Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA
Issued by NWS Seattle/Tacoma, WA
343 FXUS66 KSEW 232133 AFDSEW Area Forecast Discussion National Weather Service Seattle WA 233 PM PDT Mon Sep 23 2024 .SYNOPSIS...High pressure will result in mostly dry conditions through Tuesday along with warming temperatures. The next weather system will bring widespread rain, breezy, and cooler conditions to the region Wednesday, along with a chance of isolated thunderstorms. Another weaker system will arrive Thursday into Friday before dry conditions return this weekend. && .SHORT TERM /TONIGHT THROUGH THURSDAY/...After a rather dreary morning, widespread stratus is thinning this afternoon and patches of blue sky are expected by late in the day. An axis of high pressure is moving across the region today and will shift to our east by Tuesday. Another round of stratus is likely in the lowlands overnight but should burn off fairly quickly Tuesday. This will allow temperatures to warm several degrees, likely reaching the mid-70s to around 80 in the western Washington lowlands. In areas that don`t see stratus in the morning (mainly the Cascade valleys) could reach well into the 80s. On Wednesday, a fall-like frontal system will push through the region bringing widespread beneficial rainfall, cooler temperatures, as well as breezy to locally windy conditions. At this time, widespread peak winds in the 25-35 mph range look most likely, with locally higher gusts possible near the northern interior waters. With plenty of deciduous foliage still out there, wind impacts in the form of minor tree damage cannot be ruled out. Precipitation will taper off Wednesday night into Thursday morning. The break will be short lived as another, weaker system clips the area late Thursday into Friday bringing another round of precipitation to the region. Precipitation will taper off across the region through the day Friday. .LONG TERM /SATURDAY THROUGH MONDAY/...Forecast confidence in details over the weekend falls off quickly as ensemble mean favors largely zonal flow with dry conditions. However, embedded disturbances can`t be ruled out that could throw a wrench in the the forecast. With little moisture to work with, impacts from any disturbances should be minimal. -Wolcott- && .AVIATION...With the exception of coastal terminals, all are MVFR to VFR this afternoon. Surface winds will continue out of the southwest, with a gradual veering motion to the NNW after 02Z to 03Z. Trends indicate that MVFR to VFR cigs will continue through much of the overnight hours, with stratus and some fog reemerging after 10Z. Throughout Puget Sound, the probability of cigs below 020 ranges from 50 to 70 percent from midnight on through Tuesday morning. As of now, the breakout to more scattered clouds and MVFR to VFR cigs on Tuesday will likely be earlier than today, closer to 18Z to 19Z as opposed to late afternoon. This could change with updated guidance this evening. KSEA...MVFR at the terminal this afternoon as ceilings have lifted more appreciably from this morning`s IFR cigs. Surface winds are turning more southwesterly, and are still expected to veer to the NNW this afternoon, generally after 02Z. Once the winds are northerly, speeds are expected to stay below 6 kt. Another round of marine stratus is likely on Tuesday morning, with ensemble guidance giving 30 to 40 percent probabilities that ceilings will be below 030 after 10Z. An earlier breakout on Tuesday is possible and is progged for 18Z-19Z, but is subject to change pending updated guidance. Northerly flow remains through current data. Kristell && .MARINE...High pressure continues to influence the region through Tuesday for relatively calm seas and a period of offshore flow. Conditions are expected to change rather quickly as another frontal system arrives on Wednesday, bringing with it breezy conditions, rain and elevated seas. Winds through the Strait of Juan de Fuca on Wednesday afternoon could reach low end gale force. 8 to 10 ft seas are likely through Thursday morning over the coastal waters with heightened winds that may also approach small craft criteria at a minimum. A stronger frontal system is anticipated Thursday into Friday, where probabilistic wave height guidance is still keying in on above 50 percent likelihoods of seas of 12 to 13 feet over the coastal waters. This system will also be breezy, but information on anticipated speeds will come into more focus over the next few forecast iterations. Kristell && .SEW WATCHES/WARNINGS/ADVISORIES... WA...None. PZ...None. && $$