A cool upper level low over the area will shift south this afternoon. Snow or a mix at times may produce additional accumulation over portions of the area this morning. Rain and snow showers over the area will gradually dissipate by midday. Mostly dry conditions over the weekend with a weak ridge of high pressure over the region. The next front arrives later monday and tuesday with breezy and wet conditions. Drier weather returns by the middle of next week.
Looking at both yesterday morning and this morning...it is unfortunately safe to say that spring is on back-order and will ship once it is back in stock. overnight saw the development of a convergence zone over snohomish county which left some snow for early risers and showers developing from the low crossing the area have brought accumulations to lewis...mason and kitsap counties as well as some coastal locations. with current temperatures still generally ranging from the upper 20s to the mid 30s...snow and/or mixed precip still looks to be on the table for the remainder of the morning. All that being said...inherited headlines for snow will be allowed to run their course. The radar trend for showers over lewis county shows activity decreasing while a second blob of activity over portions of mason and kitsap counties looks to be slowly chugging out of the area. hopefully by the time it crosses the sound and enters into eastern king county it will be mostly rain or...at the very least...will have weakened somewhat becoming either light snow showers or flurries with little to no additional accumulations by that point. will continue to monitor.
Incoming 12z data looks to be fairly consistent in the near term with showers becoming more scattered and tapering off as the day progresses and the low ejecting out of the area by this evening. Dry conditions still look to be a lock for saturday and sunday. For more detailed analysis...please refer to the previous discussion section below. smr
From previous discussion...a closed upper low over wa this morning is associated with a -38c cold pool aloft and a surface low feature just offshore. Latest msas analysis places a 1013 mb close surface low west of the central coast, which is generating a batch of instability showers moving into the southwest interior. 1000-850 mb thickness values near 1385m with steep lapse rates in the low levels and surface temperatures near freezing should keep showers in the form of snow for most the morning. Models differ on how quickly this activity shifts south, but given the upper low closing off over the area, showers may stick around through at least the morning commute. will need to monitor the progress of showers reaching inland but model precipitation amounts generally agree than light accumulations could reach up to the tacoma area but probably under an inch. A dusting of snow may reach the seattle metro area but most the showers will stay confined to the lower hood canal and sw interior to the central coast. The winter weather advisory was expanded to thurston and lewis counties with 1 to 2 inches of snow possible this morning in heavier showers. The low will drift south this afternoon and mixed rain/snow showers will gradually end.
High pressure is expected to build over the region this weekend with dry weather. There could be some patch fog, mainly in prone low lying valleys including olympia and shelton. Fog should not be widespread and temperatures will warm slightly during the day, but remain a bit chilly at night, near freezing in colder outlying areas. Mercer
From previous discussion...the extended forecast closely followers the ecmwf solution which brings a decent consolidated front into the area monday night and pushing east tuesday with a transition to showers. this looks like a garden variety front and is progressive, so river flooding is not expected to be an issue. Temperatures will be a bit milder and snow levels will keep any snow limited to the passes. Precipitation amounts are not terribly impressive and suggest a few inches of snow possible, but may not reach advisory level.
The trailing trough will shift east on wednesday with a gradual drying trend. High pressure builds over the pacific northwest with possible undercutting of the high in split flow keeping systems to our south. The middle to later part of next week appear to look dry with partial sunshine. Mercer
Mercer
River flooding is not expected for the next 7 days.
Wa...winter weather advisory until 10 am pst this morning for central coast-hood canal area-lower chehalis valley area-southwest interior.
Pz...none.
Gradients will be fairly light today. Moderate offshore flow will develop over the weekend. A front will move through the area monday and monday night, with small craft advisory strength winds likely over most waters. These winds will probably extend into tuesday. Westerly swells of 15 ft or so may reach the coast monday night and tuesday.
An upper low over washington is slowly shifting east. light flow aloft will become northerly tonight. Skies range from mostly clear in the northwest to cloudy around puget sound. Areas of fairly low cigs this morning will lift up into cumulus this afternoon. Skies will be mostly clear tonight.
Ksea...the radar at 9am shows that sea-tac will probably get a couple hours of snow, and then the precip ought to turn back to scattered showers for the middle of the day. By mid afternoon there ought to be pretty good sunbreaks, and then clearing is a good bet tonight as the cold upper low finally departs.