ok i was there in late february last year, and we had a huge snowstorm over night fresh pow you know, just perfect conditions. At the summit it was fucking cold but when i got down to this valley, they had a thermometer by a chairlift and i swear to god it was 65 degrees.
basically, the weather in montanna is really crazy. I have the burton poacher outfit, and all i wore under neath was the warm underarmour and a northface fleece sometimes. Just layer well, and youll be fine. You dont really need like a whole gore tex suit but i do recomend gore tex gloves. I had em and they were really nice