Persistent Slabs
- Alpine
- Treeline
- Below treeline
- Likelihood
- Unlikely
- Size
- 2–3
Weak snow near the ground forms the base of the snowpack in many places in this zone. This remnant snow from October exists on shaded slopes (NW-N-NE-E) at middle elevations and most slopes at upper elevations. We are two and a half weeks out from a significant loading event in this zone and the chances of triggering a large avalanche involving this snow have gradually decreased with each passing day. However, many experienced backcountry travelers and local professionals continue to give slopes with this snow at the base of the snowpack a wide berth. Even though I love playing in the steep terrain that exists in much of this zone, I'm happy to count myself amongst that group. If I were to go out looking for this problem today, this is the type of terrain I'd head for:
- Steep: slopes about 35 degrees and steeper
- Rocky: slopes with variable snow cover due to the roughness of the terrain
- Wind-affected: slopes where strong winds produced variable snow cover due to scouring and loading
If you go into terrain that looks like what I just described it isn't likely that you are going to trigger a large avalanche. But it is a long way from impossible. The choice of what type of terrain you enter on any given day is up to you, but it is important that you are honest with yourself about the types of risks you are taking by doing so, no matter how unlikely they may be. For me personally, I'll be continuing to avoid the terrain in this zone where this problem exists.
ADDITIONAL DISCUSSION As days pass without significant loading, the recent batch of wind slabs has become less reactive. However, If I headed out skiing or riding in upper elevation terrain in this area today I'd still be paying attention to these slabs. These slabs are sitting on a few different weak snow surfaces such as facets, crusts with facets, and surface hoar. These types of weak snow are slow to heal and can cause avalanches days to weeks after they have been buried.