Cooke City

Avalanches can be triggered by a person, breaking up to 2 feet deep on weak layers that formed in January and early February. Avalanches are most likely on wind-loaded slopes, but also possible on slopes sheltered from the wind. If you seek out steep terrain, steer clear of recently wind-loaded slopes and carefully assess the snowpack for buried weak layers. Choose smaller slopes and slopes that do not have terrain traps like cliffs, trees, or confined gullies.

The main avalanche problem to watch for is persistent slab avalanches that break up to 2 feet deep, failing on weak layers that formed in January and early February. This problem is more widespread in areas that received the most snow over the last couple weeks, like near Island Park, West Yellowstone and Cooke City.

Last week near Island Park and West Yellowstone there were eight human-triggered avalanches, and five of those caught and buried snowmobilers (avalanche observations). Near Cooke City, over the weekend I saw recent natural avalanches, and a few human-triggered avalanches that broke as recently as Saturday (observation).

Near Big Sky and south of Bozeman, in the Northern Madison and Northern Gallatin Ranges, less snow fell over the last couple weeks and we haven’t heard of much avalanche activity. However, there have been many observations of weak, sugary facets and surface hoar buried up to a foot deep below the last couple week’s snow (Beehive Observation, Buck Ridge observation). These buried weak layers make avalanches possible, especially on slopes where recent strong winds drifted snow into thicker slabs. An avalanche last Friday on Buck Ridge is an example.

Wind was strong out of the southwest at the end of last week which affected many slopes, stripping snow off some and loading others with thick drifts (Cooke City video). This makes avalanches most likely on wind-loaded slopes, but persistent slab avalanches are also possible on slopes sheltered from the wind. Wind slab avalanches involving recently drifted snow are unlikely where they are not sitting on a weak layer, as they have had a couple days to stabilize, but any recent drifts still deserve caution today.

If you seek out steep terrain, steer clear of recently wind-loaded slopes and carefully assess the snowpack for buried weak layers. Choose smaller slopes and slopes that do not have terrain traps like cliffs, trees, or confined gullies.

The Bridger Range received the least recent snowfall in our forecast area and avalanches are unlikely. Stay alert for a drift or two that might remain unstable, especially where even a small slide would have large consequences, like above cliffs, trees, or other terrain traps. There are also weak layers buried up to a foot deep here, but we have not seen evidence they are a problem yet (observation, observation). If you plan to ride steep terrain, dig down a couple feet and check for weak layers or unstable wind slabs.

Avalanche danger is MODERATE throughout the forecast area, except in the Bridger Range where avalanche danger is LOW.