Persistent Slabs
- Alpine
- Treeline
- Below treeline
- Likelihood
- Likely
- Size
- 1–2
Triggering a dangerous avalanche involving buried weak layers is likely today in steep terrain above 30°. Weak snow formed in early December is now buried ~2 feet deep in many locations and up to 4 feet deep in wind-loaded upper-elevation terrain. Avalanches involving these weak layers have been reported on most aspects at all elevations.
Obvious signs of instability may not be present before triggering a persistent slab avalanche. Slabs could be triggered from a distance by the first rider or even wait until the last person in your group is riding the slope to release. Steep, rocky, and unsupported terrain features are most likely to produce an avalanche. However, given the well-connected nature of the weak layer, avalanches can propagate long distances across slopes. Because of this, avoid terrain connected to avalanche paths, beware of what lies above you, and give runout zones a wide margin. Remote triggers were reported as recently. Evaluating your travel plan carefully is essential when avalanches behave like this. Give tight gullies, creek drainages, tightly treed chutes, and other terrain traps a wide margin. For now, riding low-angle terrain less than 30° with no significant overhead hazard is the best way to avoid this problem.
(1/5/2025)
Looking up from the burial site at the remotely-triggered large avalanche off the west shoulder of Brooks Lake Mountain near Breccia.
Photo: Bridger-Teton Avalanche Center