Persistent Slabs
- Hochgebirge
- Waldgrenze
- Unterhalb der Waldgrenze
- Wahrscheinlichkeit
- Possible
- Größe
- 2
The primary avalanche concern is a weak layer of faceted snow from the December dry spell, buried on 12/25, about a foot below the surface on west, north, east, and southeast aspects. While this weak layer is widespread, the overlying slab required to create an avalanche is not.
Near treeline, westerly, northerly, and easterly aspects are the most suspect, where cohesive slabs 1–2 feet deep are more consistent. Terrain transitions are critical: you may move from soft, weak snow or scoured surfaces to standing atop a supportable slab resting on weak facets. Avalanches triggered 1–2 feet deep could potentially step down to basal facets near the ground.
Above treeline, the likelihood of triggering an avalanche is decreasing. Strong northerly winds have stripped snow from many aspects, leaving dirt exposed on some slopes and a stout wind crust capping the weak layer on others. Combined with the early December and basal facets trending toward dormancy, the likelihood of avalanches is actively dropping. However, thin, rocky slopes should still be evaluated carefully. We are actively working to refine the danger rose and identify the most suspect zones. Today, Dave is heading into the alpine to assess conditions and help determine when we can start considering terrain above treeline as low danger.