Thanks for the advice!

Zermatt and Chamonix may be a bit far to go out and back in one day. We weren't planning on renting a car. I don't know that I would be comfortable on unfamiliar mountain roads in the winter. And if the weather is bad, it's a long way to go for no scenery...

Maybe the thing to do is a train to Lausanne or Bern (or both, time permitting).

I'd like to plan a later trip to see some of the mountains. The Jungfrau trip looks amazing.