Travelling in the winter is a whole other animal. For those that have done it before, you know what I'm talking about but if this is your first time, first of all, you'll be glad you came across this article, and two, unless you're well-prepared, travelling below freezing is not fun at all.
Geeking out for a moment, when you fall into the rabbit hole of technical outdoor gear, the concept of the 3 layer system comes up a lot. For a true below freezing winter packing list, I think a 4 layer system works the best
This cold weather packing list isn't meant to be definitive but it will give you guidance on what you should pack, identify gaps in the gear you already have, what you may not have thought of, and what you should leave at home.
The best tip is to not overpack. Go with the expectation that you will wear your core set of layers everyday since you won't sweat that much so you don't necessarily need that many copies of the same thing except underwear of course.
Are there tips for packing light for winter travel?