Airlines have canceled more than 13,000 U.S. flights for Saturday and Sunday as a massive winter storm is forecast to bring a mix of ice, snow and frigid conditions to many parts of the country this weekend.

Heavy snow, sleet and freezing rain are expected across large parts of the U.S. as the dangerously cold weather causes major power outages and travel disruptions.

Utility companies braced for power outages because ice-coated trees and power lines can keep falling long after a storm has passed.