Persistent Slabs
- Alpine
- Treeline
- Below treeline
- Likelihood
- Possible
- Size
- 3
The snowpack has a weak foundation of persistent weak layers of facets or sugar covered by a hard slab of snow that will be growing in size as more snow is added on top. Many avalanches happened last weekend and more will occur. More snow today and this weekend will add more weight and stress to the snowpack and make conditions become steadily more dangerous through the weekend.
The good news is that the snowpack is slowly getting deeper and approaching 4 feet deep in places. The bad news is that this means avalanches are getting larger and more deadly. There are two main weak layers (1) one is in snow from late November/early December near the ground, and (2) the other is in the middle of the snowpack from a dry period in mid January. In places with a thinner snowpack, these weak layers have merged and it's hard to distinguish them. JG's snowpit below shows these two weak layers well.
THIS AVALANCHE PROBLEM IS TRICKY - Tracks on a slope do not mean it's safe. As the slab on top of the snowpack gets thicker and stronger, 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.