Persistent Slabs
- Alpine
- Treeline
- Below treeline
- Likelihood
- Possible
- Size
- 1–2
Hard slabs 1-3 feet deep lie above weak snow formed in early December. As the likelihood of triggering an avalanche on these buried weak layers decreases over the time, the possibility remains. This includes triggering from a distance or below the slope. The last human triggered avalanche involving these weak layers occurred on January 4th and was remotely triggered from below. Slopes that contain thin, sensitive areas in the slab are the most likely places to impact these layers. Thin spots usually exist around very steep, rocky, and wind blown terrain features. Deeper slabs with larger consequences exist in the upper elevations.
Large triggers in the form of groups, trenching a snowmobile, and falling cornices will increase the odds of impacting these layers. Use safe travel practices in order to minimize your exposure to this problem. Travel one at a time across steep terrain, avoid dangerous terrain traps, and communicate plans with your group members throughout the day.
(1/16/2025)
An example of terrain where persistent slab avalanches are most likely.
Photo: Bridger-Teton Avalanche Center