First obstacle going east will be getting over the Sierras before snow closes the roads. Don't know the odds, but they'll be worse in December (going west) than October (going east). Lather, rinse, and repeat for every pass until you get to central Colorado.
I'd prefer the occasional snowfall in the Appalchians that can close your route (to a bicyclist, with common sense but no chains) for 3-4 days around the end of the year to being holed up in a mountain camp in Utah until the spring thaws.
Note, too, that you'll be down to 9-10 hours of sunlight, while summer tourists can expect 14-15 hours.