1.   An unusually deep snow cover since November has encouraged many frigid nights.

2.   Ample snow cover in much of the northern Plains is helping contribute to lingering chill.

3.   An unusually widespread, deep early season snow cover in the Dakotas and Minnesota has led to many record minimums as well as frigid daytime readings.

4.   As a result, snow cover is exceptionally deep across the northern parts of New England and New York.

5.   As warm air moves over the fresh snow cover in the Northeast, fog and drizzle will form, especially across the interior valleys.

6.   At night, snow cover allows energy to radiate to space more efficiently than bare ground.

7.   At night, snow cover radiates energy to space more efficiently than bare ground.

8.   Avalanches usually form when either a cornice of snow breaks loose from the edge of a mountain or a slab of snow slides off an existing snow cover.

9.   Both the lack of snow cover and a nearby moisture source also enhances the warming of west winds on the high plains.

10.   A deep snow cover helped chill the surface air.