Persistent Slabs
- Alpine
- Treeline
- Below treeline
- Likelihood
- Unlikely
- Size
- 1.5–2.5
Triggering a large persistent slab avalanche on weak, sugary facets buried deeper in the snowpack would take some bad luck. The video to the right/above describes this problem. You are most likely to find this scenario on slopes with all or most of the following characteristics:
- Wind-swept alpine terrain, especially in the Pioneer, Boulder, and White Cloud Mountains
- Steeper than about 35 degrees
- Variable snowpack depths with areas less than 2 feet deep and/or rocks poking through the snow surface
- Large, hard wind features
Don't expect obvious signs of instability (snowpack collapsing or cracking) before a large avalanche releases. Snowpack stability tests are of little use in situations like this. The only way to effectively reduce the odds that you trigger one of these slides is to avoid terrain that checks all or most of the "boxes" above.