snow cover . (a) All snow that has accumulated on the ground, including that derived from snowfall, drifting or blowing snow, avalanches, frozen or unfrozen rain stored in the snow, rime, and frost. (b) The areal extent of ground partly or wholly covered with snow in a particular area, usually expressed as a percent of the total area. (c) The average depth of accumulated deposited snow on the ground in a particular area, usually expressed in centimeters.