Persistent Slabs
- Alpine
- Treeline
- Below treeline
- Likelihood
- Possible
- Size
- 4
Throughout the Uinta Mountains, there is a slab 2-5 feet thick resting on a persistent weak layer (PWL) of facets about a foot above the ground. This PWL exists on most slopes except ones facing due south and southwest.
It's a tricky situation because it is low probability/high consequence. What we know is that if we trigger a slide, it can be 2-5 feet deep and hundreds or thousands of feet wide and deadly. Unfortunately, we don't know the exact probability of triggering an avalanche on this weak layer but it has gone down since snowfall about a week and a half ago. Today's snowfall may only raise the probability a small amount since it is only a few inches of light snow.
Another reason it is a tricky situation is that with such a supportable slab on top of this weak layer, a slope may have many sets of tracks on it and still slide if someone hits a thin spot in the snowpack. You can guess where those thin spots are but you never really know becuase they can be near a rock hidden under the snow.
What to do? Unfortunately it's just a season with a dangerous snowpack. There's no way around that fact, and I would avoid all big, open slopes steeper than 30 degrees. Slopes above treeline, especially with recent wind drifted snow, will be the most dangerous. Triggering a slide on slopes near treeline remains possible.
