AccuWeather long-range experts say a major shift in the weather pattern could bring frigid air to parts of the United States starting during the second half of March, with impacts that could potentially last into early April in some places.
“Don’t put your winter jacket and gloves away just yet. Winter is far from over,” said AccuWeather Lead Long-Range Expert Paul Pastelok. “Many parts of the central and eastern U.S. will see a surge of springlike warmth next week, but the polar vortex could contribute to a sharp drop in temperatures across parts of the U.S. during the week of March 17.”
The polar vortex is a part of Earth’s atmosphere that is found over the North Pole. Strong winds typically keep the vortex locked in place, but periodically, changes in the weather can cause the vortex to wobble and even separate into pieces, which results in waves of frigid Arctic air being ushered southward across North America, Europe and Asia.
Not every cold snap is connected to the polar vortex, but when it does weaken, it can result in some of the lowest temperatures of the winter season in North America.
“The polar vortex has been rather strong all winter. There have been a few instances where it has been stretched and not circular over the North Pole,” Pastelok explained. “Most cold spells in the U.S. this winter were not connected to the polar vortex.”
A “sudden stratospheric warming event” into next week will weaken the winds that confine the polar vortex to around the North Pole. As a result, it is expected to shift away from its polar residency, eventually sending cold air from the Arctic into North America and Eurasia.
When the stratosphere warms suddenly over the North Pole, it weakens the polar vortex and causes the normally pent-up frigid air to be displaced southward over one or more continents of the Northern Hemisphere. Following a sudden stratospheric warming event, lobes of the polar vortex may also shift southward with the jet stream which can enhance the impact of the frigid air by adding strong winds.
AccuWeather Lead Long-Range Expert Paul Pastelok said the shifting and stretching of the polar vortex could impact the U.S. around the middle of March, with impacts potentially lingering into early April.
Last autumn, AccuWeather long-range experts predicted the transition from winter to spring as the period most likely to experience the polar vortex allowing colder air into the U.S.
With plenty of cold air in place, the colder pattern during the second half of March could set the stage for springtime snowstorms. Pastelok said there are signs that a major storm could unfold across the central and eastern U.S. around St. Patrick’s Day weekend.
“This could be the beginning of a rough and stormy pattern for eastern North America through the rest of March into early April,” Pastelok said.
A prolonged period of colder weather could result in higher heating and electric bills, on the heels of a winter that was colder and snowier than others in recent years.
Pastelok also said that the upcoming pattern could limit the severe weather potential from the Upper Midwest, Great Lakes, and Ohio Valley on east through the end of the month.
