if your rear fender is as pictured, it's going to collect snow and cause quite a lot of rolling resistance, especially with knobby tires.
if possible, I'd trade your pictured knobbies, which I think is designed for gravel, for some mud specific ones. Mud and snow tires are quite similar, except the snow tires have studs in them.
Last edited by AEO; 11-20-11 at 08:49 PM.