Upvote:2
Skip it this time
Unless you are interested in skiing, there are limited activities, and you will miss a lot.
All the major national parks (Rocky Mountain NP, Yellowstone, Grand Teton, Glacier etc) will be closed or partly closed. As will many hotels, most scenic roads/passes and so on. You can look for individual information about each park and its surroundings here.
The majority of this infrastructure will be closed until April (or later).
However, you can try to visit some alternative destinations, like Las Vegas, Grand Canyon, and some of Utah's national parks (which will be open), like Zion or Arches.