If it's in your affordability, I highly recommend a Surly Karate Monkey. You can put any size of 29" or 700c tires on it because they are the same rim diameter, plus you can mount disc brakes. Remember, taller tires are ALWAYS better in snow, and disc brakes are ALWAYS better in snow. If you buy a steel framed bike new, make sure to have the insides of the tubing treated with Frame Saver or lindseed oil before you start riding it.