This weekend, those in the Northern Plains and Upper Midwest could experience the country's coldest temperatures of the year. The East Coast should see a reprieve over the weekend, but bitter temperatures are expected to return Monday night.
Michael Wirtz/The Philadelphia Inquirer/AP
As they lean into their snow-shoveling for warmth, New Englanders might be wondering why a nor'easter that dumped more than a foot of snow across several Eastern states, left such exceptionally cold temperatures in its wake.
Winter storm Hercules, which hit the Eastern Seaboard between Thursday and Friday, was what meteorologists call "well organized," meaning that at least three major factors converged to produce a lot of snow and a lot of cold. An Arctic air mass descended through Canada and hit the warmer Atlantic, where the system both gathered moisture and sucked the water's warm energy upward – at just the same time that a jet stream arrived from Alaska, delivering turbulent, eddy-riddled air.
"The jet stream moves in response to temperature differences," explains Matthew Belk, a National Weather Service meteorologist. "Nature is always trying to restore balance with itself. Every bit of weather that we have is a result of an imbalance that was generated."
Temperatures on Friday rose no higher than 19 degrees F. in Philadelphia, 13 degrees in Boston, and 8 degrees in Portland, Maine, and the windchill factors prompted warnings about frostbite. Weather.com reported that Portland's temperature of plus 8 degrees "feels like" minus 8.