Such bitter cold following snowfall is rare, meteorologists say

Residents are feeling the cold today as temperatures dip into the single digits and wind chills plummet to minus 15 across the region. According to forecasters, colder temperatures following snowfall is typical for winter storm progression—but not this cold.

“This is as cold as I’ve ever seen it after a snowfall,” said WCVB-TV meteorologist Mike Wankum. “Why it’s this cold? We have no idea.”

National Weather Service meteorologist William Babcock said New England storms drag in cooler air from over Canada as they leave the region. “Sometimes that air is colder than during other storms,” he said.

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This week’s cold air mass caused temperatures to fall into the single digits, which played a role in the storm’s higher-than-normal snowfall.

“As the air gets colder the water content diminishes, and we start to see changes in the type of snow crystal, making the snow fluffier and take up much more area,” Babcock said.

Snow-to-water ratios are typically 10 inches of snow per one inch of water. In colder temperatures, that ratio goes up to 15-to-one and sometimes 20-to-one, he said.

This proved especially true for towns north of the Massachusetts Turnpike, where higher elevation and distance from the ocean’s temperature-moderating effects caused the area get more than two feet of snow by this morning.

“Even a one- to two-degree change in temperature can be enough to make precipitation lighter and accumulation higher,” Babcock said.

Essex County had the heaviest snowfall, partly due to some pre-storm snowfall.

“They had a little bit of moisture ahead of the snow, so they started with well over a foot of snow before the storm,” Wankum said.

The last time New England got this much snow was a blizzard last February, which dumped 30 inches in Fitchburg, 29 in Wilmington, and 28.2 in Saugus.