Persistent Slabs
- Hochgebirge
- Waldgrenze
- Unterhalb der Waldgrenze
- Wahrscheinlichkeit
- Possible
- Größe
- 4
The odds of triggering an avalanche breaking near the ground on an old persistent weak layer are drastically different from one slope to the next. Many slopes have a deep and relatively strong snowpack where triggering one of these slides is unlikely. On other slopes, the odds are very high. In the case of Craig's avalanches yesterday, they didn't even have to get onto the slope to trigger it.
Chad and his partner were skiing in upper Weber Canyon where they described it as a "tale of two snowpacks". Most areas had deep snow until they walked onto a slope with just over 3 feet of total snow and they triggered the largest collapse they had every experienced with cracks shooting 150 feet from them (video below).
To avoid this problem, you'll have to be a detective to identity areas with thin snow. Notice the rocky area in the left side of the photo of Craig's avalanche. Steep rocky areas are often areas that may have a much thinner snowpack.