Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA
Issued by NWS Seattle/Tacoma, WA
854 FXUS66 KSEW 042126 AFDSEW Area Forecast Discussion National Weather Service Seattle WA 226 PM PDT Sat May 4 2024 .SYNOPSIS...Cool and unsettled weather will continue over western Washington into early next week. A pattern shift can be expected by midweek as upper level ridging builds over our region, bringing drier and a much warmer conditions to our area. && .SHORT TERM /TONIGHT THROUGH TUESDAY/...Latest water vapor imagery shows a broad area of low pressure sinking southward into the Oregon and California border, continuing to push showers through our area. The boundary continues to make little progress, so expect maybe some lighter rain for more interior locations through this evening..along with areas up to the north in Whatcom county remaining mostly dry. Most of the rain this evening will be focused along the coast, the Olympia Peninsula, and Olympia southward as thats where the boundary is focused. High temperatures this afternoon hovering in the 50s, while areas in Whatcom County will experience a touch warmer temps, in the low 60s. The broad area of low pressure associated with an upper level trough will continue to move eastward inland on Sunday, but will still remain close enough to continue showers for western Washington. With another trough right behind it, onshore flow will be strong Sunday providing more wetter conditions, especially for interior locations. Along with rain showers throughout the interior, some snow can be expected in the higher Cascades.. generally around 4000 to 5000 feet, but will be rather light. As the upper level trough crosses the region into Monday, cooler air aloft will help produce some instability along with steep lapse rates, which could help the development of some isolated thunderstorms over the interior into Monday afternoon. Strong onshore flow will continue as well, also prompting the development of a potential Puget Sound Convergence zone into Monday evening. Unsettled showery conditions look to continue through Tuesday and Wednesday as the upper level trough lingers over the region. .LONG TERM /WEDNESDAY THROUGH SATURDAY/...There is strong support from ensemble guidance that a pattern shift is upon western Washington, with an upper level ridge building over the region starting on Wednesday. Although there are some small variations in timing and placement of the upper level ridge, there is a general agreement that much warmer and drier conditions will take place throughout much of the long term, with NBM high temperatures in the lowlands around mid to upper 70s into Friday and Saturday. Mazurkiewicz && .AVIATION...An upper low will move into the Oregon California border this evening with southeasterly flow aloft transitioning westerly on Sunday. Generally VFR north of SEA this afternoon with MVFR/IFR across the coast and southern Puget Sound. Cigs will slowly lower for areas of central Puget Sound this evening into tonight, with most areas in MVFR/IFR cigs by Sunday morning. Light rain will continue at times into early tonight, with another round of lighter rain on Sunday. Some improvement to cigs by Sunday afternoon, but generally MVFR to low-end VFR expected. A northerly component to the winds this afternoon will transition more southerly this evening, with southerly winds increasing tonight. KSEA...VFR mid clouds this afternoon with periods of light rain. Cigs will slowly lower this evening to MVFR generally between 01- 03z. Cigs will remain low-end MVFR with potentially periods of IFR tonight into Sunday morning. Cigs generally remain MVFR Sunday afternoon with light rain at times. Northerly winds will transition more southwesterly this evening, mainly between 00-02z. Southerly winds will then increase into Sunday morning. JD && .MARINE...A frontal system will move through the southern portions of the waters into this evening. Another weather system will move across the waters Sunday night into Monday. A northerly component to the winds this afternoon will transition more southerly tonight into Sunday. A westerly push through the central and eastern Strait of Juan de Fuca tonight will result in brief SCA wind gusts. West winds then increase through the Strait of Juan de Fuca again Sunday afternoon into early Monday for another round of SCA winds. Winds may also reach SCA for adjacent areas, including Admiralty Inlet and northern inland waters, south of the San Juan Islands, during this period. In addition, winds will increase Sunday afternoon into Monday morning for Puget Sound with an increased likelihood of SCA wind gusts during this period. Additional westerly pushes through the Strait of Juan de Fuca are likely Monday and Tuesday evening. Winds will then transition more northerly Wednesday into late week as high pressure builds into the area. Seas of 5 to 8 feet will continue into Monday before building to 9 to 12 feet Monday night through Tuesday. JD && .HYDROLOGY...No river flooding is expected over the next 7 days. && .SEW WATCHES/WARNINGS/ADVISORIES... WA...None. PZ...Small Craft Advisory from 6 PM this evening to 8 AM PDT Sunday for Central U.S. Waters Strait Of Juan De Fuca. Small Craft Advisory from 6 PM this evening to 5 AM PDT Sunday for East Entrance U.S. Waters Strait Of Juan De Fuca. && $$