I hunt in snow from October to April, in temp's from +5c to -25c (don't take hounds out below that)so I can maybe add little to this subject.....
The type of snow, and the tempriture of the air will determin what kind of scenting you will find.
A hound that is used to hunting on snow will fly on grass, but if a hound isn't used to the white stuff, I think he will struggle just because of the drastic change in conditions.
The closer to 0c and the wetter the snow the better the hunting. imo