Ground blizzard

Ground blizzard refers to a weather condition where loose snow or ice on the ground is lifted and blown by strong winds. This can occur in the absence of precipitation, and can even occur when the sky is clear. This is in contrast to "ordinary" blizzards, which are accompanied by heavy falling snow. They can be especially dangerous as they occur after a winter storm has passed, when it is assumed that all forms of severe winter weather has ended.

Meteorological criteria

While the term "ground blizzard" is often associated with intense blowing and drifting snow conditions, there are specific criteria which must be met. Often such criteria will be determined by a country's governing weather agency or other similar body. In the U.S, according to the National Weather Service a blizzard is defined as having sustained winds or frequent gusts of 35 mph or more, visibility frequently below 1/4 mile in considerable snow and/or blowing snow, and the above conditions are expected to prevail for 3 hours or longer. Environment Canada similarly maintains that widespread reduction of visibility to less than 400 meters due to snow and/or blowing snow and sustained wind speeds or gusts of 40 km/h or more must be present for at least 4 hours (6 hours for the Northwest Territories and Nunavut)

Types

There are three different forms of ground blizzards:

In horizontal advection conditions, the winds blow across the surface of the earth with very little if any large-scale upward motion.

In vertical advection conditions, the winds exhibit large-scale upward motion lifting the snow into the atmosphere creating drifting waves of snow up to 500 meters in height.

In thermal-mechanical mixing conditions, massive convective rolls form in the atmosphere and the blizzard may be observed from space with the blizzards convective rolls creating waves of snow (also known as snow billows) resembling lake or ocean effect snow bands.