Persistent Slabs
- Alpine
- Treeline
- Below treeline
- Likelihood
- Possible
- Size
- 2
A persistent weak layer (PWL) of October and November facets makes up the base of the snowpack on west-north-east facing slopes at the mid and upper elevations. In these areas, it is still possible to trigger an avalanche up to about 2 feet deep and over 100 feet wide.
This setup was obvious over the weekend, with widespread avalanche activity and plenty of red flags. As we move farther from the loading event, those signs may be less obvious, but the structure has not changed. Sensitivity and overall likelihood are slowly dropping, but the consequences remain high. Cracking and collapsing of this weak layer was noted in the upper Cottonwoods as recently as yesterday.
Pull out your shovel and the poor snowpack structure is obvious. Note the consolidated slab over the 'rock salt' facets at the base of the snowpack.