What is a 'polar vortex' and why is it so dangerous?

A spiraling pool of cold, dense, arctic air called a "polar vortex" began its frigid sweep of the U.S. today. "It's just a dangerous cold," said National Weather Service meteorologist Butch Dye this morning. The arctic chill is 

As the coldest air in 20 years surges into major population centers in United States, many are raising eyebrows over its rare cause: the positioning of the polar vortex. A polar vortex is a large pocket of very cold air, typically the coldest air in

Threatening not just records but lives, a blast of arctic air packing the lowest temperatures in two decades descended on the Midwest on Monday and began a brutal plunge across most of the United States. People in 

A spiraling pool of cold, dense, arctic air called a "polar vortex" began its frigid sweep of the U.S. today. "It's just a dangerous cold," said National Weather Service meteorologist Butch Dye this morning. The arctic chill is 

A so-called "polar vortex" of dense, frigid air descended upon much of the U.S. Monday, dropping temperatures in some parts of the country to near-record lows and prompting wind chill warnings from Montana to Alabama. The Midwest is being hit with the