Have you been to Yellowstone in the winter?

Have you decided on how you're going to get there? And where you're going to stay? Your chances of driving from Delaware to YNP without getting into a snow storm are pretty small. On one of my trips, I got to YNP in April. The roads were clear, but there was still a fair amount of snow on the ground. And it was COLD. Its all about altitude ASL. Here's specific weather information for Yellowstone over the last 107 years, by month. It snows in them thar' hills.
People visit in the winter, but most are locals that get around on snowmobiles. YNP is 8,000 feet above sea level. Even if you don't drive out, CGs aren't going to be open and flights into West Yellowstone airport are subject to weather restrictions. I think Old Faithful Lodge remains open all winter and Mammoth CG is open all year, but water freezes at 32 everywhere.
I'm not trying to talk you out of it. Only suggesting that you do your homework before the trip and then decide.

Great trip but really hard to get around. I would stay and tour a few days in West Yellowstone and then trek up to Bozeman and around the horn to the North Entrance and spend a few days there. The road from the North Entrance to the NE entrance is open year round and gives you great access to the Lamar valley which teems with animals all winter long (it is at a lower elevation than the rest of the park, meaning milder conditions for the ungulates and their lupine predators). For snowmobiling, West Yellowstone is better for the inexperienced rider, 100s of miles of groomed trails. The Northeast Entrance area (Cooke City - Silvergate)offers some of the best Alpine bowls and back country riding in the world, but it can be extremely dangerous for the inexperienced and unprepared. Several people die in avalanches each year. So it is imperative to know and respect your limitations. BTW, leave your RV home, this is an airplane and 4 wheel drive vehicle adventure

Years ago when my ex and I lived about 2 hours away in Idaho we went up and stayed in West Yellowstone. Rented snowmobile and rode it into old faithful. No tour. Amazing but a little chilly!

Was there years ago with several people from the company I worked for. We were there in early March, and was something to see. Stayed at West Yellowstone, took a day trip to Old Faithful. The wildlife by the river was awesome.
The snow was over the roofs of most of the buildings at Old Faithful, seeing it winter was far more interesting than seeing it in the summer. Overall a trip to remember for the rest of my life. Go, you won't regret it.

no I haven't. I don't even like to go outside to get the paper in the morning and I can't get the dog to do it for me either.

My sis and her hubby did it a few years ago. They had some sort of package deal (not a tour group) that included lodging, car rental, snowmobile self-guided tours, and tours on the Snowcat thing. They loved it, and had a blast.

The snowmobile company rented gear to them, and someone sent them a list of other recommended clothing. Things like a balaclava, layered outerwear, insulated boots, etc. That would be something to research before you go.

I'm going to stay home, keep warm, and watch the Yellowstone webcams.

We did our first winter visit in February of this year. It was amazing! We stayed two nights in the Mammoth Hot Springs Hotel, then took the snow coach to the Snow Lodge (Old Faithful) and stayed 3 nights there. We did a tour of the lower loop. We have worked 8 summers in the park and were blown away with our winter visit. If you want to go and stay in the park, call NOW for reservations. I made our reservations in August and our choices were somewhat limited. But, by all means, go!

We have been, but with a snowmobile guided trip and stayed in hotels. It is beautiful and not many visitors, and you can see lots of animals.

We went to West Yellowstone a couple years ago over Christmas. Were to take a Sno-Cat into park but there wasn't enough snow so went in tour van. great to see the bison and elk around the thermal areas. Many coyotes.
It was cold but sunny. Very warm in the rig.
Make sure where you are going is open. Reservations for some is necessary.