Blizzard: what is it?

The term blizzard first designates a storm ofwinter, powerful and prolonged (more than 3 hours, but less than 3 days in principle) during which the temperatures are largely negative (down to -50 ° C) and strong winds snowy (up to 150 km.h^-1) drastically reduce visibility (less than 1 kilometer) on the ground.

Note that usage also wants the term to be used to qualify storms of snow that occur in windy weather in the polar regions.

A surface blizzard can form on relatively flat terrain, when powdery snow has accumulated on the ground and the wind makes it dance. This happens when a strong anticyclone arrives behind a depression, in Siberia or northern China, for example.

The dangers of a blizzard

A blizzard is formed in particular when a low pressure is heading towards a high pressure area and, in fact, the gradient of atmospheric pressure between the two systems is reduced. The winds then lift the falling snow. This blizzard is referred to as a storm blizzard. He is particularly well known to Canadians – and to Montrealers especially – and to residents of the Northeastern United States. In 1916, the blizzard in Montana dropped the temperature from 7 ° C to -49 ° C in just 24 hours.

In blizzard weather, you are strongly advised not to leave your home. In fact, the low visibility that reigns during such a phenomenon – sometimes not much more than a few meters – increases the risk of getting lost and suffering a hypothermia which can prove fatal, given the difficult circumstances and extremely low temperatures.