Persistent Slabs
- Alta quota
- Limite del bosco
- Sotto il limite del bosco
- Probabilità
- Possible
- Dimensione
- 1.5–2.5
Triggering a large avalanche up to 2 feet thick is possible where weak layers have been buried since the beginning of February. The current slab sits on a variety of weak surfaces, including crusts/facets on solar aspects and facets on shady aspects. This problem could be sensitive to the weight of a single rider or snowmobile. You are most likely to trigger an avalanche on very steep rocky slopes and areas where wind deposited snow from the last storm into firm slabs. Specifically, consider where the overlying slab might be thin and where you can more easily impact weak layers below - such as around the margins of wind-loaded slopes. Large triggers like snowmobiles, cornices, and small avalanches in more recent snow will increase the likelihood of triggering a large avalanche. Dig down and investigate layers in the top two feet of the snowpack, but keep in mind that buried weak layers from the January dry period will be as deep as 4 feet in wind-loaded areas and will not show any signs of instability like cracking or collapsing until an avalanche is triggered. Continue to travel safely by going one at a time around steep avalanche terrain and spacing out around terrain traps like creek beds and gullies.
Weak layers left over from dry and cold December weather remain buried up to 5 feet on west through north through east aspects above 9000'. It is unlikely that you will impact these layers and there will be no signs or indication of this problem while travelling. Travel where the snowpack is deep by avoiding thin rocky areas and slab margins.
(2/11/2025)
The crown of the recent unintentionally-triggered avalanche on the E face of Lava ~10,400'.
While unlikely that you will trigger an avalanche this large, it is a good reminder of the current situation involving buried weak layers and high consequences.
Photo: Bridger-Teton Avalanche Center