Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA
Issued by NWS Seattle/Tacoma, WA
962 FXUS66 KSEW 010433 AFDSEW Area Forecast Discussion National Weather Service Seattle WA 933 PM PDT Sun Jun 30 2024 .SYNOPSIS...High pressure will build far offshore tonight into Monday maintaining onshore flow keeping temperatures near normal for the next few days. High pressure shifts over the region late in the week about a sharp warm up starting around the Independence Day holiday and continuing through the weekend. && .SHORT TERM /TODAY THROUGH WEDNESDAY/...Shower activity has dried up for the most part this evening. Skies have cleared a bit over the southern portion of Western Washington. Will update the forecast and get rid of the chance of showers tonight. Some light showers are possible early Monday over the Cascades as another weak disturbance slides by to the east. Otherwise, low stratus along the coast tonight will try to make it inland Monday morning. The building offshore ridge will remain in place Monday through Wednesday. With it remaining offshore, this should maintain some onshore low level flow that will hold temperatures generally near seasonal normals through Wednesday with some morning clouds giving way to afternoon sunshine. Felton .LONG TERM /THURSDAY THROUGH SUNDAY/...Previous discussion follows. Strong agreement in the global ensemble guidance for the ridge to begin to build eastward over the Pacific Northwest around the Independence Day holiday, ushering in a period of above normal temperatures. The big question centers around how strong the ridge gets and when it moves over the region. The most likely scenario, which remains reflected in the forecast, brings widespread Moderate HeatRisk to the lowlands Friday and Saturday with temperatures climbing through the 80s and some local spots around 90 degrees. It`s worth noting that for next weekend, the spread in potential temperatures grows significantly, reflecting some uncertainty between various camps of ensemble solutions. There are subsets of each ensemble system that suggest either a weaker ridge or less persistent ridge. As a result, the deterministic NBM temperature values, which remain close to the 50th percentile of the distribution, continue to be used for the forecast today. With the increased temperature and lower relative humidities, it is expected that the grasses and other finer fuels will have time to begin further drying ahead of the holiday weekend. This may lead to elevated fire weather concerns in addition to the potential heat impacts late this week. && .AVIATION...Upper level ridge offshore with northwesterly flow aloft. In the lower levels light onshore flow. VFR ceilings inland with LIFR ceilings and reduced visibility along the coast. With the light onshore flow ceilings lowering over the interior after 10z with MVFR ceilings over most of the interior by 13z. Ceilings improving for the interior back to VFR 17z-19z. For the coast slow improvement overnight into Monday morning with ceilings improving to MVFR by 19z. KSEA...VFR ceilings overnight into early Monday morning. Ceilings lowering to MVFR around 13z. Ceilings improving to VFR 17z-19z with VFR ceilings MOnday afternoon. Variable wind 5 knots or less becoming southwesterly around 12z. Winds trying to go northwesterly after 21z. Felton Felton && .MARINE...An upper level trough is exiting western Washington this afternoon. There remains a weak surface low over the waterways, but otherwise high pressure is expected to build over the Pacific throughout the week, with stronger pushes of onshore flow this afternoon and Monday. Flow will become northwesterly over the coastal waters as the high begins to shift towards land. Breezy west winds of 15 to 25 kt Central/East Strait of Juan de Fuca through tonight (small craft advisory remains in effect). For tonight and tomorrow: low marine cloud coverage and fog is possible along the coastline. Some of the fog may be dense. A stronger push is expected Monday evening. Sustained winds are expected to reach 20 to 30 kt in the Central and Eastern Strait. The gale watch will remain in effect. The northwest flow Tuesday into Thursday over the outer coastal waters may approach 15 to 25 kt. Seas may also increase to 8 to 10 feet at 9 seconds during this period (will be 4 to 6 feet outside of Tuesday - Thursday period). HPR/Felton && .SEW WATCHES/WARNINGS/ADVISORIES... WA...None. PZ...Small Craft Advisory until 3 AM PDT Monday for Central U.S. Waters Strait Of Juan De Fuca-East Entrance U.S. Waters Strait Of Juan De Fuca. Gale Watch from Monday afternoon through late Monday night for Central U.S. Waters Strait Of Juan De Fuca-East Entrance U.S. Waters Strait Of Juan De Fuca. && $$