A cool upper level low over the area today will weaken tonight and shift east of the area on friday. Mostly dry conditions over the weekend with a weak upper level ridge over british columbia and northeasterly flow aloft over western washington. Next front arriving later monday with the trailing upper level trough over the area on tuesday.
Current radar shows that bulk of snow activity east of puget sound continues to push north and weaken...now mostly confined to snohomish and skagit counties. activity for the remainder of w wa this morning is more scattered. current temps still hovering in the low to mid 30s...with obs ranging from 32 to 36 at most sites. All of this factors into current winter weather advisory in place. Given scattered nature of activity along the coast...will likely let that portion expire at 10 am pst. Some uncertainty when it comes to the portion of the advisory that deals with the lowlands east of puget sound. Although much of the snow activity is exiting the advisory area as already stated above...temps remain generally right around freezing there. essentially...this is one vote for keeping it in place til noon and one vote for possibly taking it down early...maybe right around the expiration of the coastal advisory. Still...given how this so-called spring has gone so far...will opt on the side of caution and likely leave second portion of advisory in place for the time being.
Incoming 12z gfs remains pretty consistent with previous runs. Will await 12z ecmwf before going too in-depth with analysis. That being said...given this consistency...thoughts not too different from previous shift and will defer to their thinking for remainder of this discussion. smr
From previous discussion...low level onshore flow increasing later this morning into this afternoon. This will raise the snow level up to around 1000 feet. Shower activity will decrease as well. Another cool march day in store with highs only in the lower 40s.
Upper level low moving over western washington overnight and weakening by morning. Low level onshore flow weakening with snow levels dropping back down under 500 feet by early friday morning. With the low weakening shower activity will become spotty and light overnight with the exception being a possible convergence zone over snohomish county. Lows friday morning will be in the upper 20s to mid 30s.
Upper level low slowly drifting east on friday with the flow aloft becoming northerly late in the day. With the low still hanging around will have to keep a chance of showers in the forecast. Snow levels will remain low, 500 feet or less for most of the day, with the lack of any onshore flow. Highs once again will only be in the lower to mid 40s.
Upper level low remaining over eastern washington friday night into saturday. Flow aloft becoming northeasterly as a weak upper level ridge builds into british columbia. Spotty showers will come to an end on saturday. Snow levels will remain low, less than 1000 feet, but significant accumulations are not expected. Lows friday night in the mid 20s to lower 30s. Highs on saturday in the 40s. felton
From previous discussion...extended models in good agreement with a dry day on sunday. Still some timing differences for the onset of the precipitation on monday but both the gfs and ecmwf are wet by monday night. Cool upper level trough moving through on tuesday. Both models have a ridge on wednesday with the ecmwf showing more amplitude to the ridge versus the gfs but even the gfs has a couple of dry days in the middle of next week. Temperatures will remain below normal through the period. Felton
River flooding is not expected for the next 7 days.
Wa...winter weather advisory until noon pst today for bellevue and vicinity-east puget sound lowlands-everett and vicinity- seattle and vicinity-tacoma area.
winter weather advisory until 10 am pst this morning for hood canal area-lower chehalis valley area-north coast-southwest interior.
Pz...small craft advisory until 4 am pst friday for coastal waters from cape flattery to james island 10 to 60 nm-coastal waters from james island to point grenville 10 to 60 nm- coastal waters from point grenville to cape shoalwater 10 to 60 nm.
Onshore flow will increase somewhat today as an area of low pressure moves onshore. Advisory level winds are expected over the outer coastal waters into tomorrow. Onshore flow will then weaken on friday. Weak offshore flow will return over the weekend before a frontal system brings advisory strength southerly winds to most of the waters on monday. 27
Westerly flow aloft will continue today and tonight as an upper level low over vancouver island moves weakens and moves east. Southerly and onshore surface winds are expected through the period. The air mass is moist and slightly unstable.
Snow has mostly ended from king county south, but is still falling north of king county. That snow will move out of the area in the next few hours. Scattered showers of mostly rain will follow this afternoon. Scattered showers will continue tonight and these could be snow showers, dropping an inch or less in spots at times. ceilings will continue to be mvfr/ifr through the morning, then become generally mvfr with occasional vfr through the afternoon.
Ksea...snow seems nearly done. Scattered rain showers this afternoon. Ifr ceilings and visibilities will improve to vfr by noon or so, then fall to mvfr tonight. Southerly wind 7-12 kt. Chb