Persistent Slabs
- Hochgebirge
- Waldgrenze
- Unterhalb der Waldgrenze
- Wahrscheinlichkeit
- Likely
- Größe
- 3
A buried persistent weak layer of faceted snow exists on most aspects. This layer is buried roughly two feet below the surface and is easily found with your shovel. Outward signs of instability like collapsing and cracking are no longer obvious. The odds of triggering an avalanche have dropped, but the consequences remain the same. These weak layers can still produce deep and dangerous slab avalanches. You are most likely to trigger an avalanche in areas with a thin snowpack, like slopes that were heavily scoured by winds before the January storms laid down a slab. Slopes that have previously avalanched are also suspect. Any steep, thin, rocky area is a likely trigger point.
If you choose to step into avalanche terrain, stack the odds in your favor by choosing terrain with clean run outs. Choose terrain that gradually transitions back to lower angles and avoid steep slopes that end abruptly in gullies or terrain traps. Avoid skiing above cliff bands or stands of trees that you could be raked through. Think about the shape of the terrain and where you would go if an avalanche occurs. Remember at Moderate danger, human-triggered avalanches remain possible.
This profile is from a NE facing slope at 11,250'. The top few inches are soft snow that fell over the past week. The 4 finger to 1 finger slab is the rest of the snow that fell in January. The December drought layer is becoming more dense, and did not produce a failure. The 4 finger facet layer beneath is also gaining strength. The weakest snow remains near the ground where fist density facets can be found. An extended column test produced results of ECTP 30 at the top of this layer. What this tells us is that in deeper snowpack areas, it is becoming harder for the weight of a person to affect buried weak layers, but if they did, the avalanche would be deep and nearly to the ground. In shallower snowpack areas, it is easier to affect this buried weak layer, and human triggered avalanches are much more likely.
