Wall mart and zellers here sell cheap nylon running pant shells. these work pretty
good for shedding dry snow and wind.

I generaly wear one of two bottom layers in winter.

both start with a pair of polyproylene long underwear (I wear NO cotton).

Then for option 1 I add a pair of fleece pants - usually 200 weight, and top with a rainpant or nylon shell pant - these can be found cheap at walmart usualy.

For option 2, I Might wear a light nylon shell pant over the longjohns, and then step into
a pair of surplus british navy wool arctic watch pants. heavy, huge and totally warm, with
a pair of suspenders on them. Often in these I dispense with the nylon shell pants inside.