NEW YORK (AP) — An arctic outburst has brought extreme cold, heavy snow and intense winds to much of the United States — just in time for the holidays.
The weather system, dubbed a “bomb cyclone,” is disrupt travel and causing dangerous winter conditions. Where does this wintry weather come from and what does the coming days have in store for us?
WHAT IS HAPPENING?
A cold air front descends from the Arctic, sending plunging temperatures.
Much of the United States will experience below-average temperatures, said Bob Oravec, chief forecaster for the National Weather Service in College Park, Maryland.
Temperatures can drop more than 20 degrees Fahrenheit (11 degrees Celsius) in just a few hours, the National Weather Service predicts.
Wind chill temperatures could drop to dangerous levels well below freezing, enough to cause frostbite within minutes. In parts of the Plains, wind chill could drop to minus 70 degrees Fahrenheit (minus 57 degrees Celsius).
According to the National Weather Service, those in the Plains, Upper Midwest and Great Lakes were cautious and expected blizzard conditions as high winds kicked up snow.
WHO WILL BE AFFECTED?
Almost everyone east of the Rockies — about two-thirds of the country — will see extreme weather, said Ryan Maue, a private meteorologist in the Atlanta area.
Although much of the west coast is sheltered from the cold, the arctic front is expected to pass east and south all the way through Florida.
Heavy snowfall and intense winds could be bad news for air travel, Oravec said.
And for those planning to hit the road for vacation, “you’re going to have some pretty severe whiteout conditions,” Maue warned.
HOW LONG WILL IT LAST?
This weather system is expected to bring a major “weather boost,” said Judah Cohen, a winter storm expert for Atmospheric Environmental Research.
The cold won’t last long. After the dramatic drop that will keep temperatures low for about a week, “everything will return to normal,” Cohen said.
Shortly after Christmas, temperatures are expected to start to warm again, moving from west to east. They are expected to remain near normal through the end of the year in most of the United States
WHY DOES THIS HAPPEN?
It all started further north, as frigid air piled on the snowy Arctic floor, Maue said.
Then the jet stream – flickering air currents in the middle and upper parts of the atmosphere – began to push this cold pool toward the United States.
As this arctic air is pushed into the warmer, wetter air ahead of it, the system can quickly turn into severe weather – including what is known as a “bomb cyclone”, a rapidly developing storm in which the atmospheric pressure drops very rapidly in 24 hours.
These severe weather events typically form over bodies of water, which have plenty of heat and humidity to fuel the storm, Maue said. But with the massive amount of cold air passing through, we could see a rare cyclone bomb forming over the land.
IS THIS NORMAL?
The storm is certainly strong, but “not unheard of for winter seasons,” Oravec said.
It is quite normal to have cold air in the winter. This week, however, changes in the jet stream pushed air further southeast than usual, Oravec said – sweeping frost across the country and making storm conditions more intense.
The United States is unlikely to hit record lows, like those seen in the 1983 cold spell or the 2014 polar vortex, Maue said.
Still, “for most people alive, this will be a memorable event among the 10 coldest extremes,” Maue said.
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The Associated Press Health and Science Department is supported by the Howard Hughes Medical Institute Science and Education Media Group. The AP is solely responsible for all content.
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