What Is A Blizzard?

BOSTON -- Although they don't seem to get the same kind of attention as hurricanes, and Hollywood hasn't made movies about blizzards the way it has about tornadoes, these powerful winter storms can be every bit as dangerous and damaging as those seemingly more common weather phenomena.

What exactly is a blizzard? National meteorologists have specific criteria for these winter storms, which are characterized primarily by high winds, low temperatures, and enough blowing snow that visibility is seriously reduced for a significant period of time -- more than three hours.

Temperatures are usually below 20 degrees and winds above 35 mph for a storm to be classified as a blizzard, especially where visibility is under one-fourth of a mile. A severe blizzard would have temperatures lower than 10 degrees, winds above 45 mph and zero visibility.

Blizzards often develop on the northwest side of a storm system, with differences in low and high pressure systems creating strong, high winds.

The combination of snow, sleet, ice and heavy winds can cause power outages, traffic accidents and backups, and other public safety problems.

Such was the case in the Blizzard of 1978, from Feb. 5 to Feb. 7, a weak area of low pressure moved across the Great Lakes, weakening even further. Another low formed off the mid-Atlantic states, intensified and drifted north.

It stalled over southern New England for 24 hours, dumping up to 3 feet of snow in some areas, from the upper Chesapeake Bay area to the northern New Hampshire mountains. More than 23 inches fell in the Boston area in 24 hours.