Persistent Slabs
- Alpine
- Treeline
- Below treeline
- Likelihood
- Possible
- Size
- 1–2
Old November snow near the ground is weak and has formed the foundation of our seasonal snowpack. Atop this weak snow rests a slab of denser snow from earlier this month. This indicates poor structure that is a classic recipe to produce avalanches. This weak snow is buried anywhere from 1.5-2 feet below the surface. You're most likely to find this poor structure on steeper slopes that face away from the sun. Think of any terrain that held snow through November. Unfortunately, these areas are the same slopes where people want to recreate because of the deeper snow. On other aspects with the slightest bit of solar influence, this weak snow is stronger and the overlying slab is broken up by crusts and softer snow.
With persistent slab problems, sometimes the best management strategy is avoidance. Careful consideration of shaded E,NE,N,NW, and W slopes above 7000' is necessary to safely travel in the mountains right now.
(12/20/2023) ECTP 13 on a N/NW aspect at 7200 55 cm below the surface. Failed in the weak snow near the ground. Photo: Kevin Studley