November 8, 2014 - NORTH AMERICA - Arctic air associated with the polar vortex will lunge into the North Central United States early next week and will expand southward and eastward to affect about 250 million people as the week progresses.
The polar vortex is a large pocket of very cold air, typically the coldest air in the Northern Hemisphere, which sits over the polar region. Occasionally, this pocket of very cold air can get dislodged farther south than normal, leading to cold outbreaks in Canada and the U.S.
The coldest weather of the season so far will extend from the Dakotas to Texas and the Interstate-95 corridor by the end of the week. The outbreak of arctic air will be long-lasting and may linger well past the middle of the month.
The worst of the cold will be felt from Fargo, North Dakota, and Minneapolis to Chicago and St. Louis.
According to AccuWeather Chief Meteorologist Elliot Abrams, "The arctic blast will have the greatest shock over the Central states."
People over parts of the Plains may experience a temperature plunge of 40 degrees or more following high temperatures this weekend.
The combination of cold air, wind and other conditions, including snow in part of the Midwest and northern Plains, will send AccuWeather RealFeel® temperatures plunging into the single digits and teens. Actual high temperatures may not reach the freezing mark in portions of the northern Plains and Midwest. Such cold will raise the risk of hypothermia and frostbite for those not properly dressed.
December-like cold will be felt farther along in the South and along the Atlantic Seaboard. The cold will rush into the South Central states by the middle of next week, but will not reach the Atlantic coast until later next week and into next weekend.
RealFeel Temperatures in these eastern areas will dip into the 20s and 30s and will make it uncomfortable for many outdoor activities.
According to AccuWeather.com Long Range Expert Paul Pastelok, "Temperatures will plunge to 20 degrees below average in parts of the South."
In New York City, it is possible temperatures may not get out of the 30s on one or more days from late next week into next weekend.
The action of cold air passing over the relatively warm waters of the Great Lakes will unleash bands of lake-effect flurries, snow and squalls from the Upper Midwest to the interior Northeast.
In addition to lake-effect snow, one and possibly two storms will accompany the advance of cold air.
The first storm will produce a band of snow from the northern Rockies to the Great Lakes early in the week.
A second storm could affect part of the East late next week.
WATCH: Michio Kaku - "Bombogenesis" - How the impending Arctic blast will unfold.
Despite the potential for localized snowfall, the cold air over much of the Plains to the East will advance over bare ground.
The bare ground and warm Great Lakes waters will take away some of the severity of this early season arctic outbreak.
Despite the moderation, freezing temperatures are possible in parts of the South and East that have not yet had such temperatures this season. People are urged to winterize vehicles and plumbing before the winterlike temperatures arrive.
Travel-Disrupting Snowstorm to Target Calgary, Minneapolis
Before the snow reaches the U.S., accumulating snow will spread from central British Columbia to central and southern Alberta on Saturday night through Sunday.
A total of 8 to 15 cm (3 to 6 inches) is in store for Calgary with higher amounts in the mountains and locations to the east.
The storm will move on to affect parts of Montana and Wyoming with snow, plunging temperatures and dangerous travel conditions on Sunday through Monday. High winds will howl, causing blowing snow and white-out conditions in some areas.
Also spanning Monday and Tuesday, the storm will turn farther east and could affect some major cities in the Midwest or at least connecting highways with snow.
The swath from South Dakota and southwestern North Dakota to central Minnesota, northern Wisconsin and northern Michigan are at greatest risk for several inches of snow.
The heaviest snow zone currently encompasses the cities of Aberdeen, South Dakota, Minneapolis, and Wausau and Green Bay, Wisconsin.
However, a shift in track of the storm by a couple of hundred miles could put the heavy snow zone over Fargo, North Dakota, and Duluth, Minnesota, or to the south over Sioux Falls, South Dakota, and Milwaukee, Wisconsin.
Portions of highways that may be impacted by snow and slippery travel in the Central states include interstates 25, 29, 35, 75, 80, 90 and 94.
The snow will initially melt as it falls on roads but is likely to create slushy and slippery conditions as temperatures tumble with advancing arctic air and the southward dip of the polar vortex.
Temperatures will plunge below freezing during and shortly after the storm. Parts of the northern Plains may experience temperatures dipping into the single digits and teens.
People can keep up to date on the developing snowstorm and the progress of the cold air by checking in at AccuWeather.com.
Travelers will want to make sure they and their vehicles are prepared for the snow and wintry temperatures.
A couple of days after the snowstorm affects the Midwest, another storm may bring snow to part of the East.
Which areas and how much snow falls will depend on the track and strength of the storm forecast to swing up from the Southern states later next week.
At this early stage, it appears snow is most likely to fall on parts of the southern and central Appalachians to a portion of New England.