Have you noticed that the snow cover appears to be going away slowly?
Notwithstanding the tireless efforts of the Public Works department to remove enormous quantities from our streets it is going away elsewhere as well. Perhaps too slowly for some of us, but despite the fact that the temperature has remained at or below the freezing point (with the exception of this past weekend) the piles are smaller and a few patches of bare ground are making an appearance.
But where are the runoff puddles from this melted snow? Given the large amount of moisture that is trapped in that snow bank, we might expect to see rivers of meltwater cascading off but that is not generally the case. For the answer we need to recall high school chemistry class and the fact that not all solid matter has to melt into a liquid phase in order to achieve a gaseous or vapor stage. Sometimes the shortcut happens and the solid moves to a gas directly — the term is sublimation. An example of another substance which will sublime is the ubiquitous moth ball. When you place some moth balls in the closet and check on them a year later they will be smaller, but you will notice the aroma — they have missed the liquid phase and changed directly to a gas.
So it goes for our snow — the air above the snow is dry, and the frozen moisture changes directly into water vapor even if the temperature is below freezing. Some settling will occur as well, shrinking the depth of the snow, and the overall picture provides more hope for the arrival of Spring.