We are diving head first into a late winter, downstream blocked, -NAO pattern and even before we really hit the water, we are expecting some decent snowfall. Lots of questions in the longer range about how well we can optimize this more favorable setup, but the weather picture for the rest of this week has certainly attained more clarity and a Winter Storm Watch now covers all of central and northern Vermont.
The clipper system responsible for that bit of snow (1-3 inches) Tuesday evening will help bring colder air down from eastern Canada into northern New England. The very warm (relative to the season) Great Lakes aggregate is a feedback that has helped repel attacks of colder weather, but this particular airmass can work its way around that area of relative warmth and envelop much of Vermont more directly by Wednesday morning, and temperatures for much of the day should stay in the 20's under high clouds. There's been a lot of talk about the impressive temperature gradient over the eastern United States and this should begin to take shape on Wednesday and will help to fuel this expansive weather system which will be positioned near Chicago during the evening. This intense clashing of airmasses will help fuel the overrunning snowfall which will should begin within a few hours of 10 pm Wednesday and continue steadily and occasionally heavily during the overnight. The snow will become lighter and may stop altogether during the ski day, but at that point 8-12 inches of the good stuff will be on the ground with temperatures hovering around 20 degrees. Some of the higher resolution data has been clashing with the consensus already reached by global models involving the track of this storm. I've been pretty convinced the MRV is positioned in an optimal place for snowfall out of all this, but the higher res data has been poking the area with mid-level warmth because the storm is being simulated to track on a more northerly course. I've been reassured that this will not be a significant issue as of Tuesday afternoon, but a period of sleet is possible early Thursday though temperatures should remain well below freezing.
There is a 2nd piece of this storm which will bring more snowfall to the region Thursday evening. The heaviest snowfall in this time frame is likely to be closer to the Canadian border but the MRV is positioned to get an additional 1-3 inches during the evening and then as winds turn north to northwesterly early Friday, moisture from the unfrozen and very warm (for the season) Lake Champlain will bring an additional 1-3 inches of snowfall. Add all of this together and we have a 10-18 inch storm total (8-12 Wednesday night, 1-3 Thursday evening and 1-3 Friday morning). Friday and Saturday are setup to be chilly with temperatures holding in the lower teens Friday, falling below zero Friday night and climbing back into the teens Saturday. I want to promise the return of some sunshine but this is a very busy weather pattern and the weekend is likely to feature a lot of clouds and some additional light snow both days. Some light accumulations are possible but I don't see more than 3 inches.
Ensembles have become more aligned around the idea of a massive storm that would initially mature in the Upper Midwest, but duck under the strengthening downstream block and become a big rain and snow producer for all of New England, beginning as early as late Monday February 27th and extending into Wednesday, March 1. Operational models are throwing in a warm, rainier scenario or two and this appears most likely for coastal areas of New England. There is a history of storms in this type of setup to be terrific snow producers for the interior mountains and this event, about a week from now, has that kind of potential. As mild and as disappointing as this winter has been across eastern North America, I would still be surprised to see this storm turn into a rainmaker and would be more concerned about the track of this storm shifting south, farther underneath the blocking. Needless to say, this should have our attention in the days ahead as a storm that could prove to be the biggest of the season for us.
And the pattern might not be done after that with storminess indicated to continue into the first 10 days of March. Like many -NAO patterns, the temperature outlook doesn't look especially cold, but the pattern is supportive of additional chances for snowfall and there are growing indications of another potential event the first full weekend of March
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