Persistent Slabs
- Alpine
- Treeline
- Below treeline
- Likelihood
- Possible
- Size
- 1–2
Yesterday, Sun Valley Heli Ski guides remotely-triggered a large avalanche in the Western Smokys. This slide exemplifies the nature of our persistent weak layer, and also demonstrates the concept of "remote triggering." While skiing low angle terrain, the group felt the snowpack collapse beneath them. This collapse propagated through the weak layer across the bowl and triggered an avalanche in steep, wind-loaded terrain 800-1000' away. Your reaction is probably the same as mine—yikes! You can see more details about the avalanche here.
This event follows on the heels of three separate slides that were triggered in the Galena Summit area December 26-27, as well as a cycle of large natural avalanches that occurred after the Solstice and Christmas storms. Suffice to say that we're not even close to out of the woods with this weak layer. In the Soldiers & Wood River Valley zone, we've just barely seen the opening acts.
Despite the overall decreasing likelihood of triggering a slide, the nature of our snowpack demands conservative terrain choices. Triggering an avalanche is more likely on steep slopes (over about 35 degrees) that have been affected by recent or past wind events, especially in the western portion of this zone where a thicker slab exists over the weak layer.
With a wet weather pattern in the forecast tonight through Tuesday, expect the avalanche danger to increase significantly over the next few days.
(1/1/2021) Sun Valley Heli Ski remotely triggered this avalanche from lower angled terrain 800-1000' away. The group felt a collapse that propagated across the bowl into steeper, wind-loaded terrain. Avalanche released on a 9400', E aspect in the Western Smokys. Photo courtesy of Sun Valley Heli Ski.