Persistent Slabs
- Alpine
- Treeline
- Below treeline
- Likelihood
- Possible
- Size
- 3
I'm still avoiding steep north facing slopes at upper elevations where a person might trigger a dangerous deep slab avalanche breaking on a persistent weak layer near the ground. Although they have become much less likely and harder to trigger, very dangerous deep hard slab avalanches remain possible on northerly facing slopes above about 8000' in elevation. These slopes have a layer of weak, sugary facets near the ground that could fracture and produce slab avalanches several feet deep and hundreds of feet across. The danger of deep slab avalanches failing on a persistent weak layer is diminishing as the snow pack continues to deepen and gain weight, and the sugary faceted snow is compressed into the ground features. However in some isolated areas, ( especially in areas where the snowpack is shallower), avalanches might be triggered remotely, from a distance, or from flatter terrain under steep slopes. Yesterday, I found weak faceted snow at the bottom of the snowpack on a shallow (previously scoured) west facing slope in the Beaver Mountain Backcountry.