I'm planning to take a week long trip to Breckenridge, Colorado in the second week of January in my '14 Forester and wanted to know how the driving is all the way there. I've driven there in the Spring, but never done it during the winter with all the ice. Is there anything I should keep in mind? Is it mandatory that I purchase new winter-only tires and exchange the factory all-season tires? Any help/suggestions is much appreciated!