Persistent Slabs
- Alta quota
- Limite del bosco
- Sotto il limite del bosco
- Probabilità
- Very Likely
- Dimensione
- 3
Once triggered, today's avalanches will break deep and wide, taking out the entire seasons snowpack like Saturday's large avalanche near Currant Creek Peak which Andy discusses in the viddy above.
Most slopes have persistent weak layers of faceted snow in the bottom half of the snowpack. New snow that fell in January formed a slab on top of these weak layers. Imagine a building with a weak foundation but we keep adding additional floors on top - eventually the whole structure collapses. New snow and wind drifted snow has added more floors to this unstable structure.
While much of our terrain exhibits weak layers of snow, the slab on top is more variable. The most likely places to trigger a slide are recently wind loaded slopes where the slab is thicker and more cohesive. Recent strong winds have reached below treeline and affected many slopes.
THIS AVALANCHE PROBLEM IS TRICKY - Tracks on a slope do not mean it's safe. As a matter of fact, as the snow gains strength it allows us to get well out onto the slope before it fails and it may be the 2nd, 3rd, or even 10th person on a slope who triggers the slide.
And here's where the rubber hits the road... recent avalanche activity shows us that avalanches are unmanageably large and breaking to the dirt!
I describe this set up in the video below
Photo below from an east facing slope shows that weak, rotten foundation in the snowpack near the ground. All the snow above it is what will avalanche.
