Cooke City

Very dangerous avalanche conditions exist near Cooke City. Heavy snowfall and very strong winds have pushed the snowpack to its breaking point. Tree-snapping monster avalanches will run long distances, much farther than you may expect. 

From Thursday morning to Friday night, several feet of snow has fallen with nearly 2.5 inches of water which is a very heavy load. Additionaly, snowfall rates for most of Friday were greater than 1 inch/hour which is extremely rapid loading. Strong to extreme winds have drifted recent new snow into thick slabs. These slabs can avalanche on their own and add weight to buried weak layers which could cause large to very large avalanches to break deeper.

Your best strategy is to avoid all avalanche terrain. This includes all slopes steeper than 30 degrees, and especially the lower angle terrain below steep slopes where massive avalanches can run out and pile debris many feet deep.

Dangerous avalanche conditions exist throughout the forecast area, and near Cooke City we issued an avalanche warning through at least tomorrow morning. Strong to extreme winds have drifted recent new snow into thick slabs. These slabs can avalanche on their own and add weight to buried weak layers which could cause large to very large avalanches to break deeper.

Near Cooke City the danger is HIGH on all slopes, and your best strategy is to avoid all avalanche terrain. This includes all slopes steeper than 30 degrees, and especially the lower angle terrain below steep slopes where massive avalanches can run out and pile debris many feet deep.

Near Bozeman, Big Sky and West Yellowstone the avalanche danger is CONSIDERABLE on middle and upper elevation slopes. Avalanches large enough to bury a person are likely on steep slopes, especially where the recent snow has been drifted into thicker, heavier slabs. Wind slab avalanches can be triggered that involve the recent drifts of snow, and larger persistent slab avalanches can break wider and deeper.

Yesterday near Island Park a group of riders reported widespread collapsing (observation) which is evidence that a person could easily trigger a persistent slab avalanche. Further north, near Big Sky and Bozeman the snowpack is deeper. Triggering a persistent slab avalanche may be more difficult, but the size will be larger. In the Bridger Range, the persistent weak layer is slightly less widespread. The main concern is large avalanches breaking within fresh drifts, but on the wrong slope these could break deeper in the snowpack (Dave's video from Saddle Peak).

Be extra cautious of slopes steeper than 30 degrees. Either avoid them entirely or very carefully assess the snowpack and consequences of a slide before entering avalanche terrain.