Blizzard warnings are in effect for over 12 million Americans on Friday. Nearly 50 million people are under winter storm warnings. A blizzard is blowing or falling snow with winds of at least 35 mph for at least three hours. Falling and drifting snow can lead to whiteout conditions. Blizzard conditions occur most frequently in the central and northern Plains and Northeast.
Ground blizzards occur when already fallen snow is blown by howling winds. A winter storm watch is issued at least 24 hours before a blizzard is likely to occur. It signals that conditions are favorable for hazardous winter weather.