FXUS66 KSEW 102107 AFDSEW Area Forecast Discussion National Weather Service Seattle WA 207 PM PDT Fri May 10 2024 .SYNOPSIS...Upper level ridging across the Pacific Northwest will lead to continued warm and dry conditions through the weekend, though surface high pressure will peak in intensity today. A weak system will move across southern British Columbia Sunday into Monday. High pressure looks to build back across the region on Monday and Tuesday with unsettled weather likely making a return into the middle to end of next week. && .SHORT TERM /TONIGHT THROUGH MONDAY/...Clear skies with not a cloud in sight this afternoon thanks to broad high pressure anchored across the Pacific Northwest. No significant changes to the forecast high temperatures today and tomorrow, though increased downslope-favored areas given morning trends and NBM probabilistic guidance. Wouldn't be surprised to see a few locations top out in the upper 80s, with a 90% chance for high temperatures of at least 90F across eastern Grays Harbor and southwestern Mason County. Low temperatures tonight look to drop into the low to mid 50s across the interior lowlands. While unseasonably warm, this keeps HeatRisk values mostly in the Yellow/Minor to Orange/Moderate level, which means affects are more confined to individuals sensitive to heat, including those without effective cooling and/or adequate hydration. There may be some impacts in some health systems and in heat-sensitive industries. Clear skies across most of the area, aside from some scattered clouds along the coast, which will provide for good viewing conditions for the potential Aurora Borealis tonight. Refer to spaceweather.gov for more space weather information. High pressure begins shifting to our south and east Saturday, weakening cross-Cascade gradients and weakening the thermal trough along the coast. This leads to slightly cooler temperatures across the region, particularly along the coast and western Olympic Peninsula, though highs will still reach into the low 80s further inland. A few more high clouds Saturday as well, though mostly sunny conditions across western Washington. The ridge further flattens and shifts to our south Sunday into Monday as a weak shortwave and surface disturbance move across British Columbia, bringing in slight to chance PoPs for the northern and central Cascades. Snow levels remain well above pass-level from 6000 to 8000 feet. Highs in the low to mid 70s Sunday and low to mid 60s on Monday as a cold front shifts southward across the region in association with this system. .LONG TERM /TUESDAY THROUGH FRIDAY/...Confidence in the extended period from Wednesday onward remains low with the GFS and Canadian maintaining stronger upper-level ridging both in the deterministic and most of GEFS and GEPS runs. On the other hand, the EC and EPS ensemble members, along with some of the GEPS members currently favor a cooler and wetter pattern, which can be seen in the long range ensemble cluster analysis. A handful of GEFS and GEPS members keep the Seattle area dry through the entire week. For now, stuck with the NBM deterministic run for temperatures and PoP/Wx with highs near normal Wednesday, rising slightly above normal into the low to mid 70s by the end of the week. Davis && .AVIATION...Light winds aloft turning west as an upper-level ridge begins to deamplify over western Washington. VFR conditions with mostly clear skies through the TAF period. A few thin high cirrus clouds will pass through the northern parts of the region. There is the potential for a marine push along the coast, with low ceilings and low visibility possible for HQM. Surface winds light northerly to northeasterly 4 to 8 kt. Winds decrease to light and variable tonight, becoming northwesterly 4 to 8 kt tomorrow. KSEA...VFR with mostly clear skies, a few high clouds. NNE winds 4 to 8 kt before diminishing to light and variable (though predominately northerly) this evening. Northwesterly winds 4 to 8 kt tomorrow. LH && .MARINE...Broad high pressure over the northeast Pacific Ocean. Closer to home, a weakening thermal trough remains in place along the coast. The thermal trough will weaken throughout the day today, with north/northeasterly flow turning northwesterly tomorrow. Winds will begin to increase down the Strait of Juan de Fuca Saturday night, but will remain below any thresholds (up to 15 kt). High pressure well offshore will begin to build in closer to the region Sunday and into the beginning, and westerly winds will increase through the Strait of Juan de Fuca. A Gale Watch is in effect beginning Sunday afternoon with winds increasing to 20 to 30 kt, with gusts up to 35 kt possible (about 50% probability). High pressure will remain over the Pacific through the forecast, but model solutions differ with whether a frontal system will move through the region mid-week, leaving the forecast Wednesday and beyond highly uncertain. Seas 6 to 8 ft through this weekend and through the beginning of next week. Waves could approach 10 ft at times early next week as frontal systems approach the region from the north as the strength of these fronts is currently uncertain. LH && .HYDROLOGY...The daily hydrology discussion has ended until the start of the next rainy season; it will only be updated as needed. && .SEW WATCHES/WARNINGS/ADVISORIES... WA...None. PZ...Gale Watch from Saturday afternoon through Monday morning for Central U.S. Waters Strait Of Juan De Fuca-East Entrance U.S. Waters Strait Of Juan De Fuca. && $$