Not completely

The general road closure was effective on 11/7 this year. However, Gardiner->Mammoth->Tower Junction->Silver Gate will remain open, though snow tires are often needed. This is basically the Lamar Valley area. You will be able to see large amount of hoofed animals, and good chance seeing wolf packs.

Friend of mine just came back from that general area. She said it's chilly and not easy to drive.