Persistent Slabs
- Hochgebirge
- Waldgrenze
- Unterhalb der Waldgrenze
- Wahrscheinlichkeit
- Very Likely
- Größe
- 2
Persistent weak layers formed in November continue to plague many slopes, and last week's windy storm created a thick slab overlaying the weak layers, which created poor snow structure and an unstable snow situation in many areas.
There's a good chance a person can trigger a slab avalanche on a buried persistent weak layer of facets 1-4 feet deep. Where the snow is deepest like at upper elevations, this layer may be starting to gain some strength, but in areas with shallower snow, like low elevations or places scoured by winds, this widespread layer of loose sugary snow remains weak.
Mark rode throughout Copenhagen Basin Friday and found an unstable layer of surface hoar on top of these facets (video below). He thought he would have easily triggered a slide if he had tried to ride on a steep slope. The party experienced plenty of collapsing.
***Since we don't trust slopes with this kind of buried persistent weak layer, we'll continue to avoid avalanche terrain where it exists by staying off and out from under slopes steeper than 30°.