Persistent Slabs
- Alta quota
- Limite del bosco
- Sotto il limite del bosco
- Probabilità
- Likely
- Dimensione
- 2–3
Recently numerous naturally tiggered persistent slab avalanches released through Thompson Pass as well as areas further from the road. Many of these involved impressive propagation lengths with the N Catchers Mitt slide being almost a mile wide (see pictures). These long and erratic fracture lines are a good indicator that a persistent weak layer is responsible for the activity. This type of problem can remain reactive much longer than typical storm snow instabilities. We are keeping the hazard elevated until we gain more information recarding the sensitivity of this problem.
It will remain likely for a person to trigger a large widely propagating avalanche, 2-3 feet deep, in steep alpine terrain today. We recommend limiting travel to simple terrain under 32 degrees that is not connected to or underneath avalanche terrain.
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 when travelling on or below terrain over 32 degrees.
Windslab: Wind stiffened or slabby snow in specific areas will likley make this problem more sensitive.
(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