Storm Slabs
- Alpine
- Treeline
- Below treeline
- Likelihood
- Likely
- Size
- 1.5–3
1 to 3 feet of storm snow fell during the Wednesday/Thursday storm with 6 to 12 inches of snow forecasted for today. A layer of graupel exists below this recent storm snow on a firm melt freeze crust. Some of the avalanches that occurred yesterday failed on this graupel/crust combo, especially in wind loaded areas that had a cohesive slab. There is also the possibility that other weaknesses exist around this old snow surface crust, with reported whumping sounds and collapses yesterday.
Avalanches could occur in wind loaded or wind protected areas across all aspects and elevations. The low density storm snow lacked slab characteristics in some areas yesterday. Where slabs of wind blown snow have formed below ridges, in gully features, and in open areas- cohesive wind slabs could fail down to the old snow/new snow interface. Slab thickness could be 2 to 5 feet deep resulting in large to very large avalanches. In wind protected areas, additional storm slab weakness is expected today. Failures could occur at the interface from today's snowfall, or within the new snow where weaknesses occur. These could result in storm slabs or hybrid dry loose sluffing that runs fast and long distances similar to avalanches reported yesterday.
Recent avalanches, snow surface cracking, or snowpack test failures will indicate unstable snow in your area. Traveling on slopes that are under 30 degrees in steepness with no steeper connected terrain near or above will be the easiest way to avoid this avalanche problem. Today will be stormy and windy again with periods of poor visibility. Plan routes to avoid you and your group's exposure to this avalanche problem.
(3/13/2025)
A wide propagating human triggered D2 storm slab on a SE aspect. Skier in the track of the avalanche with the crown in the background.
Perry's Peak, Donner Summit area.