I use an old pair of double layer nylon ski pants but my GTX PacLite rain pants would be about as breathable and lighter. Plus, if it's going to be very wet falling snow I'd go for the GTX pants to go with my GTX mountain parka and GTX/Thinsulate hunting boots.
Now if it's truly bitter cold (say 0 F. or lower) and windy I'd have my Cabela's GTX & Thinsulate ski pants W/ light poly long johns under. That's military Mickey Mouse boot, mittens and face mask weather.
BTW, As I get the money I want to convert to eVent clothing. The REI eVent parka will be high on that list. Very well thought out design.