Area Forecast Discussion
Issued by NWS Seattle/Tacoma, WA

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000 FXUS66 KSEW 041223 CCA AFDSEW Area Forecast Discussion...CORRECTED National Weather Service Seattle WA 423 AM PST Thu Mar 4 2021 .SYNOPSIS...Slow moving frontal system offshore will approach the coast tonight and move through Friday afternoon. Upper level trough moving across the area Friday night and Saturday morning. Next system arriving Sunday. Upper level low offshore Monday moving south into Wednesday pulling systems south of the area for the first half of next week. && .SHORT TERM /TODAY THROUGH SATURDAY/...Satellite imagery shows frontal system well offshore with mid and high level clouds spreading over Western Washington early this morning. Temperatures at 3 am/11z were mostly in the 30s. Frontal system offshore slowly moving east today with the leading edge of the precipitation ahead of the front spreading over most of the area in the afternoon. Increasing mid and high level moisture this morning could result in some lenticular clouds around Mount Rainier. Slow moving/stalling front offshore good recipe for a warm day this time of year but with the thicker cloud cover already near the coast and spreading inland this morning will keep highs in the 50s. Front stalling near the coast tonight with the large upper level trough offshore between 130 and 140W digging south. Front close enough to give the entire area precipitation overnight. Snow levels rising to 4000 to 4500 feet tonight. Easterly cross Cascade gradient not very strong, -4 or -5 mb, so do not expect any cold air to get trapped in Stevens or Snoqualmie pass. Only snow in the passes near the summit of White Pass. Breezy conditions over the northern portion of the area with southerly winds gusting as high as 40 mph. Lows Friday morning in the mid 40s. Rain continuing Friday with the cold front finally moving through Western Washington later Friday afternoon. Winter weather advisory for the Olympics beginning this morning will come to an end late Friday morning. 6 to 15 inches of new snow possible at Hurricane ridge by late Friday morning. In the Cascades, snow levels remaining above the passes. Air mass destabilizing quickly behind the front with thunderstorms possible along the coast late in the day. Highs Friday around 50. Upper level trough offshore Friday night with the trough axis near the coast by early Saturday morning. Precipitation decreasing rapidly behind the front with just scattered showers across the area. Still a chance of thunderstorms along the coast in the evening. Lows Saturday morning in the mid 30s to lower 40s. Trough axis moving through Western Washington Saturday morning keeping a chance of showers in the forecast especially in the morning. Showers will become confined to the higher terrain in the afternoon. Highs Saturday a little on the cool side, mid 40s to lower 50s. .LONG TERM /SUNDAY THROUGH WEDNESDAY/...Extended models and ensemble solutions in good agreement with another front moving through Western Washington Sunday. Snow levels in the Cascades will be down around 2000 feet for snow in all the passes. Good agreement in the extended models continues into the first part of next week with a large vertically stacked low moving south off the west coast Monday through Wednesday. Ensemble solutions have a few members, less than 20 percent, with light precipitation. Model blend gives slight chance pops through the period. With some good consistency in the models at this point going to go dry for the most part Monday through Wednesday and keep the slight chance of showers wording just over the southern portion of the area at times. Highs will continue to be a little below normal, a couple of degrees either side of 50. Felton && .AVIATION...Southwesterly flow aloft with an upper level ridge to the east and a frontal system moving close to the coast this morning hours. Breezy conditions expected this afternoon. Breezy southerly winds return to Puget Sound by Saturday before tapering off into Saturday evening. Increasing clouds today as the frontal system approaches the coast. Patchy fog will also likely return this morning with visibility 1-3sm over the Southwest Interior and the Kitsap peninsula until approximately 18z. Rain beginning across Puget Sound between 00-03Z. KSEA...Southerly winds continuing through the day, generally between 5-10 knots. Increase in cloud coverage expected as the frontal system nears the area. Rain likely beginning at the terminal between approximately 02-04z this afternoon. Kristell && .MARINE...A vigorous cold front will arrive later today and slowly move through the waters into Friday. Winds across area waters will increase throughout the morning, with gales expected offshore. Offshore swells will remain elevated, between 13-16 feet, into Friday morning before decreasing Saturday. Another swell train will arrive on Sunday. A number of marine headlines are posted for area waters today and into Friday evening, including offshore gale warnings, and Small Craft Advisories for much of in the inland waters. Additional marine headlines may be posted Sunday into early next week as the unsettled pattern continues. Kristell && .HYDROLOGY...Stalling front offshore will keep precipitation going in the Olympics this afternoon through Friday afternoon. Snow levels rising to about 4000 feet. Rainfall amounts in the 24 hour period along the south slopes of the Olympics in the 2 to 3 inch range. It is possible that the Skokomish River near Potlatch reaches flood stage Friday morning. Will upgrade the hydrologic outlook to a flood watch for Mason county with the morning forecast package. Any flooding that does occur is expected to be minor. Felton && .CLIMATE...On this day back in 1955 Seattle experienced its coldest March day on record. With 5 inches of snow on the ground the low was 11 degrees, coldest temperature recorded in March in Seattle. The high was also the coldest on record for March, 29 degrees. Felton && .SEW WATCHES/WARNINGS/ADVISORIES... WA...Winter Weather Advisory from 10 AM this morning to 10 AM PST Friday for Olympics. PZ...Gale Watch from late tonight through Friday evening 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-Coastal Waters From Point Grenville To Cape Shoalwater 10 To 60 Nm-Coastal Waters From Point Grenville To Cape Shoalwater Out 10 Nm. Small Craft Advisory until noon PST today 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-Coastal Waters From Point Grenville To Cape Shoalwater 10 To 60 Nm-Coastal Waters From Point Grenville To Cape Shoalwater Out 10 Nm. Gale Warning from noon today to 10 PM PST this evening 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-Coastal Waters From Point Grenville To Cape Shoalwater 10 To 60 Nm-Coastal Waters From Point Grenville To Cape Shoalwater Out 10 Nm. Small Craft Advisory until 4 PM PST Saturday for Grays Harbor Bar. Small Craft Advisory from 6 AM this morning to 7 PM PST Friday for Admiralty Inlet-East Entrance U.S. Waters Strait Of Juan De Fuca-Northern Inland Waters Including The San Juan Islands. Small Craft Advisory from 6 AM this morning to 4 PM PST Friday for West Entrance U.S. Waters Strait Of Juan De Fuca. Small Craft Advisory from 4 AM to 10 AM PST Friday for Central U.S. Waters Strait Of Juan De Fuca. && $$ www.weather.gov/seattle

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