don’t you need special permits for the winter?
Yes – you can’t just drive in like in the summer, which is a plus point! We didn’t just day trip in anyway – stayed at a Yellowstone Park lodge for a few days going out on ski trips round their waymarked trails, and then went to a Yurt camp with guided off-track XC ski trips. Transport in and out by snowmobile laid on by where we were staying – Yellowstone Park ones were ancient machines specifically built for the job, whilst the Yurt camp people used a converted 4×4.
It wasn’t cheap (cost more than going downhill skiing), but I’d definitely do it again given the chance!