Persistent Slabs
- Alpine
- Treeline
- Below treeline
- Likelihood
- Likely
- Size
- 2–3
Triggering a very large avalanche is a worrisome possibility. Some of these slides will be powerful enough to destroy a house. A week of heavy snowfall is stressing weak layers near the base of the snowpack. These layers of facets and/or surface hoar on shadier aspects and crust + facet combinations on sunnier slopes are fragile and can be found on most slopes.
The odds you trigger a Persistent Slab are decreasing, but the consequences remain severe. These avalanches can break in surprising ways. Don't expect obvious signs of instability, like cracking or collapsing before triggering a slide. You can trigger them from flat or low-angle terrain long distances away from steep slopes. The only way to manage this problem is to avoid avalanche terrain, including the base of slopes that are threatened from above.