Cooke City

New and wind-drifted snow are loading slopes with unstable slabs, making human-triggered avalanches breaking one to two feet deep likely. Isolated instability on steep rocky slopes with thin spots could still result in a very large avalanche. Seek out terrain sheltered from the wind and slopes with a uniformly deep snowpack.

Yesterday in the Lionhead Area, Mark and I walked toward the crown of an avalanche that broke a week ago, heard a “whumph,” saw cracks shoot through the 15-20” of recent snow, and watched the slope avalanche for a second time (observation and video). New and wind-drifted snow are loading slopes with unstable wind- and storm-slabs, making human-triggered avalanches likely in steep terrain of the Southern Madison and Southern Gallatin Ranges and the Lionhead and Island Park Areas.

Ian observed many persistent slab avalanches in the Lionhead Area last week (video,observation), and Alex noted similarly weak layers in the Taylor Fork (video,observation). Higher elevations harbor weaker snow than the lower elevations. There is reason for optimism about basal weak layers and persistent slab avalanches moving forward, but don’t push it. Step back from steep terrain while this week’s snowstorm plays out. The danger is CONSIDERABLE in the Southern Madison and Southern Gallatin Ranges and the Lionhead and Island Park Areas.

In Cooke City, the primary concern is wind slab avalanches. Increasing winds will transport recent snow into reactive slabs up to two feet deep. Avoid wind-loaded slopes below corniced ridgelines and where you observe signs of drifting and instability, such as stiff or textured snow surfaces, shooting cracks, and recent avalanche activity.  

Triggering a persistent slab avalanche on basal weak layers is unlikely, as deep snow keeps skiers and riders far above the problematic layers. However, a very large avalanche could occur if a person finds just the wrong thin spot on rocky slopes or near cliff bands. Seek out wind-sheltered terrain with a uniformly deep snowpack where avalanches are much less likely. The danger is CONSIDERABLE on wind-loaded slopes at mid- and upper-elevations in Cooke City.

With less recent snowfall, the primary avalanche concern in the Northern Madison, Northern Gallatin, and Bridger Ranges is wind slab avalanches on freshly drifted slopes. Avalanches will generally be less than one foot deep and most concerning in upper-elevation terrain below corniced ridgelines and near windbreaks such as gullies and trees. Slides on Mount Blackmore and in thenorthern Bridger Range are good examples. Seek out wind-sheltered terrain and don’t underestimate the power of relatively small avalanches, especially with the addition of terrain traps.

Triggering a persistent slab avalanche is unlikely for now. The danger is MODERATE at upper elevations in the Northern Madison, Northern Gallatin, and Bridger Ranges on wind-loaded slopes, and LOW at lower elevations.