Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA
Issued by NWS Seattle/Tacoma, WA
531 FXUS66 KSEW 080332 AFDSEW Area Forecast Discussion National Weather Service Seattle WA 832 PM PDT Sun Jul 7 2024 .UPDATE...Temperatures remain very warm this evening, with temps generally 2-6 degrees warmer than 24 hours ago. This will set up a warm night, particularly across interior areas away from the water. Lows will likely range in the upper 50s to mid 60s for most, with little relief to the heat overnight. Otherwise, hot conditions again on Monday. No major forecast updates to this forecast. && .SYNOPSIS...Hot and dry conditions will persist under a strong upper level ridge through the first half of the week. Some relief is expected around midweek as the ridge moves eastward and weakens. However, above normal temperatures and no precipitation will remain. && .SHORT TERM /TONIGHT THROUGH THURSDAY/...Yet another day of very hot temperatures is well underway across Western Washington. At this hour, many locations have climbed into the 80s along the coast and a mix of 80s and lower 90s through the region. We may again see a few record high temperatures for the date fall, with Hoquiam already toppled today. Not much in the way of significant changes in store with high pressure over the region and the thermal low pressure building up over the region into Monday before pushing eastward Tuesday. This will maintain very hot temperatures through the early part of next week, with areas of Moderate (orange) to Major (red) HeatRisk expected through the interior portions of western Washington. Overnight lows will also remain in the lower 60s for areas inland, making for slow relief from the very hot daytime highs. Still expect Monday and Tuesday to be the warmest days of the week for most with the upper ridge axis moving eastward over the region. This will bring some light onshore influence back to the immediate coast into the afternoon, but little help for the interior with the thermal low pressure building overhead and cutting off much in the way of surface wind. Additionally, expect very warm nights in the mountains as the subsidence inversion strengthens. Have extended the heat advisory for the coast through Tuesday morning. While temperatures along the immediate coast will begin to moderate and see more significant overnight relief, there remains some question of how far inland the marine influence will be able to push. As a result, extended this to cover through the Monday night period after one more fairly warm day away from the coastline. Tuesday will be notably cooler for the coastal areas and into the Olympics as onshore flow begins to return. Areas as far as Chehalis, Olympia, and Shelton may see some moderation by Wednesday morning. This will be quite slow to push further into the interior with Wednesday remaining quite warm through the Puget Sound region (especially after another very warm night). This may require some extension of the heat advisory for areas from Seattle and east into the Cascade valleys. One other note with the stronger onshore flow as it arrives late Wednesday: forecast guidance has trended notably stronger with some gusty winds as the trough pushes east. This will be most notable along the coastal areas, but will need to monitor the potential for gusty winds ahead of the more humid air, especially as it relates to fire weather concerns. .LONG TERM /FRIDAY THROUGH MONDAY/...Still some minor differences emerging in the timing of the ridge weakening as a weak shortwave moves across the region, but ensemble guidance remains in fairly strong agreement that it will be enough to shift the pattern back down from the extremely hot and dry pattern to one that is probably better described as fairly warm. Increasing onshore flow should bring a return of higher daytime humidities with good overnight recoveries, and high temperatures that are only climbing into the 80s. While this is some 10-ish degrees cooler than where we`ll be in the preceding days, this will be a continuation of above normal temperatures through the second half of the week with still no significant prospects for precipitation in sight for the local area. Cullen && .AVIATION...Northwesterly flow aloft continues as high pressure amplifies over the west. VFR conditions throughout the TAF period, except at KHQM where IFR/LIFR conditions are expected late tonight through sunrise tomorrow as a weak marine stratus push develops around 06-09Z. N/NE winds continue tonight at around 4 to 8 kt, increasing to 8 to 12 kt tomorrow. KSEA...VFR conditions throughout the TAF period. N/NE 4 to 8 knots tonight, increasing to 8 to 12 kt by tomorrow afternoon. LH && .MARINE...High pressure remains situated offshore, with a thermal trough along the west coast and north/northwesterly winds over the coastal waters. Generally benign marine conditions will persist through the first half of the week. A surface front looks to sweep over the coastal waters Wednesday night into Thursday for increased onshore flow and for stronger pushes down the Strait of Juan De Fuca. Winds look to become elevated over the coastal waters and through the Strait through the end of the week. Coastal seas 4 to 6 feet through the first half of the week, gradually increasing to 6 to 8 feet by the end of the week. Maz && .FIRE WEATHER...As expected, strong high pressure is continuing to bring very warm and dry conditions to the region. With the additional factor of instability, the red flag warning for the Cascades zones (658 and 659) will remain unchanged. Elsewhere, the primary concern for the lower elevations and foothills south and east of Puget Sound will be the continued critical afternoon relative humidity values. For these zones, there`s at least one factor (fuel readiness, instability or winds) that remains lacking, but given the continued trends there remains the potential for needing a Red Flag Warning for additional zones by Tuesday. Some onshore flow will bring somewhat higher humidities for the coastal and Olympics zones Monday, but it could be at late as Wednesday before portions of the Cascades see notable improvement. && .SEW WATCHES/WARNINGS/ADVISORIES... WA...Heat Advisory until 10 PM PDT Tuesday 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 until 11 AM PDT Tuesday for Central Coast-North Coast-Western Strait of Juan De Fuca. Red Flag Warning until 11 PM PDT Tuesday for West Slopes of the Central Cascades Generally above 1500 Feet-West Slopes of the North Cascades Generally above 1500 Feet. PZ...None. && $$