Cooke City

10” of low density snow fell with light winds. Keep on the lookout for signs of wind loading and back off steep slopes if you find them to avoid triggering a Wind Slab avalanche. Dig to investigate weak layers before committing to steep slopes held onto old snow.

New snow and wind are driving the avalanche concerns today. 

The Bridger Range, northern Gallatin Range, and northern Madison Ranges got the most new snow (5-11” depending on the range and elevation) and westerly winds have been blowing hard enough to transport that snow into thicker, deeper, and more cohesive slabs. Wind Slab avalanches large enough to bury you will be easy to trigger on wind-loaded slopes. You might also be able to trigger thin Storm Slab avalanches or Loose Dry sluffs on non-windloaded slopes, but I don’t expect these to be large enough to cause much of an issue. A skier out in the Bridgers during the storm last night reported small avalanches in the new snow, cracking, and unstable test results - all signs that the new snow is unstable (observation). The depth of new snow seems to have increased dramatically with elevation, so watch out for more dangerous conditions as you ascend. The avalanche danger is CONSIDERABLE in these ranges.

Cooke City got 10” of new snow, but that snow was lower density and winds have not been as strong, so the Wind Slab problem will be less widespread. Still, be on the lookout for this problem, and if you encounter signs of it (such as a noticeable stiffening of the snow under your feet or sled, or cracks shooting out in front of you), stop and retreat to lower angled slopes. There is a MODERATE avalanche danger at all elevations in the Cooke City area.

There is less new snow in the mountains near West Yellowstone and Island Park. Wind Slabs avalanches are still the primary concern, but the wind drifts will be smaller and only an issue at higher elevations where snow depths are a little deeper. The avalanche danger is MODERATE at mid and upper elevations in these areas.

Wind-sheltered slopes will hold the best quality, and safest, riding conditions. Watch for rocks and stumps that have hidden by this new snow. 

Across the advisory area, Persistent Slab avalanches are an additional concern on slopes that harbor snow that fell prior to Thanksgiving (mostly above roughly 8500 ft). We’ve had a number of reports of cracking and collapsing on weak snow at the bottom of the snowpack at these higher elevations (observation, observation, observation). We haven’t heard of any slides breaking on these layers yet, but as a thicker slab develops above them, it will become more and more of a possibility. Dig down to investigate these weak layers before committing to steep slopes held onto old snow.