Hey,
So I have not personally tried this but it's worth looking into. I seen someone use this technique but for grass rather than snow. Anyways it's quite easy, what he did was take a ton of sawdust put in a bowl and mixed with cheap accrylic paint with a little water. Obviously you are going to use white paint rather than green paint but it's the same concept.
Any ways here is the link
http://youtu.be/zPHg5T82OuM
Hope this helps good luck and cheers!