Surface winds light southerly this morning veering west/northwest this afternoon then northerly 7 knots or less by evening. 27 && .MARINE...Onshore flow will gradually relax today as a weak surface low in the vicinity of Tofino dissipates and a surface ridge offshore expands in the coastal waters. The ridge will remain in place into Saturday, but weaken on Sunday as a frontal system moves onshore over southern British Columbia. No headlines are anticipated with this. Thermally induced low pressure expanding northward along the Oregon coast Monday into Tuesday will turn the flow more northerly or weakly offshore. Onshore flow resumes by the middle of the coming week as a weakening frontal system approaches the area. 27 && .SEW WATCHES/WARNINGS/ADVISORIES... WA...None. PZ...Small Craft Advisory until 3 AM PDT early this morning for Central U.S. Waters Strait Of Juan De Fuca-East Entrance U.S. Waters Strait Of Juan De Fuca. Small Craft Advisory until 5 PM PDT this afternoon for Coastal Waters From Cape Flattery To James Island 10 To 60 Nm- Coastal Waters From James Island To Point Grenville 10 To 60 Nm-Coastal Waters From Point Grenville To Cape Shoalwater 10 To 60 Nm. && $$