Persistent Slabs
- Alpine
- Treeline
- Below treeline
- Likelihood
- Possible
- Size
- 1.5–2.5
The recipe for avalanches (slab+weak layer) exists in many places. Facets and facet+crust combinations are buried underneath dense, 1.5-2.5 foot thick slabs. This pairing is capable of producing large, destructive avalanches. You'll find this snowpack structure on all upper elevation slopes and shaded middle elevation slopes (W-NW-N-NE-N).
As you're traveling, look for obvious signs of instability such as cracking and collapsing. Pay attention to these warnings, but don't let a lack of them lull you into a false sense of security. These types of weak layers can produce avalanches long after loading events. You can dramatically reduce your risk of tangling with a large avalanche by avoiding slopes where this weak snow exists at the base of the snowpack.