Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA
Issued by NWS Seattle/Tacoma, WA
680 FXUS66 KSEW 250324 AFDSEW Area Forecast Discussion National Weather Service Seattle WA 824 PM PDT Tue Sep 24 2024 .SYNOPSIS...A weather system will move across the region on Wednesday, bringing more widespread rain, breezy winds, and a chance of isolated thunderstorms to the area. Another system will move into the region Thursday night into Friday, before conditions dry out over the weekend. && .SHORT TERM /TONIGHT THROUGH FRIDAY/...Expect a quiet night tonight with increasing clouds and lows in the 50s. The previous discussion can be found below along with updated aviation and marine sections: Wednesday brings more fall-like weather as the ridge exits east and a trough moves inland. Temps will be back in the 60s and cooler than normal. We may see a little light prefrontal precip during the morning, then rain increasing through the afternoon as the main frontal band moves in. The air mass is slightly unstable over and near the Cascades where isolated thunderstorms are possible. Showers will shift toward the King/Snohomish line during the evening with a strong onshore push and setup for a Puget Sound convergence zone. We`ll see a brief break on Thursday, then more rain and wind moving through the region heading into Thursday night and early Friday. Again, more widespread rainfall amounts for the whole region with wetting rains in the mountains. Winds will be breezy overnight Thursday along the North Coast and North Interior with S gusts to 30-40 MPH. 33 .LONG TERM /SATURDAY THROUGH TUESDAY/...The weekend forecast, for now, is looking cool but quiet with weak troughing over the region. Not much moisture or forcing over the region with generally dry conditions. Highs will reach the lower to mid 60s with lows in the 40s and 50s. Broad high pressure covers the Pac NW moving into early next week, keeping the weather mild. Rain returns Monday night or Tuesday as the ridge pushes east. 33 && .AVIATION...Southwest flow aloft will increase into early Wednesday as a frontal system moves across the area. VFR high clouds for most areas this evening, with increasing LIFR cigs along the coast and into the Strait of Juan de Fuca. Cigs will lower tonight into Wednesday as the frontal system approaches the area. Generally MVFR/IFR cigs later tonight into Wednesday with LIFR cigs and vsbys along the coast. Rain will increase later tonight along the coast, and move into Puget Sound late Wednesday morning into the afternoon. Vsbys with the rain will likely range 2-5SM. Cigs will slowly lift towards VFR/MVFR later Wednesday afternoon. A convergence zone is also expected to develop over Snohomish and King Counties into Wednesday evening. Light winds this evening will increase from the S/SW into Wednesday morning, with breezy winds at times into the afternoon. KSEA...VFR cigs with high clouds this evening. MVFR stratus expected to develop generally between 09 to 10z, and continue through Wednesday. There is also approximately a 50 percent chance of IFR cigs in the morning, particularly between 11z to 17z. A front will move across on Wednesday, with rain chances, peaking from 17 to 22z. A convergence will then develop north of the terminal into Wednesday evening. Light NW winds this evening will transition S/SW between 06 to 08z, and increase on Wednesday. JD && .MARINE...Surface high pressure will linger over the coastal waters this evening with northerly/onshore winds and seas over the coastal waters generally 7 to 9 ft. A relatively strong frontal system on track to bring backing winds to south-southwest late tonight into Wednesday followed by northwest winds behind the front. There is also approximately a 40 to 60 percent chance of a brief period of SCA wind gusts as the front moves across the Coastal Waters, mainly between 300 and 900 AM, with brief SCA wind gusts possible over the northern inland waters Wednesday morning. The resulting push of westerlies through Strait of Juan de Fuca is then expected to bring small craft winds, 20 to 30 kt, with around a 20 percent chance of gusts hitting 34 knots or greater. Seas are expected to come up a bit to 9 to 10 ft with this front as well. Another, what continues to look stronger, front is expected to follow on the heels of the first - moving into area waters late Thursday. This will bring another round of stronger winds with a higher likelihood of gusty southeasterlies ahead of the front followed by another strong push through the Strait of Juan de Fuca during the afternoon and evening hours. Seas are expected to build further with this system - into the 13 to 16 ft range over the outer coastal waters Friday. && .SEW WATCHES/WARNINGS/ADVISORIES... WA...None. PZ...Small Craft Advisory from noon Wednesday to midnight PDT Wednesday night for Central U.S. Waters Strait Of Juan De Fuca-East Entrance U.S. Waters Strait Of Juan De Fuca. && $$