FXUS66 KSEW 160248 AFDSEW Area Forecast Discussion National Weather Service Seattle WA 749 PM PDT Mon Apr 15 2024 .SYNOPSIS...Upper level troughing continues to bring cooler temperatures and showers back to western Washington through Tuesday. Ridging will then return midweek for warmer and drier conditions, followed by a weak frontal passage over the weekend. && .SHORT TERM /TONIGHT THROUGH THURSDAY/...Current satellite imagery shows W WA continues to be reside under cloud cover as a weak upper level trough sinks south into the area. Current radar remains fairly sparse with some scattered showers making their way onto the coast and, perhaps most noticeably, a PSCZ over eastern portions of Jefferson county and extending into central Snohomish. This feature remains fairly stationary at the time of this writing /730 PM PDT/, but echoes remain light with generally amounts of up to around a tenth of an inch possible. With minimal impacts expected from this system, inherited forecast looks to remain on track and see no reason for any evening updates at this time. For additional forecast details, please refer to the Previous Discussion section below. 18 From Previous Discussion...Zonal flow aloft this afternoon as an upper level trough slides southeastward through British Columbia, maintaining cooler and showery conditions for our area. Recent radar imagery this afternoon shows a developing convergence zone around southern Snohomish/northern King county this afternoon. This feature will likely stick around through much of the evening for central Puget Sound and start to dissipate late tonight. Scattered showers do look to stay around for majority of the area, but latest guidance really shows very spotty coverage with them. High temperatures today look to remain noticeably cooler from previous days, topping out in the mid 50s. Snow levels around 3000-3500 feet look to fall to around 1500-2000 feet tonight, so a few inches of snow look to be possible in and around the mountain passes, maybe locally heavier in and around the convergence zone as it drifts eastward. Weak troughing will linger into Tuesday as well as scattered showers and cooler temperatures (mid 50s). Most showers will most likely be confined to the mountains to due some orographic enhancement. Troughing will progress away from the area on Wednesday, leaving room for an upper level ridge in the NE Pacific to shift eastward closer to our area, bringing drier and warmer conditions into Thursday. Temperatures will begin to warm starting on Wednesday into the lower 60s, then into the mid 60s on Thursday. .LONG TERM /FRIDAY THROUGH MONDAY/...From Previous Discussion...Conditions continue to be warm and dry into Friday, with the ridge axis looking to move over western Washington. The exact location and intensity of the ridge continues to change, so uncertainty lies in how warm we get, but looks like mid to upper 60s is the best bet for Friday, with Friday looking like the warmest day of the week. Ensemble members continue to show a weak front that may brush the area into Saturday, which would allow temperatures to moderate some heading into the weekend with the possibility of some showers around. Warmer conditions still look to remain, with temps in the long term looking to stay in the upper 50s/lower 60s. Mazurkiewicz && .AVIATION...Generally VFR conditions in place over W WA this evening in the post frontal environment. Westerly to northwesterly flow will continue aloft. Latest radar shows convergence zone showers persisting across the central Sound this afternoon along with some scattered light shower activity along the coast. With continued onshore flow, expect convergence zone activity to linger into Tuesday morning. As such, lower cigs and a brief shift in wind direction will be possible for interior terminals along the central Sound at times within its vicinity. Outside of the CZ activity, may see some lower MVFR cigs redevelop overnight into early Tuesday morning - mainly for terminals along the southern Sound (KOLM). Overall conditions then look to rebound to widespread VFR by late Tuesday morning. KSEA...VFR conditions with southwesterly winds 4-8 kt,, although occasional shifts to the north will continue to be an issue as PSCZ activity continues. Associated showers remaining to the north of the terminal, but may sag southward overnight into early Tuesday bringing showers in the vicinity and ceilings down to MVFR at times. These CZ showers will taper Tuesday morning, with VFR conditions expected by Tuesday afternoon. 14/18 && .MARINE...Gusty onshore flow will continue in the wake of a frontal passage tonight, with gales expected through Admiralty Inlet and the Central and Eastern Strait of Juan de Fuca. Elsewhere, Small Craft Advisories remain in effect for portions of the coastal waters and for the West Entrance of the Strait through early Tuesday. Winds will ease Tuesday and high pressure builds into the coastal waters and interacts with lower pressure inland. This pattern will remain in place through much of the week for overall calmer conditions across the area waters. The next frontal system arrives over the weekend. Seas over the coastal waters continue to hover between 8 and 10 feet this afternoon and will gradually lower back towards 7 to 9 feet tonight into Tuesday. Seas will continue to subside through the week, trending below 5 feet Thursday and Friday. Seas will then increase towards 6 to 8 feet again over the weekend. 14 && .HYDROLOGY...No river flooding is expected through the next seven days. && .SEW WATCHES/WARNINGS/ADVISORIES... WA...None. PZ...Small Craft Advisory until 5 AM PDT Tuesday for Coastal Waters From Cape Flattery To James Island 10 To 60 Nm-Coastal Waters From Cape Flattery To James Island Out 10 Nm-Coastal Waters From James Island To Point Grenville 10 To 60 Nm- Coastal Waters From James Island To Point Grenville Out 10 Nm-West Entrance U.S. Waters Strait Of Juan De Fuca. Gale Warning until 5 AM PDT Tuesday for Central U.S. Waters Strait Of Juan De Fuca-East Entrance U.S. Waters Strait Of Juan De Fuca. && $$