Persistent Slabs
- Alpine
- Treeline
- Below treeline
- Likelihood
- Likely
- Size
- 4
There is a persistent weak layer of faceted, old, rotten snow near the ground mostly on north-facing slopes. Very large, hard slab avalanches have been breaking on this layer. Wednesday's heavy load of snow has stressed this layer again, and I wouldn't trust any slope facing north. At upper elevations, even west and southeast facing slopes may have this layer that can produce avalanches.
All of the snow since Christmas has been a good thing that will heal this weak layer, HOWEVER, it doesn't heal overnight. For now what makes this layer dangerous is:
- Once triggered, avalanches may break hundreds of feet wide.
- Avalanches will be 3-5 feet deep.
- It may not be the first person on a slope that triggers A LARGE, DANGEROUS avalanche, it may be the second, third, fourth, etc. who triggers it.
- Seeing tracks on a slope DOES NOT mean it's safe.
Here's the good news - This layer doesn't exist on south facing slopes which have excellent coverage, and soft creamy powder.
Photo - Northeast facing slope at 9600 feet showing the weak snow near the ground which looks sugary and granular.
Photo - An example of the snowpack on an east facing slope that doesn't have the weak layer. The snowpack is just strong and right-side-up, meaning it's hard at the ground and gets softer near the top. Low elevation east facing slopes generally don't have the weak layer however we have been finding it on east aspects as you gain elevation.