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

Linda Lam
Published: December 5,2016
The record warmth that much of the U.S. experienced this fall will just be a distant memory this week. A change is arriving, courtesy of the first arctic blast of the season, engulfing the western states early in the week, then spreading east throughout much of the Lower 48 into next weekend.
(MORE: Record Warm Fall For Many Cities)
The pool of arctic air that is beginning 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.
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 then 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 will first be felt in the northern Rockies on Monday and will spread through much of the West and into portions of the northern and central Plains by Tuesday.
(FORECAST: Great Falls, Montana | Salt Lake City | Denver | Albuquerque, New Mexico)
The first sub-zero temperatures of the season for some locations are expected Tuesday through Thursday mornings from the Rockies to the northern Plains.

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.
(MORE: Multiple Shots At Snow In Midwest Ahead)

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 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, Cincinnati and St. Louis are among the cities where the mercury will plunge into the teens.

Forecast AM Low Temperatures

(MORE: The Coldest Temperatures Ever Recorded in Each State)
The chilly conditions will reach all the way to Florida. Temperatures in central Florida will 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 see freezing temperatures.

MORE: The Coldest City on Earth