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Summary: A vigorous upper-level disturbance has generated an “Alberta Clipper” surface low pressure system which is presently moving rapidly southeastward across the Great Lakes. It is producing a band of moderate to heavy snow across Minnesota and Wisconsin. As the trough in the jet stream containing the disturbance digs south of us tomorrow, the disturbance will produce significant divergence in the jet stream wind flow over New England. This will result in pronounced upward movement in the atmosphere leading to a rapid deepening of the surface low as it moves off the southern New England coast and increasing instability due to the difference in temperature between the warm water at the surface and the cold air aloft associated with the upper-level disturbance enhances the upward motion.

With these types of systems it is always difficult to forecast snow amounts for Berkshire County because it is very difficult to time the intensification of the surface low relative to the western extent of the precipitation shield. The most likely total snow accumulation is 2-4″ but I wouldn’t be surprised to see the precipitation shield move to our east while most of the county is still in the lower end of that range. It will be cold, so the snow should be of the light and fluffy variety.

The timeline looks like this: Weak high pressure will build in overnight Monday generating ideal radiational cooling conditions with clear skies, calm winds and a fairly fresh snow cover. Low temperatures will reach well down into the single digits, near zero or even a few degrees below zero over the elevated terrain. Snow should overspread the region Tuesday morning between 9-11 am and be moderate at times for several hours, into the early to mid afternoon. Snow should then taper off during the course of the afternoon but may continue to fall moderate at times into the evening in the eastern highlands of the county.

We will then shift to a more mild regime as the week progresses as the jet stream shifts to the north as a trough digs over the western U.S.. If you are a snow lover, get out and enjoy it soon because it looks like we may end up with light mixed precipitation and rain on Friday and then, quite mild over the weekend and, possibly, a rainstorm late in the weekend and into early next week.

Monday Night

Clear, calm and very cold. Becoming overcast near daybreak.

Low temperatures generally in the low to mid single digits above zero, mid to upper single digits in South County. Near zero over the elevated terrain.

Northwesterly winds at 5-10 mph this evening, becoming calm after midnight.

Tuesday

Overcast and cold, with snow developing across the county between 9 and 10 am. Snow continuing, moderate at times until early to mid afternoon, then tapering off. The moderate snow may continue toward evening in the eastern highlands. Total snow accumulation 2-4″. Probability of precipitation near 100%.

High temperatures in the mid teens in Pittsfield, Adams, NorthAdams and Williamstown; mid to upper teens in Lee, Stockbridge, Great Barrington and Sheffield and; low teens over the elevated terrain.

Easterly winds increasing to 10-15 mph in the morning, shifting to northeasterly during the afternoon.

Tuesday Night

Mostly cloudy with any snow tapering off in eastern sections during the evening. An additional 1″ is possible over east facing slopes. Chance of a flurry during the remainder of the night.

Temperatures holding steady in the low to mid teens.

Northeasterly winds shifting during the evening to northwesterly at 8-12 mph.

Wednesday

Mostly cloudy during the morning, partial clearing during the afternoon, becoming partly cloudy late. Quite breezy.

High temperatures in the mid 20s in Pittsfield, Adams, NorthAdams and Williamstown; mid to upper 20s in Lee, Stockbridge, Great Barrington and Sheffield and: low 20s over the elevated terrain.

West-northwesterly winds at 10-20 mph with gusts up to 30-35 mph.