Persistent Slabs
- Alpine
- Treeline
- Below treeline
- Likelihood
- Unlikely
- Size
- 1.5–2.5
Weak layers of snow are buried 2-4 feet deep in the Snake River range. Triggering a large hard slab avalanche at these depths has become unlikely, but is not impossible. A very large natural avalanche involving these layers occurred on January 7th and is a good reminder of weak snow lurking below. Triggering a persistent slab avalanche is most likely in very steep, north facing terrain where the snowpack is thinnest. Thin spots (trigger points) include wind-scoured slopes, cliff bands, and rocky areas. Obvious signs of instability, such as collapsing and cracking, may not be present prior to triggering a large avalanche.
Larger triggers such as groups, snowmobiles, or falling cornices, will increase the odds of impacting these weak layers. This avalanche problem is currently a low likelihood/high consequence scenario. Choosing terrain that reduces your exposure and remaining vigilant when traveling in avalanche terrain is important given this setup.
(1/16/2025)
An example of complex terrain in the Snake. Very steep, wind affected slopes where trigger points for a hard slab avalanche could be close to the surface.
Photo: Bridger-Teton Avalanche Center