Three backcountry skiers effectively used their two-way radios last month to instantly communicate the moment an avalanche triggered and began to slide. It’s a good example of the isolated danger of triggering Persistent Slab avalanches. And a great example of safe backcountry travel protocols.
Finn Kelly’s group accessed* the Adam Mountain backcountry skiing and splitboarding from the standard route from No Name Creek to the Adam’s Rib zone south of Eagle, Colorado. The Adam’s Rib slide was indeed small on a low angle slope, yet carried all the characteristics of a Persistent Slab avalanche.
#unepicadventures: Watch video of skier-triggered avalanche in the Aspen Zone, 3/11/17, and listen to the group’s radio communications. Shot by Finn Kelly.
Persistent Slabs form when a persistent weak layer is buried by additional layers of snow. The problem persists after storm and wind slab instabilities have stabilized. The persistent weak layer can cycle through periods of sensitivity from reactive to nonreactive due to changes in weather conditions such as new precipitation, wind loading, strong solar radiation, and/or rapid changes in air temperature.
The best ways to manage the risk from Persistent Slabs is to make conservative terrain choices. They can be triggered by light loads and weeks after the last storm. The slabs often propagate in surprising and unpredictable ways. This makes this problem difficult to predict and manage and requires a wide safety buffer to handle the uncertainty.
Finn Kelly reports: “One of my favourite things to do is backcountry skiing. Unfortunately there are huge risks that come with this fun. Recently on an #unepicadventure, we experienced this risk by triggering an avalanche.”
Finn and friends recently experienced this backcountry risk by triggering an avalanche on Adam Mountain in Eagle, CO. But due to proper safety precautions, including traveling with radios for group communications, they were able to mitigate the avalanche risk and get out of harm’s way.
“I have always said the radio is one of the greatest avalanche safety tools you can have and you can see why here in this video,” says Finn. “Who knows what would have happened to Morita Levis if we did not have our radios.”
Thanks to Aaron Batte for sharing the incident with BCA. And, we are pleased that the group also shared their experience with the Colorado Avalanche Information Center (CAIC), which published his avalanche incident report.
Avalanche Incident Report: Adam’s Rib zone south of Eagle
Observer: Aaron Batte
Backcountry (BC) Zone: Aspen
Weather Description: Warm conditions, sunny, no wind, 40+ degree temp. East aspect, elevation 11,140′
Snowpack Description: Highly variable. We encountered a few spots of light powder and some corn, but mostly a freeze/thaw effected breakable crust top layer all sitting on top of a 18″-23″ deep hard persistent layer.
Avalanche Description: R2, D2 Persistent Slab slide on East facing aspect of Adam Mountain. 20″ depth at crown, 120′-150′ across at fracture. Heavy wet snow in the layer above the slab caused a slow moving slide. Party of 4, 3 skiers 1 snowshoer. We approached the Adam’s Rib area via No Name Creek with the intent to ski the east facing aspect of Adam Mountain. With the snowshoer in a safe zone at treeline, the first skier began a descent from near the summit into the first, east facing bowl. On the third turn an avalanche was triggered from above. We were able to communicate the avalanche to the skier via BC Link radios and the skier stopped skiing in a safe area to the skiers right of the slide path. All 3 skiers were trained and had proper equipment; in this instance the radio was our most critical piece of safety gear. Video: https://youtu.be/QXguhwc3oHc
Avalanche Area Description: Adam Mountain, slide path/ run closest to summit.
- Elevation: 11000 ft
- Maximum Crown: 20 in
- Maximum Width: 150 ft
- Maximum Vertical: 250 ft
Comments: Slide released above and behind first skier. Occurred about 2:20 pm.
Backcountry Access recommends sharing all avalanche incidents and signs of activity with local avalanche centers to alert other backcountry users of dangerous conditions.
*How to Access the Adam’s Rib Backcountry
You’ll be setting your own skin track, but once it’s in, you’re good to go. From the summit of Adam Mountain, there are incredible views of the Elk and Gore mountains. Five gullies and avalanche chutes are located on the face of Adam Mountain, which curves from south-facing to south to southeast to east-facing. The northern slope of the mountain is mellow, but gullies and avalanche chutes on the southeast face offer amazing descents. As long as the snowpack is stable, these runs offers great slope angle and aspect, lots of vertical and lots of runs.