A cold front moved across eastern New York and western New England on Wednesday, December 10th, ushering in a cold airmass into the region. A low pressure system developed over the southeast states Wednesday and Wednesday night. This storm then headed northeast Thursday and Thursday night, December 11th, with precipitation spreading northward well in advance of the low. The low continued to track northeast, passing over the mid Atlantic region late Thursday night, and over the New York City Metropolitan area and southern New England Friday morning, December 12th. The low then moved to the Canadian Maritimes Friday night.
As the storm approached, warmer air moved in aloft, and with a cold airmass remaining in place at the surface, this set the stage for a significant mixed precipitation event. The precipitation came down heavy at times, especially Thursday night. Hourly precipitation rates of one quarter to one third of an inch were reported for several hours in the form freezing rain across much of the region. The precipitation changed back to snow before ending early Friday afternoon.
Total liquid amounts of 1 to just under 4 inches fell across Berkshire County. This heavy rain led to moderate flooding on the Green River near Great Barrington, as well as widespread ponding of water, especially in urban and low lying areas due to ice blocking storm drains.