First Arctic Blast of the Season Arriving as Pattern Change Brings Colder Temperatures from Coast to Coast

Linda Lam
Published: December 6,2016
The record warmth that much of the U.S. experienced this fall is abruptly coming to a halt this week. A change is setting in, courtesy of the first arctic blast of the season, which has already engulfed the western states and will continue to spread east throughout much of the Lower 48 into the weekend.
(MORE: Record Warm Fall For Many Cities)
The pool of arctic air that has begun to invade the Lower 48 originated in Alaska and northwestern Canada.
Parts of Alaska saw frigid conditions over the weekend, with lows dipping to minus 36 degrees in Fairbanks on Sunday. Though very cold, it's still quite far from their daily record of minus 53 degrees for the day. Arctic Village, Alaska, saw their temperature dip to minus 42 degrees Sunday.
(MORE: Frigid Cold -30s and -40s Descend Into Alaska)
A pattern change has now dislodged that arctic air, allowing it to spill southward in the days ahead.

Current Temperatures

Specifically, a southward dip in the jet stream, or upper-level trough, that originated in the Gulf of Alaska and western Canada is now slipping into the western U.S., and will continue to slide eastward as the week progresses. High pressure at the surface is also diving southward, allowing arctic air to spread into parts of the Lower 48.
(MAPS: 10-Day Forecast)

24 Hour Temperature Change

This is the first arctic air mass of the season for the U.S., just in time for the first full week of December.
(MORE: December Temperature Outlook)

How Cold Will It Get, and When?

Big temperature drops are anticipated, with highs and lows falling 20 to 30 degrees.
These very cold conditions were first felt in the northern Rockies on Monday and are now spreading through much of the West and into portions of the northern and central Plains.
(FORECAST: Great Falls, Montana | Salt Lake City | Denver | Albuquerque, New Mexico)
The first sub-zero temperatures of the season for some locations are expected through Thursday morning, from the Rockies to the northern Plains. Great Falls, Montana, dipped below zero late Monday night for the first time this season and Cut Bank, Montana, saw sub-zero temperatures early Tuesday morning.

Forecast Morning Lows

High and low temperatures will be as much as 30 degrees colder than average. This translates to high temperatures below freezing for much of the West and into the northern and central Plains and Midwest. In fact, highs may hold in the single digits midweek in parts of the northern Rockies and northern Plains.
Even with these very cold temperatures, widespread record lows are not expected.
(FORECAST: Bismarck, North Dakota | Omaha, Nebraska | Chicago | St. Louis)
It will be windy, as well, which will make it feel even colder than what the thermometer reads, resulting in brutal wind chills.
In addition, snow will accompany the cold temperatures in some locations, including the northern Plains.

Forecast Highs Compared To Average

Arctic air will continue to plunge through the Plains and into the Midwest midweek. Above-average temperatures will be replaced with below-average readings. Highs will drop from the 40s to the 20s for much of the Midwest.
Late in the week, the colder conditions will reach the East Coast.
(FORECAST: New York | Washington, D.C. | Atlanta | Orlando)
At this time, it appears that temperatures will not be as cold for the East as for the West and Plains. However, it will feel much more like winter.

This Week's Forecast

High temperatures will drop from the mid-40s to the low to mid-30s for much of the Northeast, and many areas of the South will see highs in the 50s and 60s replaced with highs only in the 30s and 40s.
Many areas in the South will experience a hard freeze late this week with lows dipping well into the 20s, including Atlanta, Nashville and Raleigh.
The Ohio Valley, southern Great Lakes and mid-Mississippi Valley will see lows crash into the teens later this week. Chicago, St. Louis and Columbus, Ohio, are among the cities where the mercury will plunge into the teens.
(MORE: The Coldest Temperatures Ever Recorded in Each State)

Forecast Morning Lows

The chilly conditions will reach all the way to Florida. Temperatures in central Florida may only reach the upper 50s or low 60s Friday, compared to 80s early in the week. Lows in the 40s may push into the central Florida peninsula, including Orlando, by Saturday morning. The Florida panhandle will likely see freezing temperatures.
In fact, forecast model guidance over the past few days has been suggesting all 50 states will include an area that is below freezing Saturday morning.

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Brian Donegan ✔ @WxBrianD

The GFS continues to suggest all 50 states will include an area that is below freezing Saturday morning (Hawaii and Alaska not shown). #cold

8:04 PM - 6 Dec 2016

Interestingly, this tends to happen multiple times virtually every winter behind an arctic cold front, so it is not as unusual as you may think.
(MORE: 5 Things to Know About Arctic Cold Fronts and the Plummeting Temperatures They Produce)

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