Persistent Slabs
- Alpine
- Treeline
- Below treeline
- Likelihood
- Likely
- Size
- 3
It’s been more than ten days since the last storm and avalanche cycle. Obvious red flags like collapsing and cracking have faded, but the underlying snowpack structure remains poor. Despite warm temperatures and a deceptively stable-looking surface, weak faceted layers are still present below.
On northerly aspects near and above treeline, thick hard slabs—2 to 4 feet deep—rest on top of these persistent weak layers. They’ve grown more stubborn, but if triggered, they have the potential to fail deeply and step down through much of the season’s snowpack.
Thin, rocky areas, steep convex rollovers, and slope margins remain likely trigger points. When the payoff for riding steep terrain is minimal, it’s hard to justify the risk. My approach continues to be simple: avoid steep slopes in this terrain altogether.
Results of an extended column test on a northeast aspect at 10,800 feet, at the upper end of our "below treeline" elevation band. Score was ECTP25 failing on the Feb 11, persistent weak layer. This indicates that avalanches are growing more stubborn to release, but that they are still clearly possible. It's getting to where finding the right trigger point, such as a shallower area on the slab is what it will take. The danger increases with elevation.
