Persistent Slabs
- Alta quota
- Limite del bosco
- Sotto il limite del bosco
- Probabilità
- Likely
- Dimensione
- 1–2
There are two primary buried layers of concern making up our persistent slab problem. The most reactive and concerning is surface hoar that was buried and preserved on February 14th. This layer is worst at upper elevation on northerly or shaded slopes where human triggered avalanches are likely. At mid elevation and on south aspects, the layer is present but less continuous and less reactive but still possible to trigger an avalanche on. The second layer of concern is a lower layer of buried surface hoar and near surface facets from late January. This layer is showing less reactive, but still is not trustworthy.
Another factor affecting the avalanche problem is slab thickness and density. You are more likely to trigger an avalanche in areas with a thicker or harder slab like wind drifted terrain where a larger slab is present. Don't ignore areas with a thinner slab though, as they are still capable of avalanching.
Here is an example of a human triggered avalanche on this layer. Check out the observation page for a full list of recent avalanches and unstable snowpack observations.
You may not see obvious red flags like cracking, collapsing or whumfing before triggering an avalanche. To identify the problems, dig in the snow. Buried surface hoar will present as a thin grey line running across the snowpit wall. Dig quick pits in multiple locations as surface hoar is highly spatially variable.
If you find buried surface hoar, do not trust it. Surface hoar is an especially nasty buried weak layer and can produce avalanches on low angle slopes down to 30 degrees in slope angle.
(2/19/2026)
Buried surface hoar under 10 inches of recent snow.
Photo: Cam Mackenzie