Persistent Slabs
- Alpine
- Treeline
- Below treeline
- Likelihood
- Possible
- Size
- 1.5–3
Triggering a very large avalanche big enough to bury you is possible on steep, rocky, convex, or wind-loaded slopes over 35°. 2-3 feet of snow that fell this week sits on a variety of weak layers that were covered on January 31st. This 1/31 weak layer is widespread and consists of facets and crusts. Avalanches failing on the 1/31 interface could travel far distances (including above you) due to the widespread distribution and continuous nature of the overlying slab. Managing this problem will be difficult because signs of instability, such as collapsing, cracking, or recent avalanches, may not be present. Many slopes may appear stable due to the nature of the hard slab. Multiple tracks on a slope are not necessarily an indication that it is safe – it might take one more rider to find the trigger point. Choose conservative and lower-angle terrain to manage the dangerous high-consequence avalanche conditions.
Weak snow near the base of the snowpack lurks 3-6 feet below the surface. Loading from the recent storm snow is stressing these weak layers in locations that contain a shallower snowpack, such as the Wyoming Range. Avalanches involving these layers could occur with a significant trigger, such as a large avalanche triggered at the 1/31 interface. Keep these layers on your radar if traveling in shallow parts of the forecast zone.
(2/3/2025)
A large skier triggered avalanche on a NE facing slope at 9,400' south of JHMR. It likely failed on the new/old interface that was buried on 2/1. 7 skiers were caught and carried. All members of the party survived the incident.
Photo: Bridger-Teton Avalanche Center
