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Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA
Issued by NWS Seattle/Tacoma, WA
546 FXUS66 KSEW 031551 AFDSEW Area Forecast Discussion National Weather Service Seattle WA 851 AM PDT Wed Jul 3 2024 .SYNOPSIS...Dry and warm conditions continue this week. High pressure builds and moves over the region late in the week, bringing very hot temperatures this weekend and into the start of next week. The hot and dry conditions will also yield elevated fire weather concerns into the weekend. Some slight cooling is possible later next week, but temperatures are likely to remain well above normal. && .UPDATE...Very similar to yesterday morning we`ve got areas of marine stratus that will burn off through the day with very pleasant conditions by the afternoon. The main focus is on the heat later this week into early next week. A Heat Advisory has been issued across the region with additional details. The short range forecast is on track and no updates are planned. -Wolcott- && .SHORT TERM /TODAY THROUGH FRIDAY/...Another round of low clouds along the coast and portions of the interior this early this morning. This will scatter toward early afternoon though, with another mild afternoon featuring abundant sunshine in store today. High pressure will continue to build over the eastern Pacific and slowly shift eastward through the next few days. This will lead to a steading warming and drying of conditions across the region through the remainder of this week. The initially warm conditions through the Independence Day holiday will transition to hot by the end of the week. Expect high temperatures approaching the 90 degree mark for much of the Puget Sound region Friday (with locally hotter conditions south). This will bring widespread Moderate (Orange) HeatRisk levels by Friday. .LONG TERM /SATURDAY THROUGH TUESDAY/...The continued warm up looks to peak in magnitude for most of the region over the weekend. There remains strong agreement in the ensemble guidance supporting the ridge axis shifting more directly overhead Saturday and Sunday. While strong offshore winds are not expected, expect that at least some neutral or slightly offshore wind will eliminate any inland push of marine air and the very warm air mass will drive temperatures well into the upper 80s or 90s for much of the region. The forecast continues to closely trend with the 50th percentile data in the NBM, which remains warmer than the deterministic NBM for many days/locations. Overnight low temperatures will hover in the lower 60s for most of the region. These conditions will result in widespread HeatRisk levels of at least moderate/orange with some areas (including the urban heat islands) getting to the Major (red) category. Again, the overnight low temperatures are within a degree or two of the thresholds that would change things from Moderate or Major in many locations so there may continue to be some fluctuations day to day. However, it`s worth noting that the temperatures for Sunday (and Sunday night) have continued to trend upward for the interior. The potential for several days with high temperatures into the 90s is increasing, and this level of heat can cause to heat-related impacts, especially when considering the accumulated effect of heat and the very mild nights. While some onshore flow will likely bring some relief to the coast Sunday, this is unlikely to push deeper into the interior until at least Monday. However, temperatures are still likely to remain well above normal through much of next week. && .AVIATION...Upper ridge centered offshore will continue to build into the region today with northwesterly flow aloft. The low level flow remains onshore. Much like yesterday morning, a stratocumulus deck is gradually filling in across much of the interior this morning. Ceilings will lower to 1500 to 2000 feet at times for the interior terminals this morning before scattering and clearing this afternoon. Stratus along the coast is expected to burn off 20Z-22Z, but will return by around 06Z tonight. KSEA...Ceilings 1500 to 2000 feet this morning before lifting and scattering after 18Z. VFR conditions prevailing this afternoon and evening. Surface winds light S/SW this morning will veer N/NW 5 to 10 knots by mid afternoon into this evening. 33/27 && .MARINE...Light onshore flow will continue today into Thursday as 1030+ millibar surface ridge remains firmly in place over the offshore waters. Thermally induced low pressure will expand northward along the coast Friday and Saturday resulting in weak offshore flow at times. The thermal trough will shift into the interior on Sunday for a switch to onshore flow early next week. Quieter conditions are expected across area waters until late in the weekend when increasing onshore could necessitate some headlines for the strait and portions of the coastal waters. 27 && .FIRE WEATHER...Benign fire weather conditions are expected through Thursday. However, a strong upper-level ridge will amplify over the region bringing not only continued dry weather but hot temperatures starting Friday and lasting through early next week. A thermally induced surface trough appears to remain to our south around southern Oregon. This should keep discourage strong offshore winds which is a plus. However, hot, dry, and unstable conditions will be enough to maintain elevated fire weather conditions especially with fuels expected to dry out rapidly during this heat stretch. McMillian && .SEW WATCHES/WARNINGS/ADVISORIES... WA...Heat Advisory from noon Friday to 10 PM PDT Monday for Admiralty Inlet Area-Bellevue and Vicinity-Bremerton and Vicinity- East Puget Sound Lowlands-Eastern Strait of Juan de Fuca- Everett and Vicinity-Hood Canal Area-Lower Chehalis Valley Area-Olympics-San Juan County-Seattle and Vicinity- Southwest Interior-Tacoma Area-West Slopes North Cascades and Passes-West Slopes North Central Cascades and Passes- West Slopes South Central Cascades and Passes-Western Skagit County-Western Whatcom County. Heat Advisory from noon Friday to 10 PM PDT Sunday for Central Coast-North Coast-Western Strait of Juan De Fuca. PZ...Small Craft Advisory until 11 AM PDT this morning 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. && $$