Why does fronts occur at blizzards?

The question would be better phrased as why do blizzards occur at fronts. A weather front is a natural phenomenon and often occurs where air masses differ in moisture and temperature. A storm front with rain has warmer temps at higher elevations than a storm front with hail. A storm front at cold temperatures can bring dry snow, wet snow, sleet (icy rain), ice, or a blizzard-- and what occurs depends on the moisture and temperature. A blizzard may arise where two fronts merge, collide, or interact, and how fast the fronts "move". A fast moving front dumps less rain or snow than a front that is slow-moving or stalled.