Arctic blast to introduce coldest air so far this season to northern US

 By Courtney Travis, AccuWeather senior meteorologist

Updated Dec. 14, 2020 11:56 AM

Bursts of cold air are forecast across the northern tier of the United States this week, and one cold shot could help produce a snowstorm in the East.

First, a high pressure system that originated over western Canada from this past weekend is expected to push through the Great Lakes early this week, bringing with it a shot of cold air.

"While this air mass is not in any way extreme for December standards, it does represent a significant change from the very balmy weather of recent days," said AccuWeather Senior Meteorologist Joe Lundberg.

High temperatures soared to more than 20 degrees F above normal last week in cities like Minneapolis and Chicago while Billings, Montana, reached 64 degrees, almost 30 degrees above normal. So, even seasonable mid-December temperatures are likely to feel drastically different.

"Parts of Montana, the Dakotas and northern Minnesota can expect temperatures below normal for the start of the week, with single-digit morning temperatures and afternoon highs only in the teens and low 20s through Tuesday," added Lundberg.

Temperatures of this value will rival the cold snap that occurred in November.

In addition to the colder air, a brisk breeze will bring AccuWeather RealFeel® Temperatures to dangerous levels for a time.

On Monday night and early Tuesday morning, it will feel like it is below zero across the majority of the Upper Midwest and the northern Plains, with AccuWeather RealFeel® Temperatures nearing the single digits in places like St. Louis and Chicago.

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The cold air is forecast to slowly shift eastward across the northern tier of the country through the early part of the week, as a quick-hitting storm moving through the Northeast makes way for the colder air.

High temperatures on Tuesday will not rise any higher than the 20s across Upstate New York and northern New England.

The cold air in place across much of the Northeast by the middle of the week is forecast to set the stage for a major snowstorm and allow icy conditions to unfold across the mid-Atlantic and the Northeast.

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"As a strong high pressure strengthens across Quebec and northern New England Tuesday night and Wednesday, Arctic air will shift southward across the mid-Atlantic, allowing for a drop in temperature," explained Lundberg.

The storm will also help to pull down even more cold air down from Canada in its wake, creating the coldest conditions so far this season.

High temperatures are forecast to struggle to get out of the upper 30s on Wednesday and Thursday for major cities like Philadelphia and Washington D.C., while New York City and Boston may not even reach the freezing mark. Low temperatures are forecast in the teens and lower 20s on Thursday night.

The chill will linger across the eastern U.S. through week's end but lose some of it's intensity. At the same time, milder conditions will shift into the northern Plains.

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