Persistent Slabs
- Alpine
- Treeline
- Below treeline
- Likelihood
- Possible
- Size
- 1–2
You can trigger an avalanche at upper elevations where a cohesive slab of snow rests on weak layers and crusts buried one to three feet deep. You are most likely to find these problematic layers on northeast through east to south-facing slopes, but the most dangerous slopes face east and southeast. Obvious signs of instability, like cracking and collapsing, may not be present before you trigger a slide. Multiple people can ride a slope before someone finds a weak spot and triggers an avalanche. Look for and avoid slopes with weak layers in the upper snowpack, or stick to slopes less than about 30 degrees as a safer option.
As the sun and warmer temperatures create wet snow on the surface, be wary of snow shedding off steep, rocky slopes. If you notice rollerballs or pinwheels in the surface snow, it’s time to seek colder slopes or simply call it a day.
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