Persistent Slabs
- Alta montaña
- Límite del bosque
- Bajo el límite del bosque
- Probabilidad
- Possible
- Tamaño
- 1–2.5
A month of dry weather created a weak and faceted snowpack in many places throughout the forecast area. The poorest structure exists near and above treeline on NW, N and E aspects. From 2/10 -2/12, the region received 6-24" of new snow. Thus far, we've seen few results on buried, old snow. The problem with persistent grains is that they persist. Facets and depth hoar do not follow the same stabilization trends as storm instabilities, and feedback may be limited until an avalanche occurs. Furthermore, persistent slab avalanches can be remotely triggered, fracture higher into lower-angle terrain, and connect around terrain features that would otherwise confine different avalanche problems.
We have lower confidence around this problem. In most places, it would seem that the new snow has not yet formed a slab capable of creating an avalanche. Increased wind, settlement, and warming could be enough to increase slab strength.
Remote triggers, shooting cracks, and "rolling" collapses that seem to continue off into the distance are all signs that you have likely found the persistent slab avalanche problem.
In times of heightened uncertainty, a tried and true risk management strategy is to increase your safety margins. Currently, you can do that by treating polar slopes near and above treeline with more suspicion than you would with a storm or wind slab problem.