Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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970 FXUS66 KSEW 142145 AFDSEW Area Forecast Discussion National Weather Service Seattle WA 245 PM PDT Sun Jul 14 2024 .SYNOPSIS...
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An upper level ridge will remain in control over Western Washington through the first half of the for continued dry conditions and above normal temperatures. Minor day to day variations in onshore flow will bring the marine layer locally inland each night and morning. A subtle shortwave entering the area on Wednesday may bring an increased risk of convection over the Cascades.
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&& .SHORT TERM /TONIGHT THROUGH WEDNESDAY/...
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Broad upper level ridging remains in place over western Washington. Clear skies will prevail over the region this afternoon, with some leftover stratus hugging the coastline. Temperatures this afternoon will continue to remain above average, with high temps in the interior reaching the mid to upper 80s, and areas along the coast hovering in the mid 60s. Onshore flow looks to increase later this evening, which may pull the marine stratus a little bit further inland than the previous couple of mornings. High temperatures on Monday will still remain above average, but be a touch cooler, in the lower 80s for the interior, and low to mid 60s for coastal locations, with clear skies prevailing once again. Temperatures on Tuesday will warm as a thermally induced trough expands along the coast, with interior temps ranging from the upper 80s to even low 90s. Areas along the coast will warm into the mid to upper 70s. Latest ensemble guidance has been keying in on a negative tilted trough riding up along the west coast Tuesday night into Wednesday, pushing a weak shortwave sliding over the region with southerly flow aloft. This may open the door for elevated instability which could lead to increased convection over the Cascades. At this time, model guidance is a bit shaky on specifics, but it is worth noting for recreation and fire weather concerns. See the fire weather section for more details. .LONG TERM /THURSDAY THROUGH SUNDAY/...Upper level ridging looks to amplify through Saturday, which would result in once again above average temperatures through the region and minor fluctuations in onshore flow. There is disagreement heading into Sunday, where ensembles are showing a weak trough moving onshore into the beginning of next week. This would mean potentially some precipitation for the area, but, considering how far out it is, the most likely scenario is the continuation of warm and dry conditions for now. Mazurkiewicz
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&& .AVIATION...
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Mainly VFR with areas of IFR/LIFR along the coast in marine stratus. Surface winds generally W-SW 8 to 15 kt, decreasing overnight. Another marine push early Monday morning will allow low stratus to spread inland causing MVFR to IFR ceilings, potentially making it as far east as KSEA/KBFI/KPAE. Conditions will improve for most inland terminals by 18z-19z, allowing for another mostly clear day. KSEA...VFR with S-SW winds 12 kt or less. The marine push early Monday morning may bring MVFR to IFR ceilings (roughly 40% chance) as early as 12z-14Z Monday and improving by 18z. 15
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&& .MARINE...
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High pressure situated offshore will continue into the early week, allowing for diurnally driven pushes through the Strait of Juan de Fuca and marine stratus along the coast. Another round of borderline westerly SCA winds will be driven through the Strait of Juan de Fuca tonight into the early morning Monday. Weak flow will allow waves to come down from 6 to 8 feet today to 5 to 6 feet by Monday afternoon. Northerly flow will develop by mid-week as a trough deepens offshore. A surface front will slide northward across the region late Tuesday into Wednesday with additional fronts crossing area waters through the remainder of the week. While winds are favored to stay below criteria for now, seas will rise ta foot or two with the more active weather pattern to 5 to 7 feet. 15
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&& .FIRE WEATHER...
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High pressure will persist over the Pacific Northwest for continued warm and dry conditions, with low level onshore flow providing excellent relative humidity recoveries each night. Flow will start to turn southerly Tuesday night into Wednesday, with an increased potential for convection in the Cascades, with RH values remaining in the mid to upper 30s during this time. It is worth noting that especially with a pattern like this, with our fuels already being so receptive, all it takes is a rogue lightning strike from a thunderstorm to light these fuels. Will continue to monitor this threat as latest model guidance is not latching on to any specifics. For now, will monitor for the potential of thunderstorms and elevated instability. Mazurkiewicz
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&& .SEW WATCHES/WARNINGS/ADVISORIES... WA...None. PZ...Small Craft Advisory from 5 PM this afternoon to 2 AM PDT Monday for Central U.S. Waters Strait Of Juan De Fuca-East Entrance U.S. Waters Strait Of Juan De Fuca. && $$