Persistent Slabs
- Alpine
- Treeline
- Below treeline
- Likelihood
- Very Likely
- Size
- 4
The most dangerous and likely problem is large slab avalanches breaking on persistent weak layers near the ground. These slides will be 3-5 feet deep and hundreds of feet wide. Today these avalanches are very likely on slopes loaded by strong southwest and west winds.
These persistent weak layers exist on all west, north, east, and southeast facing terrain. Yesterday I triggered collapses and cracks shooting 100 feet in front of me as I rode near the top of a 29 degree, southeast facing slope (photo and video below). If it had been just a few degrees steeper, it would have produced an avalanche.
Here's the tricky part about this avalanche problem - Places with a thick, hard slab on top of this weak layer will be a little harder to trigger and it may be the 1st or 2nd or even 10th person on a slope who triggers it. The main point is that tracks on a slope DO NOT mean it is stable.