Significant winter weather for a watch means 5 or more inches of snow and/or sleet within 12 hours, or 7 inches of snow/sleet within 24 hours, or ice accumulation that could cause damage to trees and powerlines, or life-threatening combinations of snow and/or ice with wind.

Heavy snow was falling over Northwest Texas and Oklahoma City on Friday morning (January 23) as a major winter storm began moving east across the U.S., bringing deadly cold and the threat of power outages and treacherously icy roads to almost half the nation's population and prompting more than a dozen governors to declare states of emergency.

Winter Storm Fern was forecast to spread heavy snow, sleet and dangerous ice to tens of millions of Americans across two dozen states beginning on Friday, Jan. 23, and continuing into the weekend.