Andrea Strohak, age 9, of Niagara Falls, Ontario, Canada, for her question:
WHAT CAUSES A BLIZZARD?
Blizzards have been known to pile up tremendous snowdrifts within a short period of time, and it isn’t uncommon for the deep snow in the path of the storm to completely disrupt daily life for many days. It becomes almost impossible for most forms of transportation to move, and as a result all businesses and schools are often forced to close until there is a cleanup.
Blizzards most frequently happen in central and eastern Canada and in the northern Great Plains section of the United States. They’re also common in various parts of northern Russia.
A blizzard is a blinding snowstorm that features tremendously strong and very cold winds. It is caused by an extremely cold air mass moving out of the Arctic into the Temperate Zone.
As cold, heavy air moves down from the north, it forces the warmer, moist air to rise along the boundary between the two air masses. This boundary, often stretching for many miles, is called a cold front. The rising action of the air produces a heavy snowstorm and powerful, very cold winds.
Quite often the most severe blizzards occur following a period when there is usually warm winter weather.
A blizzard is defined by the National Weather Service of the United States as a snowstorm with winds of 35 miles per hour or more. To meet the definition, the winds must have temperatures of 10 degrees F. It becomes a “severe blizzard” when the winds are 45 miles per hour or more and the temperatures are less than 10 degrees F.
During a blizzard, visibility is less than 500 feet, while during a severe blizzard, visibility drops to zero.
To be classified as a blizzard, the storm must have the required marks of intensity. Otherwise the rating is simply “storm.”
A storm can also be marked by strong winds and snow, but often it involves rain or hail. We would never have storms if the temperature of the air were the same everywhere. It’s when air in the low latitudes becomes heated and meets the cooled air from the northern latitudes that violent action can be expected.
It is part of nature’s winter plan for the large masses of cold air from the high latitudes to spread out toward the equator. Eventually the large masses break into separate, smaller masses and they generally move eastward and southward. In the middle latitudes these wandering masses of cold air meet the warm air masses that have come up from the low latitudes at nature’s command. Differences in temperature, pressure and humidity mean that a weather struggle will result, and chances are good we’ll have a storm or a blizzard.