It isn't really a snow storm in the traditional sense. There is no need for a storm system, but rather just a major difference between the temp of water compared to the air temp. Add a slight breeze, and the effect is actually quite similar to snow guns on a ski hill.
http://en.wikipedia.org/wiki/Lake_effect_snow
If the weather stays cold (and it is forecast to do so for a few more days yet) this pattern can continue for a long, long time.