Bridger Range

Wind slabs are generally small and have time to stabilize, but there may be a few unstable wind slabs in isolated areas. If you venture onto steep slopes, be alert for previously formed drifts of snow, especially in terrain where the consequences of a slide are increased due to trees, cliffs or steep, rocky slopes. Allow only one rider at a time on steep slopes while a partner watches from a safe spot, and make sure everyone is carrying functional rescue gear of a beacon, shovel, and probe.

Avalanches are unlikely and avalanche danger is LOW through the forecast area with the exception of upper elevations in the Lionhead Area near West Yellowstone where danger is MODERATE. Although unlikely, there are two avalanche problems to keep in mind. 

The last persistent slab avalanches were just over a week ago in the Lionhead area (observation), which is cause for slightly higher concern there, and three weeks ago in the Southern Madison and Southern Gallatin Ranges (observation). The chances are low to trigger one of these avalanches that breaks on weak snow near the bottom of the snowpack, but the size and consequences could be large. 

The persistent slab avalanche problem will probably not show warning signs like collapsing, or unstable snowpack test results. Therefore, terrain choice and following normal safe travel protocols are your best strategies to stay safe. Be cautious of big, wind-loaded slopes near high ridgelines where snow depth is variable and you might hit a shallow spot and affect the weak layer (Mark’s video from Island Park and my video from Lionhead). 

Wind slab avalanches are an additional problem to keep in mind. Earlier in the week, strong winds drifted any existing soft snow into stiffer slabs. On Friday, skiers in Hyalite adjusted their plans when they found a questionable drift in high consequence terrain (observation). There were also recent wind slab avalanches reported near Cooke City (observation) and Island Park (observation), and yesterday we went to the Bridger Range and saw a few wind slab avalanches that happened 2-3 days prior (observation, video). 

Recently formed wind slabs are generally small and have had time to stabilize, but there may be a few unstable drifts in isolated areas. Recent clear skies and cold nights weakened the surface of the snowpack which might contribute to a wind slab remaining unstable today if it rests on this weak snow. If you venture onto steep slopes, be alert for previously formed drifts of snow, especially in terrain where the consequences of a slide are increased due to trees, cliffs or steep, rocky slopes.

Allow only one rider at a time on steep slopes while a partner watches from a safe spot, and make sure everyone is carrying functional rescue gear of a beacon, shovel, and probe.

Old news, but noteworthy: Yesterday Mark was in Island Park and found the remnants of nine big, destructive avalanches (observation). These probably occurred in late December when the area received heavy snowfall and rain. They initiated near 8,600’ elevation, and the debris looked like wet avalanche debris, indicating the slides were probably mostly wet upper snowpack failing on the weak layer near the ground.