Knowing the extent of snow cover across Canada and the lower 48 states is important for predicting winter weather. Among other things, this graphic helps meteorologists determine daily temperatures and future storm tracks. An expansive snow pack enhances the likelihood of cold air masses sinking southward from Canada and thwarts warm air trying to surge northward. This can directly impact the track of storm systems, as often times low pressure areas traverse the southern periphery of a cold air mass.