atmospheric storm ground blizzard envoAtmo This form of blizzard does not involve snowfall as the snow which is blown by the winds is already present on the ground. To qualify a snowstorm as a blizzard, some sources require the windspeed to be at least 56 km/h and the duration of the storm to be at least three hours. We set no such hard boundaries in this definition, as this should be done with reference to local standards. environmental_hazards A ground blizzard is a storm during which snow which has settled on a planetary surface is resuspended in and transported through its atmosphere by strong winds, sustained for several hours.