Lisa,

This question is not as straightforward as it seems. I have two authoritative references for you.

1. The water content of snow is more variable than most people realize. While many snows that fall at temperatures close to 32^oF and snows accompanied by strong winds do contain approximately one inch of water per ten inches of snowfall, the ratio is not generally accurate. Ten inches of fresh snow can contain as little as 0.10 inches of water up to 4 inches depending on crystal structure, wind speed, temperature, and other factors. The majority of U.S. snows fall with a water-to-snow ratio of between 0.04 and 0.10.
   http://nsidc.org/snow/faq.html
   
   
2. The algorithm generates 25 main diagnoses which correspond to a “mean” or “suggested” value for the snow/water ratio, associated with 6 snow categories: very heavy snow (R= 4:1), heavy snow (R= 7:1), ordinary snow (R= 10:1), light snow (R= 15:1), very light snow (R= 20:1), and ultra light snow (R= 25:1).
   http://meted.ucar.edu/norlat/snowdensity/from_mm_to_cm.pdf