Persistent Slabs
- Alpine
- Treeline
- Below treeline
- Likelihood
- Likely
- Size
- 3
A slab of cohesive snow now exists above a persistent weak layer of faceted snow on all aspects. This weak layer formed during the December dry spell. Red flag indicators of instability have been obvious during field work Sunday and Monday. Collapsing of the snowpack has been widespread at all elevations, snow pit tests continue to produce propagation, and large, remotely triggered avalanches show us how unstable things really are. The writing is on the wall, and it says we have a dangerous snowpack.
The Horse Creek avalanche is a great example of the snowpack structure in alpine terrain. Large, hard slabs of wind-drifted snow rest on top weak, faceted snow, and they are hanging in the balance just waiting for a trigger. Slopes like these present the most danger. The danger is not limited to Northerly aspects, as we have started to see collapsing and poor pit results on Southerly slopes as well.