What is a long severe snowstorm called?

Blizzards are dangerous winter storms that are a combination of blowing snow and wind resulting in very low visibilities. Officially, the National Weather Service defines a blizzard as a storm which contains large amounts of snow OR blowing snow, with winds in excess of 35 mph and visibilities of less than 1/4 mile for an extended period of time (at least 3 hours). In the 1870s, an Iowa newspaper used the word "blizzard" to describe a snowstorm. Previously, the term blizzard referred to a canon shot or a volley of musket fire. By the 1880s, the use of the word blizzard was used by many across the United States and in England.

Source: National Weather Service