Snow and wind will combine to create dangerous avalanche conditions as a winter storm arrives today. Slab avalanches 1-3' thick could release without a human trigger and from a distance. Be particularly careful near or below areas where wind is building drifts. A weak layer of snow increases the chances that you could trigger and avalanche from a great distance or on a slope above you.
A buried weak layer of facets resulted in widespread avalanche activity in the northern portion of the Greys River zone. Expect more avalanches on this layer today as wind and snowfall overload the layer.
New snow and strong winds will build increasingly large drifts of snow today. Southwest winds approaching and possibly exceeding 50 mph will build firm slabs even below ridgetops. These slabs will further strain the existing weak layers.
There is a complex, early season snowpack in avalanche terrain currently. Facet and crust combinations with a very weak structure exist above 8,000' though have generally lacked a significant slab or load on top. Until two days ago, no significant avalanche activity occured on these layers beyond some thin wind slabs. That situation is changing. Two days ago, a 2-3' thick slab released with explosives on the drought layer at Targhee on a southeast aspect, and yesterday, widespread avalanche activity was reported in the Squaw Creek area (northern Greys) on northerly aspects. The missing ingredient for widespread and/or large avalanches has been a slab on top of this weak snow. Today's new snow and wind will change that situation. These weak snow layers will be tested throughout our forecast zones, especially tonight and tomorrow.
