I will be finishing a Christmas market cruise in Regensburg on Dec. 1 and have a few days before flying out of Munich. I love Christmas markets! I have been to Rothenberg ober Taber, Salzburg, Frankfurt and don’t need to return. I am interested in the Alps but know the weather could be bad. Thinking of Augsburg, what else?
I lived in Augsburg for four years and loved it. Suggest spending a day there. They have a Christmas Market there in front of the Rathaus.
Also, you could do a couple of days in Garmisch, go up to the top of the Zugspitze. You will see many people skiing.
Unless you want to spend most of your 3 days traveling I'd pick either Nuremberg or Ingolstadt. Nuremberg is more famous, but it will be very crowded for the Kristkindlemarkt at that time of year. Still, it's a great place to visit and easy to get to Munich from. Ingolstadt won't be as crowded, but it's nice and has a decent Christmas market, and it's a straight shot from there to Munich also. Or you could just go straight to Munich and do the markets there.
Hope you plan to spend a couple days in Regensburg. It is a beautiful, interesting city with two Christmas Markets. Regensburg is our favor city in Advent Season.
We are in Augsburg as I write this. I have not visited its Advent Market since the 1970's but the town is well worth a couple days.