By James M. Arnold, Weather Specialist
Region – It is hard to believe that we are waiting for yet another plowable snow storm to visit central Massachusetts with the beautiful day in progress today. This is the kind of day some of the old timers referred to as a “weather breeder”. Clear blue skies and light winds are allowing temperatures to moderate a bit and help to melt a little of our deep snow cover. Our temperatures will top out in the low to mid 30s today, and this feels like a heat wave after the severe cold of recent weeks. Tonight will be clear, calm and cold, and temperatures will plummet to around zero to 10 above in most areas but those places that are usually subject to radiational cooling will see readings from zero to 10 below by Sunday morning. It was 6 below zero here in Shrewsbury early this morning.
As our next storm approaches from the west, clouds will increase during the day Sunday and light snow will break out in the Shrewsbury area during the mid to late afternoon. Light to occasionally moderate snow will continue throughout the night Sunday and into Monday morning before ending during the mid morning. Temperatures throughout the period will be in the low to mid 20s, so our snow will once again be of the light and powdery variety. There are some interesting variables with this system. The most important one is if and where does a weak secondary storm form along the coast. I think a weak circulation does develop just to the south of Long Island and while this will not become the most impressive storm we have seen this winter, it will help to keep the cold air in place and will throw a bit more moisture back over southern New England. All this will give central Massachusetts and indeed most of southern New England a pretty uniform and fairly substantial snow fall of 4 to 8 inches. There could even be some isolated totals of up to 10 inches reported. While there is a relatively small amount of moisture available to this system, once again the powdery nature of the snow (the fluff factor) will inflate totals to some degree. Even the coastal areas and the Cape will share in the snow this time, with the only places where a mix or changeover might occur would be the Islands and the outer Cape. Even there, some snow will fall before precipitation mixes with or changes to rain. Elsewhere along the coast snow and a wintry mix will likely be the rule. Wind will not be an issue for anyone with this storm.
As the storm passes on Monday morning and clearing sets in, what wind there is will shift to the northwest and usher in what else, more colder air. This air mass should only be about 8 to 12 degrees below averages, not as cold compared to averages as past air masses. The respite will only be short lived however, as clouds from the next system to approach us will arrive Tuesday morning. All indications are that this storm will try to move up the Saint Lawrence valley and try to drag warm air into our area. There are also some subtle signs that once again a weak coastal secondary storm will try to form south of Long Island. Were this to happen, its impact would be to hold cold air in at the lower levels of the atmosphere, at least delaying if not preventing a change to rain in inland areas. Although there are not many good scenarios with this storm the worst case would be for a prolonged period of a wintry mix, tending toward freezing rain, with ice collecting on trees and power lines. Should precipitation completely change to rain a different set of problems emerge, as urban and street flooding could become extensive, especially in the usual areas. As far as timing goes, (and this is still nearly 4 days away) it looks like snow will develop before midnight Tuesday night and continue for several hours before any changeover begins. Regardless of changeover timing and precipitation type, there will be a general snow accumulation of 2 to 5 inches before that happens. The lowest snow totals will be along the Route 495 corridor and south of the Mass Pike and these will increase to the west and north of these areas.
I will have more specifics on the Sunday night storm should anything change as it approaches and will have more information on the Tuesday night storm as it draws nearer to us.
James M. Arnold is a Weather Specialist working with Shrewsbury Emergency Management Agency; town of Princeton; Worcester Emergency Communications and Emergency Management Agency; Southborough Emergency Management Agency; town of Grafton and Wachusett Mountain Ski Area