Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

Current Version | Previous Version | Text Only | Print | Product List | Glossary Off
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28
-- Highlight Changed Discussion --
-- Discussion containing changed information from previous version are highlighted. --
000 FXUS66 KSEW 301619 AFDSEW Area Forecast Discussion National Weather Service Seattle WA 919 AM PDT Thu Mar 30 2023 .SYNOPSIS...
-- Changed Discussion --
A weak upper level trough will move across the region late today, bringing a chance of showers to portions of western Washington. A unseasonably strong frontal system will then move across the area Friday night into Saturday, bringing gusty winds, lowland rain, and periods of heavy mountain snow to the area. Cool upper level troughing will remain over the region into early next week for continued shower activity and below normal temperatures.
-- End Changed Discussion --
&& .SHORT TERM /TODAY THROUGH SATURDAY/...
-- Changed Discussion --
Satellite imagery shows low clouds along the coast and over the Lower Chehalis Valley and central Puget Sound with high clouds over the central and southern Cascades. Temperatures at 9 am/16z were in the lower to mid 40s. Northwesterly flow aloft today and tonight with a weak upper level trough moving through late this afternoon/this evening. Can`t rule out a few showers with the trough but for the most part it will be dry. Main weather producer in the next week is a unseasonably strong cold front that will reach the coast Friday night and move inland early Saturday. Rain, mountain snow and breezy conditions ahead and with the front. Winter storm watch is up for the Cascades beginning 00z Saturday for snow in all the passes. Cold, unstable air mass settling over Western Washington behind the front later Saturday keeping showers in the forecast. Current forecast looks good this morning. No updates. Felton .LONG TERM /SUNDAY THROUGH WEDNESDAY/...Previous discussion follows. Cool and unsettled weather will persist through much of the extended period. An upper level low looks to swing through the region Sunday into Monday, which will keep shower activity in the forecast. With a cold airmass remaining in place, snow levels will be rather low (between 400-600 ft) by early Monday morning. Should enough moisture linger for any heavier shower activity, cannot rule out a rain/snow mix for some lowland locations during the early morning hours. Temperatures will remain unseasonably cool Sunday and Monday, with highs generally in the 40s to low 50s and overnight lows expected to dip into the low to mid 30s. The upper level low looks to exit the Pacific Northwest to the south and east on Tuesday and looks to be replaced by an upper level ridge building into the region near midweek. The GFS and ECMWF ensemble solutions continue to show a reduction in the number of wet solutions for the period, but do still have 20-30 percent of the solutions showing some light precipitation. Thus, showers remain in the forecast for both days for now, but do not expect conditions to be as wet as over the weekend. Afternoon highs will warm a few degrees each day - and will be in the 50s. Overnight lows look remain in the 30s. 14
-- End Changed Discussion --
&& .AVIATION...
-- Changed Discussion --
Light northwesterly flow aloft will transition more westerly tonight as an upper trough moves towards the area. MVFR low clouds have spread into portions of the central Puget Sound this morning with onshore flow. Slow improvement to VFR expected for most areas in low clouds later this morning into the early afternoon. MVFR may linger for the immediate coast. A few light rain showers will be possible today mainly along the coast. MVFR cigs are likely again later tonight into Friday with increasing rain potential and breezy winds on Friday. KSEA...MVFR cigs this morning with onshore flow. Cigs will improve to VFR later this morning into the early afternoon. VFR this evening with MVFR likely later tonight into Friday. Southwesterly winds generally 7 to 12 kts. JD
-- End Changed Discussion --
&& .MARINE...
-- Changed Discussion --
Onshore flow through today with the strongest winds through the central portions of the Strait of Juan de Fuca, a Small Craft Advisory is in effect for this area. Increasing southerly winds on Friday as a frontal system moves towards the area. Small Craft Advisory winds are likely over all the waters Friday afternoon into Friday night, a slight chance for gales across portions of Admiralty Inlet and the Eastern Strait of Juan de Fuca. Winds will remain elevated through the weekend with onshore flow. Seas of 4 to 6 feet today will subside to 2 to 3 feet on Friday, building into Friday night and Saturday. JD
-- End Changed Discussion --
&& .HYDROLOGY...
-- Changed Discussion --
No river flooding expected in next 7 days.
-- End Changed Discussion --
&& .SEW WATCHES/WARNINGS/ADVISORIES... WA...Winter Storm Watch from Friday afternoon through Sunday afternoon for West Slopes North Cascades and Passes-West Slopes North Central Cascades and Passes-West Slopes South Central Cascades and Passes. PZ...Small Craft Advisory until 11 PM PDT this evening for Central U.S. Waters Strait Of Juan De Fuca. Small Craft Advisory until 11 AM PDT this morning for East Entrance U.S. Waters Strait Of Juan De Fuca. && $$

USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.