Deep Persistent Slabs
- Alpine
- Treeline
- Below treeline
- Likelihood
- Unlikely
- Size
- 1
The 1 to 2 inches of snow expected today should not provide enough additional weight to make persistent slabs a more widespread problem. In most areas triggering a persistent slab avalanche will remain unlikely because the persistent weak layer has either become wet and mostly refrozen or it has become denser and adjusted to the weight of the current snowpack above it. However, this layer still lingers on some NW-N-NE aspects and triggering a persistent slab avalanche is not impossible on some isolated terrain features. Open slopes sheltered from this winter's NE winds at elevations above 8000 ft. represent the best places to find lingering instability. More complex terrain like sheltered, shady couloirs, steep rocky slopes, or slopes with steep convex roll-overs where the persistent weak layer remains weak could also be suspect. If more snow falls than forecasted, persistent slabs could become more widespread and easier to trigger.
Tools like quick snowpit tests, handpits, and probing can help identify those isolated areas where the persistent weak layer may still exist. Avoiding those isolated areas where instability may linger and slopes connected to those areas still remains a prudent choice. If one of these isolated areas were to release, it could release above the person who triggers it and it may not release until that trigger fully commits to the slope. This weak layer is more likely to exist in the mid to lower part of a slope and so evaluating the slope from the traditional start zone at the top of a slope may not provide a meaningful or accurate assessment.
