Persistent Slabs
- Hochgebirge
- Waldgrenze
- Unterhalb der Waldgrenze
- Wahrscheinlichkeit
- Likely
- Größe
- 2–3
Our snowpack is plagued by two prominent persistent weak layers:
- Facets and isolated surface hoar buried 1-2' down: The train of storms that brought significant snowfall across our region buried a weak layer that has produced avalanche activity in all of our zones, including the large avalanche pictured at right. On Wednesday, in the Hyndman Creek drainage, I triggered a very large, likey unsurvivable avalanche that failed on one of these weak layers and then stepped down to weak snow near the ground (described below). Thanks to the nature of these layers and the ongoing wind-loading, triggering an avalanche on these layers is likely today. These layers are probably the culprit weak layers in some of the recent avalanches described in the wind slab section below.
- December facets, now buried 3-4' down: As this layer becomes more deeply buried it becomes harder to impact. Obvious signs of instability (like collapsing of the snowpack) become less frequent, the first sign of instability may be a very large, destructive avalanche like the one I triggered on Wednesday. Unfortunately, this layer has shown few signs of healing. Thanks to the thick slab on top,this layer is trending towards a deep persistent slab problem: difficult to trigger with terrible consequences if you do.
We are in the midst of a multi-day wind event that is producing strong W to NW winds. These winds are loading many slopes at middle and upper elevations, keeping these weak layers on edge. Avoiding slopes over 35 degrees that have been affected by the wind will greatly reduce your chances of triggering a persistent slab avalanche. Keep in mind that these slides can be triggered remotely—from below, above, and to the sides of steeper terrain.
(2/3/2021) This large slide likely occurred sometime Tuesday night (2/2) or Wednesday morning (2/3). It released on a 7,700' E-facing slope in Croy Canyon above Democrat Gulch.