Persistent Slabs
- Alta quota
- Limite del bosco
- Sotto il limite del bosco
- Probabilità
- Possible
- Dimensione
- 1.5–3
Expect to find 1-2 foot thick slabs in areas sheltered from the wind. The slab may be twice as thick in terrain affected by the wind. These avalanches have failed on various weak layers: facets and/or surface hoar on shadier aspects and crust + facet combinations on sunnier slopes. Large natural and human-triggered avalanches have occurred on several aspects in recent weeks. Assume this problem exists on all upper and middle elevation slopes and on shadier, lower elevation aspects.
Avalanches on this uncommonly widespread and fragile layer will break widely and in surprising ways. Don't expect obvious signs of instability, like snowpack cracking and collapsing. Your first sign of trouble may be the destructive avalanche you trigger. These slides can be triggered from long distances away—from flat or gentle terrain below, above, or to the sides of steep slopes.
(1/26/2024) This enormous avalanche failed above the N Fk of the Big Wood River. The set of crowns that produced it spread across over a mile of terrain and these slides deposited debris in 4 separate alpine bowls. Based on the location and the appearance of the crown, these slides likely failed on a crust with associated facets. The crown pictured here faces SE-S-SW between 9,300 and 10,000'.