What Is the Polar Vortex Sending an Arctic Blast Into the US?

A winter storm descending on the US is expected to deliver heavy snow and ice to more than 150 million people across roughly two dozen states. Forecasts predict the storm will plunge Texas into a deep freeze before moving eastward and hitting major Northeast cities such as New York City and Boston.

The storm is being driven by a potent weather phenomenon: a disruption of the polar vortex.