Persistent Slabs
- Alpine
- Treeline
- Below treeline
- Likelihood
- Likely
- Size
- 2–3
We have multiple persistent weak layers in our snowpack at the moment. The most concerning layer is a thin layer of faceted snow that has resulted in several large natural avalaches over the last 36 hours. Recent snowfall has burried this layer 1-3 feet deep in many areas above 3000 feet causing the potential for large destructive avalanches. With these types of avalanches long irregular fracture propagation can effect terrain quite some distance from the trigger point including lower angle slopes. To make things more complicated, signs of instability underfoot may be absent even though hazardous conditions exist. The best way to deal with this problem is by carefully managing the terrain you travel on as well as your exposure from above.
Burried surface hoar formed on 1/26 has recentely been found up to 3800 feet in the continental zone. Large well preserved "upright" surface hoar burried 1-2 feet deep has been reactive in pit tests but has not recently produced avalanche activity. We will likely see increased sensitivity with this layer in the Continental zone with new snow loads or changes in slab character.
An additional weak layer of facets at the bottom of a thin snowpack below 3000 feet is showing reactivity in pit tests. We have yet to see any recent avalanche activity on this layer but it could become more of a concern with additional loading or changes in the overlying slab.
Caution is advised on all terrain over 32 degrees.
Due to the nature of persistent weak layers this problem is not likely to go away quickly.
(2/13/2026)
Naturally triggered persistent slab on N oddessey. The long irregular fracture line that crosses terrain features is an indicator of a burried persistent weak layer.
Photo: Joshua McDonald