Bridger Range

The recipe for Persistent Slab avalanches only exists on higher elevation and shadier slopes. Without recent loading they have become harder to trigger. Dig down to look for weak layers near the ground before committing to steep slopes. Be on alert for Wet Loose avalanches if you find a wet, unsupportable snowpack.

There are two very different sorts of avalanche concerns today: Persistent Slab avalanches and Wet Loose avalanches. 

Persistent Slab avalanches will break on the weak, old snow at the base of the snowpack on higher elevation and shadier slopes. 

Multiple large, fresh avalanches were reported around Cooke City yesterday (observation). Yesterday’s avalanche warning has expired, but avalanche conditions remain quite dangerous. You could easily trigger big slides from flat terrain below steep slopes (Daisy Pass avalanche). Persistent Slab avalanches have been taking out the whole snowpack, breaking up to 5 ft deep, down to the ground. Continue to give steep slopes a wide berth today and wait for the weak layers to adjust to the big load they’ve just received. Avalanche danger is CONSIDERABLE at all elevations near Cooke City.

Yesterday, Ski Patrols in the northern Madison Range triggered many large Persistent Slab avalanches with (relatively small) explosives, some breaking unusually wide. This clearly indicates that the snowpack remains unstable. Big, human-triggered avalanches remain likely today on slopes with weak, old snow near the ground in the N. Madison and N. Gallatin Ranges and the avalanche danger is CONSIDERABLE in these areas.

In the Bridger Range, S. Madison Range, S. Gallatin Range, and Lionhead and Island Park areas, the recipe for Persistent Slab avalanches is less widespread and without recent loading they will be harder to trigger. Dig down to look for weak layers near the ground before committing to steep slopes. The avalanche danger is MODERATE in these areas.

Wet Loose avalanches are an unusual avalanche problem in mid-December, but the weather has been usual. Really warm temperatures and rain yesterday in the mountains around Bozeman and Big Sky has added this concern in those areas. I don’t expect these slides to be big - there just isn’t that much snow at the low elevations where the snowpack is the wettest. Still, be on alert if you’re finding a wet, unsupportable snowpack, particularly in places where a small slide would have big consequences (e.g. above rocks, cliffs, or gullies).