The coldest air this month will build across the Midwest and northeastern United States late this week and into the weekend and develop bands of lake-effect snow across the Great Lakes.
This shot of cold, but seasonable air will be a shock for many as temperatures have been well above average for most days since the beginning of November.
Many locations across the Midwest and Northeast are averaging near or more than 10 degrees above normal in terms of average temperatures this month through Dec. 15.
The jet stream will finally dip southward later this week into the weekend opening the door for colder air to build in from Canada.
"This will be a sharp contrast in air masses compared to the mild conditions over the last several days," AccuWeather Senior Meteorologist Matt Rinde said.
The jet stream is a zone of strong winds in the upper levels of the atmosphere that tends to separate the cold air to the north and the warm air to the south.
JUMP TO: Cold Air Builds Across Midwest, Eastern US| Lake-Effect Snow to Blanket Great Lakes
"After a very mild start to December, temperatures more typical of this time of year will be felt across the Midwest and Northeast Thursday into Saturday," AccuWeather Meteorologist Ryan Adamson said.
While this shot of air will feel cold for many, temperatures will actually be near or slightly below normal for this time of year.
Cold winds will cause AccuWeather Realfeel® temperatures to be in the teens and 20s across much of the region on Friday and Saturday.
"The core of the cold will focus on the Upper Midwest with temperatures likely to be held at or below freezing for at least two consecutive days from Chicago to Minneapolis and Fargo, North Dakota," AccuWeather Senior Meteorologist Krissy Pydynowski said. "For the latter city, temperatures may not climb out of the teens."
The coldest air will not arrive to the Interstate-95 corridor until Saturday.
Anyone heading to the local malls on the final weekend before Christmas will need to bundle up as you head outdoors.
This shot of cold air will be short-lived as a return to near-record warmth will be in store next week.
"Temperatures will moderate back to near-record levels by Christmas," Adamson said. "The mild air next week combined with rain should melt all of the lake-effect snow that falls this weekend."
Cold air moving over the unusually warm waters of the Great Lakes will generate bands of lake-effect snow on Friday into Saturday night.
The most organized bands of snow will form off the upper lakes of Superior and Michigan on Friday into Friday night and across lakes Huron, Erie and Ontario on Saturday into Saturday night.
Snow bands will be mainly oriented from west to east off the lakes. For the majority of the event, the bands will be outside some of the major cities of upstate New York including Buffalo, Syracuse and Watertown.
"The highest snowfall totals will fall downwind of lakes Erie and Ontario," Adamson said.
Snowfall totals across the Tug Hill Plateau in upstate New York could receive between 1 to 2 feet of snow by Sunday.
"Off of Lake Erie, Jamestown, New York, could see over a foot of snow by the time the snow ends on Sunday morning," Adamson said.
Travel will become dangerous across portions of interstates 196, 81, 86, 90, 94 and 96.
Those hoping to snowmobile or ski will have a day or two to enjoy the packed powder where the snow falls before a warmup will melt much if not all of the snow during next week.
Outside of any heavy snow band, snow showers and flurries will occur across most areas around the Great Lakes as well as the Appalachians. Snowflakes can be seen across Detroit, Cleveland, Pittsburgh and Buffalo, New York.
Buffalo will have the chance of receiving its first measurable snowfall of the season this weekend.