000 FXUS66 KSEW 190947 AFDSEW Area Forecast Discussion National Weather Service Seattle WA 247 AM PDT Tue Mar 19 2024 .SYNOPSIS...A weakening upper level ridge will provide one more dry and mild day for Western Washington on Tuesday. A weak upper trough will produce some light precipitation across the region later Wednesday into Thursday. A deeper trough and associated frontal system will produce more widespread precipitation Friday into the weekend along with snow levels falling to many of the passes. && .SHORT TERM /TODAY THROUGH THURSDAY/...Mostly clear skies prevail across Western Washington early this morning as upper ridging remains in control. The only exception is a shallow marine layer along the central coast. Similar temperatures to Monday are expected across interior areas today, but increasing onshore flow will produce several degrees of cooling along the coast. The ridge will weaken and shift eastward tonight as a weak upper trough approaches the area. Clouds will increase and temperatures will cool several degrees on Wednesday, but little in the way of QPF is expected until Wednesday night when the trough shifts onshore. A frontal system stalling offshore will spread additional light precip across Western Washington on Thursday along with continued cooler temperatures. .LONG TERM /FRIDAY THROUGH MONDAY/...More significant precipitation is expected to spread across the area on Friday as a deepening upper offshore pushes a front onshore. Showery and cool weather is expected over the upcoming weekend as the trough gradually shifts onshore. Snow levels will creep downward as well...likely to most of the passes by Saturday night into Sunday. Unsettled conditions are likely to continue into the early part of next week, but confidence is low in the details. Ensemble means place the region in northwest flow aloft Sunday into Monday as broad upper troughing takes up residence over the western lower 48. This leaves Western Washington susceptible to a system or two slipping southward down the British Columbia coast. One thing is for sure, the unseasonably mild and dry conditions aren`t returning anytime soon. 27 && .AVIATION...Upper-level ridge overhead with southwest flow aloft. Fog and low stratus currently hugging the coast as HQM is under LIFR conditions. Most fog should remain here but can`t rule out patches developing over parts of the interior as the morning progress. Mostly VFR elsewhere throughout the day but, low stratus and fog looks to spread further inland tonight with a better chance for more widespread MVFR to LIFR ceilings and vis. KSEA...VFR currently with light northerly winds at the surface. Slight chance (15%) of LIFR fog between 12-16z this morning but VFR should be at play most hours of today. Light winds at the surface will increase out of the SW later this evening after 00z between 5- 10 kt as stratus draws near late overnight. McMillian && .MARINE...Onshore flow along with weak troughing at the surface. Relatively benign conditions are expected today before a weak low center enters tomorrow. However, no impacts are expected with sub- advisory conditions likely. Seas less than 10 feet through the week, mainly in the 3-6 ft range. A weakening front is probable to arrive over the weekend with the next best chance of SCA winds over the coastal waters. McMillian && .HYDROLOGY...No river flooding is expected over the next 7 days. && .SEW WATCHES/WARNINGS/ADVISORIES... WA...None. PZ...None. && $$
NWS SEW Office Area Forecast Discussion
Discussion Script by Ken True at Saratoga Weather - WFO Script by SE Lincoln Weather