With a slow start to the snow season for most of the Northeast, I'm not surprised to hear lots of questions about specifics for a potential Sunday/Monday storm already. With no time wasted, several of you have asked about specific amounts for your town, or your part of New England! I hear ya. Of course, I know it won't really surprise you when I say..."It's too early to know." A frustrating answer, I know, but those of you who follow my forecasts know I will always give you the honest assessment, whether that is one of confidence or lack thereof.
So...let's start with the numbers. Overall predictability for the Sunday/Monday timeframe is approximately 20-40%. Essentially, this means of all the potential solutions, the most agreement you'll find on any one solution is either side of 30%. That's not very good! Having said that, the probability that a storm will develop somewhere along the Northeast U.S. coast is quite high. So, what do these two statements mean? They mean, mutually, that I'm confident a storm will develop in the Northeast United States Sunday into Monday, but storm track has yet to be determined.
As you might imagine, with only about 30% predictability, this means there is a huge spread in potential storm tracks - from a track south of New England that delivers a healthy, mostly-snow storm to Southern New England excepting the immediate coastline, to a track along the Canadian border that brings perhaps a burst of snow or mix for all, then a change to rain for most. As you might expect, I think neither of these outliers will verify. Rather, the truth likely lay in the middle - a storm center that cuts over or very close to Southern New England later Sunday into Monday. What this would produce is a potential burst of Sunday/Sunday night snow and wintry mix, even in Southern New England, then a change to rain south. It is too early to predict how much wintry precipitation would come on the front end, but with dewpoint temperatures currently forecast to be in the upper teens or lower 20s, that would represent a relatively cold, dry air that possibly could support at least a couple of inches of snow, particularly for interior communities (tougher near the coast this early in the season), before any changeover. In Northern...and even Central New England, perhaps as far south as Southern NH and Northern MA...there is certainly the potential for a more prolonged period of snow to mix, and even perhaps all snow for some, particularly in the North Country.
Favorable parameters for snow certainly include ample moisture and a healthy surge of warm and moist advection slamming into an antecedent cold and dry airmass with low dewpoints surface through 10,000 feet. Unfavorable factor is - at this point - the forecast for a weakening and withdrawing anticyclone (high pressure) over Eastern Canada. For New England snow events, you want to see the high a little farther east, and at least holding its strength. It's for this important reason, coupled with a jet stream pattern that favors retreating cold and surging warmth, that I'm supportive of a storm track either cutting across New England, or too close to the South Coast to support an all-snow event for Southern New England. But, remember! It's 30% predictability at this point, so there's plenty to sift through in coming days.