Persistent Slabs
- Hochgebirge
- Waldgrenze
- Unterhalb der Waldgrenze
- Wahrscheinlichkeit
- Very Likely
- Größe
- 2
Continued snow and wind are building 3 to 4-foot cohesive slabs on the surface over several faceted weak layers deeper down in the snowpack. Recent natural and human triggered persistent slab avalanches is a good indication that the added weight of the new snow over the last three days has greatly stressed the faceted persistent weak layers. There are several faceted weak layers of concern in the snowpack with the most likely weak layer to trigger being the buried near-surface facets that formed during the 3 week high-pressure period before these storms. Below treeline, slabs rest on top of an entirely faceted snowpack to the ground. A persistent slab avalanche that initially fails in an upper faceted weak layer has a chance to step down into deeper faceted weak layers creating a larger unsurvivable avalanche.
Pay attention to obvious signs of instability like collapsing and shooting cracks. You can trigger a persistent slab avalanche from the flats below or adjacent slopes. Stay off of or underneath slopes that are greater than 30 degrees as we may see avalanches running long distances today.
Remotely triggered persistent slab avalanche from well below the crown on 1/25. This avalanche failed on facets near the ground.