Deep Persistent Slabs
- Hochgebirge
- Waldgrenze
- Unterhalb der Waldgrenze
- Wahrscheinlichkeit
- Possible
- Größe
- 2–3
Above 3,500’, the base of the snowpack is a variable patchwork of old wind slabs sitting over facets (weak, sugary snow). These old wind slabs remain strong and continue to bridge the weak snow near the ground. Observations still show a generally stronger snowpack at upper elevations than at mid elevations, where the basal weak layer is more developed.
Our concern is that a person could trigger a deep, hard slab avalanche where the wind slab is thinner or absent and the weak layer is closer to the surface. This problem is difficult to assess because these thinner “trigger points” can be small and hard to identify. You can reduce your risk by avoiding large, steep alpine faces with thin, rocky areas. You can avoid this problem by choosing terrain under 30°.
This problem is expected to have a higher sensitivity and likelihood in the Continental zone.
(1/23/2026)
Large connected natural hard slab avalanche associated with our deep persistent weak layer. Mt Dimond north face
Photo: Gareth Brown