Persistent Slabs
- Alpine
- Treeline
- Below treeline
- Likelihood
- Possible
- Size
- 2
The primary avalanche problem is a weak layer of faceted snow from the December dry spell, buried on 12/25, about a foot below the surface on W-N-E-SE aspects. While the weak layer is widespread, the overlying slab is not—and both are needed to create an avalanche.
Westerly, northerly, and easterly aspects near treeline are most concerning, where cohesive slabs 1-2 feet deep are more consistent. You may transition from soft, weak snow or scoured terrain to standing atop a supportable slab resting on weak facets. Be cautious in gullies, depressions, and leeward terrain features, where slabs are more likely to form. Avalanches triggered 1-2 feet deep could step down to basal facets near the ground.
Above treeline, the likelihood of triggering an avalanche continues to decrease. Strong northerly winds have stripped snow from many aspects, leaving behind a stout wind crust that caps the weak layer on other aspects. This, combined with mid-pack and basal facets trending toward dormancy, reduces avalanche risk. However, thin, rocky slopes with shallow snowpacks above treeline should still be avoided.