David Macfarlane of Park City was one of a group of five backcountry skiers from Utah skiing a steep north-facing slope on the north side of Anderson Mountain, immediately west of the Lost Trail Ski Area boundary and only a few hundred feet inside Montana, when he was caught and carried in an avalanche.
Avalanche danger generally rises when storms deliver significant snowfall to the mountains. The problems are manifold: Fresh powder can take a few days to bond to older snow it accumulates on, leading to storm-slab avalanches; light, unconsolidated dry powder can slough down steep slopes; and the weight of new snow can overload weak layers lower in the snowpack, leading to large avalanches of both new and old snow.