This infamous weather pattern is actually partially influencing our weather as February winds down. And it’s likely to happen again during March.
What is a polar vortex? How it affects snow and ice in the United States
A polar vortex is a large region of cold air that circulates over the North Pole. If the wind is strong, the wind will be suppressed, but if the wind weakens, it may sway or stretch.
Hello, is it spring?
Weather forecasts are promising warmer weather as the calendar turns to March. Dramatic warming is expected in the East, with the Climate Prediction Center’s outlook for March 6-12 showing warmth spreading across much of the country, including the troubled Northeast.
But the winter weather boogeyman may still be lurking.
“The effects of the polar vortex are far from over,” AccuWeather meteorologist Paul Pastelok said in an email to USA TODAY.
This infamous weather pattern is actually partially influencing our weather as February winds down. And it could rain again throughout March, forecasters told USA TODAY.
Sunday, March 1st, on the other hand, is the meteorological first day of spring, and meteorologists expect the weather to become more spring-like over the next three months (though it may take a few weeks for the calendar to catch up).
Polar vortex contributed to the formation of multiple cold wave outbreaks
The polar vortex was the biggest news story this winter in late January and early February, as it was a key factor in the arctic air flowing into the eastern United States from the south, helping to produce record cold and memorable snowstorms.
As meteorologists predicted multiple cold snaps this winter, the polar vortex was often one of many forces at play. After the dust settled, experts found just one example (in late January to early February) where sudden stratospheric warming (and the resulting disruption of the polar vortex) was the primary cause of subzero weather in the United States.
But another phenomenon, the disruption of the Arctic Oscillation, also contributed to the frigid temperatures.
Experts, including NOAA Climate Prediction Center meteorologist Laura Schiast, tend to describe cold wave outbreaks as a dance between multiple weather forces.
“It’s been an active winter for both the stratospheric polar vortex and the Arctic Oscillation (AO),” Siasto told USA TODAY via email.
The polar vortex has become a popular topic in winter weather, in part because of its catchy name. But meteorologists say this is a complex and confusing climate-changing force that operates in mysterious ways.
First, a weak polar vortex tends to send cold air into the United States because it cannot be contained above the North Pole. (Another explanation: Meteorologists distinguish between stratospheric and tropospheric polar vortices based on where the cold air is located in the atmosphere.)
Changes in the polar vortex could once again shape March forecasts
Pastelok said the polar vortex is not the only weather system at play, but a “prong” of the vortex extends across eastern North America, impacting cold, snow and ice across the Great Lakes, Northeast and mid-Atlantic into early March.
Polar vortex expert Judah Cohen of MIT told USA TODAY that “another sudden stratospheric warming seems almost inevitable, this time leading to a splitting of the polar vortex. This looks like it will happen at the end of the first week of March.”
(Sudden stratospheric warming is the rapid warming of the skies above the North Pole that disrupts the polar vortex, which could set the stage for major winter weather changes here in the U.S. in the coming weeks.)
Cohen said the warmth could be replaced by more cold weather later in the month. “We expect a period of calm in the eastern United States to continue until near the spring equinox,” Cohen said. “Then I think we’ll end up with cold weather in the eastern U.S. related to the polar vortex breakup in late March or early April. That could last for a while.”
Pastelok noted that we still need to be careful about the path of the storm in late March. “We’ll probably see some late winter storms somewhere from the upper Midwest to the interior Northeast.”
Cold waves may affect the West this time
This time, Pastelok said the effects of the breakup vortex will extend to cold and stormy weather across western North America in early March. Conversely, many parts of the eastern United States will experience warmer-than-normal temperatures from March 5th to March 15th. “This could lead to rapid snowmelt and ice jams, leading to flooding from the Ohio Valley to the Northeast.”
Cohen agreed with Pastelok, saying, “Ironically, while everyone is most excited about the splitting of the polar vortex (which will make winter weather even more severe), I think the only guarantee is that it will likely bring a multi-week period of calm to the eastern United States. If anything, it will probably favor colder, stormier weather in the western United States.”
Doyle Rice is a national correspondent for USA TODAY, specializing in weather and climate.
