How much longer will Arctic air remain entrenched in Midwest, Northeast?
Temperatures well below average are expected to continue over the Midwest and northeastern United States through this week, with the worst of the cold forecast to settle into the Northeast on Wednesday.
A lobe of the polar vortex broke loose and spun southward over the weekend. Over the course of this week, this feature will spin from central Ontario to northern Quebec.
As the polar vortex spins across southeastern Canada, it will direct the flow of cold air across much of the eastern two-thirds of the nation into Wednesday.
Heating budgets, which have taken a hit in recent weeks, will be strained. The only consolation is likely to be a strengthening March sun that may provide some relief by day while driving a vehicle or standing near a sunny window.
Since the air has originated from the Arctic, it will regain its true identity at night, especially where skies are clear and there is snow on the ground. Low temperatures are forecast to range from below zero to the single digits and teens F from the northern Plains and Midwest to New England and the mid-Atlantic.
Motorists and pedestrians should keep in mind that areas made wet by melting snow during the day will quickly freeze toward sunset and remain icy, unless treated, into the morning rush hour.
While winds will continue to pale in comparison to that of a week ago, they will contribute to painful and even dangerous AccuWeather RealFeel® Temperatures over the next couple of days.
The North Central states, which have already experienced the harshest conditions from the outbreak, will remain very cold through Tuesday. Temperatures are forecast to slowly trend upward during the middle and latter part of the week.
For example, in Chicago, high temperatures will trend upward from the lower 20s on Tuesday to the upper 20s on Wednesday and Thursday to the upper 30s on Friday. The average high during this week is in the lower 40s.
As harsh as the cold has been in the Midwest, it pales in comparison to the extreme cold experienced in parts of Montana in recent weeks.
Temperatures in some areas of Montana for the entire month of February have been close to 30 degrees below normal. During the first few days of March, the temperature departures have been even more extreme.
On Sunday, Great Falls, Montana, had an average temperature departure of 50 degrees below normal with a high of minus 8 and a low of minus 32. The average high and low for the city are 42 and 19, respectively.
Elk Park, Montana, set a new all-time record for March in Montana on March 4 with a low of 46 below zero. The previous record in the state of minus 45 was set in Glasgow in 1897 and Fort Logan in 1906. The all-time record in the contiguous U.S. is minus 50 at Snake River, Wyoming, in 1906.
The Arctic air will continue to drill into the East.
Much of the Northeast can expect its coldest conditions on Wednesday.
In New York City, high temperatures will trend downward from the lower 30s on Tuesday to the upper 20s on Wednesday before bouncing back to near 45 on Saturday. The average high for Manhattan this week is in the middle to upper 40s.
The dry and cold air in the South will prevent thunderstorms from returning to much of the region, including tornado-ravaged areas of Alabama, Florida, Georgia and South Carolina through at least midweek.
However, there is concern for a severe weather outbreak that may first ignite farther to the west over the southern and central Plains to the middle Mississippi Valley as warmth builds this weekend.
In terms of ongoing cold weather, the polar blast finishing up this week should be the last widespread outbreak of frigid air for the season, according to AccuWeather Lead Long-Range Meteorologist Paul Pastelok.
"After this week, with a few brief exceptions, Arctic air will be locked up in northern Canada," Pastelok said. "There should be an increasing number of milder days as opposed to cold days for the middle and latter part of March in the Central and Eastern states."