Persistent Slabs
- Alpin
- Limite forestière
- Sous la limite forestière
- Probabilité
- Unlikely
- Taille
- 1.5–2.5
While unlikely, we can't write off triggering large avalanches. There are two sets of weak interfaces to be aware of:
- Rain crusts or crust + facet combinations—Found in the upper half of the snowpack on most middle elevation slopes. Evidence suggests that these are healing, but their high variability with elevation and aspect makes their behavior hard to predict.
- Weak sugary facets—Found near the ground on middle and upper elevation slopes, especially those facing away from the sun. Triggering a slide on this layer is most likely in windy and/or rocky areas where the snowpack depth is variable and in more sheltered terrain where the snowpack is around 3 feet deep.
You can reduce the chances of triggering these avalanches by avoiding steep, wind-affected, or rocky slopes.
Additional Discussion: You may be able to trigger wind slab avalanches that formed near ridgelines and in cross-loaded areas on the sides of gullies. Look for recent cornice growth, dunes, or ripples in the snow surface. These are signs the wind has been at work, transporting snow.
(12/28/2025) Large natural avalanches. Paradise Peak and West Fork Big Creek. Photo: Sawtooth Avalanche Center