Island Park

Recently wind-loaded slopes below corniced ridgelines are the most likely place to encounter trouble. Consider terrain features such as cliffs, rocks, and trees that increase the risk of being caught in a small slide, as avalanches will generally be less than a foot deep. Seek out terrain sheltered from the wind and step back from steeper slopes if you observe cracking, collapsing, or recent avalanches.

It’s time to brush off any avalanche cobwebs that formed during the last month. Yesterday, skiers triggered a storm slab avalanche in Wolverine Bowl in the Bridger Range that broke 10” deep and 50 feet wide (details and photos, more info), and ski guides in Cooke City observed shooting cracks and heard one audible whumph as weak layers collapsed (details). Local ski patrols doing avalanche mitigation work triggered many slides around one-foot-deep, breaking within the storm snow, and some that broke up to 24” deep on weak layers in the upper snowpack.

Wind slab avalanches on steep slopes that got wind loaded during yesterday’s storm are the primary concern. With calm winds today, conservative terrain selection is warranted on and around commonly wind-loaded slopes that are at upper elevations, below cornices, and around wind breaks, such as gullies, rollovers, and tree fences. Encountering shooting cracks, audible collapsing, textured snow surfaces, obvious drifts, and stiffening surface conditions are additional warning signs that should prompt backcountry travelers to ease back to lower-angle terrain.

Persistent slab avalanches are going to be trickier and could occur on slopes with more than about 10” of new snow. They are the most likely and would be the largest where weak layers overlap with wind-loaded terrain. Yesterday, in the Taylor Fork, I found the critical recipe of a slab of cohesive snow sitting on our weak layer of concern, which resulted in quite unstable test scores (Taylor Fork video). Assume the weak layer is present throughout the forecast area, be watching and listening for signs of instability, and dig two feet deep (a foot into the old snow) to assess and test weak layers before considering any slope steeper than 30 degrees. Without additional loading, I expect this concern to diminish quickly, only to resurface with the next storm.

Persistent slab avalanches are not currently an issue in areas that received less snow yesterday, including Lionhead and Island Park. Focus on higher-elevation, wind-loaded terrain as the primary area of concern.

The danger is rated MODERATE throughout the forecast area.