Persistent Slabs
- Alpine
- Treeline
- Below treeline
- Likelihood
- Possible
- Size
- 2
The bottom third of the snowpack is all weak, rotten, faceted snow which is the persistent weak layer. A cohesive slab 1-2 feet thick rests on top of this weak layer. This set up is the exact recipe for avalanches, but they have gotten harder to trigger. What's espeically dangerous about this set up is that you don't have to be on a slope to trigger it, just tickling it from the bottom can trigger an avalanche.
This weak snow exists throughout the Uinta Mountains on NW through SE aspects. What is more variable is the slab on top. Places to trigger an avalanche are where the slab is thicker and more cohesive. Slopes receiving even just a little wind-blown snow will have this cohesive slab. Yesterday's strong winds (see discussion below) likely founds some snow to transport and have kept this avalanche problem alive.
This avalanche on Hoyt Peak is almost a week old but shows the type of avalanches we're dealing with. It was 18-24 inches deep and 200 feet wide triggered by a snowmobile low on the slope.
Unfortunately, this avalanche problem will be with us for most of the season. The tricky part now is that slopes with the most snow where we want to ride are ones where this avalanche problem exists. The way to avoid it is by simply avoiding avalanche terrain which means riding slopes less than 30 degrees in steepness.