Why more frequent cold blasts could be coming from global warming

Frigid air that normally stays trapped in the Arctic has escaped, plunging deep into the United States for an extended visit that is expected to provoke teeth-chattering but not be record-shattering.

It’s a cold air outbreak that some experts say is happening more frequently, and paradoxically, because of a warming world. Such cold air blasts have become known as the polar vortex. It’s a long-established weather term that’s become mainstream as its technical meaning changed a bit on the way.

What it really means to average Americans in areas where the cold air comes: brrrrr.

What’s happening is the jet stream — that usually west-to-east river of air way above ground that moves weather systems along — has made a roller-coaster like dip from the Pacific Northwest to the Southeast and is stuck on that wavy track. To the west of that plunge, in California, it’s hot and dry. But to the east and just above the dip, it’s a taste of the North Pole.

“We’re just getting a lot of cold Canadian and Arctic air that’s being just channeled from north to south,” said Dan DePodwin, AccuWeather director of forecast operations. “We really expect this to be more of a prolonged stretch of well below historical average temperatures. We’re talking 12 to 25 degrees Fahrenheit (7 to 14 degrees Celsius) across a large portion of the eastern half of the country.”

The worst will be in areas that just got hit with heavy snow, from Kansas to Washington, said National Weather Service Weather Prediction Center meteorologist Zack Taylor: “That’s where we could see actual overnight lows down well into the single digits, perhaps even below zero in some places across the Ohio Valley and the Plains.”

Judah Cohen, seasonal forecast director at the private firm