A blizzard is a severe snowstorm caused by strong continuous winds of at least 56 km/h (35 mph) and lasting for a prolonged period of time – typically three hours or more. A ground blizzard is a weather condition where snow is not falling but loose snow on the ground is lifted and blown by strong winds. Its Meteorological Terminal Air Report (METAR) code is BLSN. If the snow remains below 8 feet (2 m), it is called drifting snow (METAR code DRSN).
Blizzard conditions (source:NOAA)
Blizzards are severe winter storms that pack a combination of blowing snow and wind resulting in very low visibilities. While heavy snowfalls and severe cold often accompany blizzards, they are not required. Sometimes strong winds pick up snow that has already fallen, creating blizzard conditions.
Blizzards can create a variety of dangerous conditions. Snow and strong winds combine to produce a blinding snow - "whiteout" conditions (near zero visibility) and deep drifts due to the drifting snow. Blizzards also can cause a variety of other problems including runway contamination. Low friction indexes in combination with strong crosswinds can lead to hazardous conditions for takeoff or landing. Power outages can occur due to strong winds and heavy snow. Electrical transmission lines may be damaged, pipes can freeze and regular fuel sources may be cut off.
Accidents Caused by Blizzards
On 15 November 1987 a DC-9 operated by Continental Airlines from Stapleton International Airport in Denver, Colorado to Boise, Idaho crashed while taking off in a snowstorm due to a delay before take-off that led to upper wing surface contamination and a loss of control during rapid take-off rotation.
B732, vicinity Washington National DC USA, 1982 - On 13 January 1982, a Boeing 737-200 being operated by Air Florida on a scheduled domestic passenger flight from Washington National to Tampa FL failed to transition to a climb in day Visual Meteorological Conditions (VMC) after taking off from runway 36 and soon afterwards hit a bridge and vehicles on it before coming to rest in the Potomac River. The aircraft was destroyed by impact forces and 69 of the 74 occupants and 4 people on the ground were killed and 4 more on the ground were injured.