First I would worry about snow/ice being packed onto your tire, especially the inside. Next, alignment. Do you have to fight with the car to keep it straight? Go on the highway, and drive on a straight section...let go of the wheel for a few seconds, and if the car drifts like crazy to one side, then your alignment is probably out. (your car should slowly drift to the right, but basically should stay straight for a while) Watch out for the potholes, though! /images/graemlins/rolleyes.gif If it isn't one of these, I would go and get your wheels balanced. These are all fairly cheap tests/experiments, so I would start with these. If none of these fix your problems, then you might have bigger issues.
If you need a really good place for alignments/wheel balancing, send me a PM. Great place for alignments, and they balance the wheels while they are on the car...more accurate than normal balancing.