Persistent Slabs
- Alpine
- Treeline
- Below treeline
- Likelihood
- Possible
- Size
- 1.5–3
Weak facets and buried surface hoar sit below a 2 to 3 foot deep hard slab. The likelihood of triggering a slide that breaks on this layer has been decreasing daily, but it is still possible and the consequences are still serious. Shaded slopes steeper than 35° degree, above 8,000 feet and below the exposed alpine is where you could encounter this problem. Avalanches failing on this layer are difficult to trigger and signs of instability will likely not be present. Be diligent with your terrain assessment and wary of steep slopes where this weak layer exists.
Take a look at this persistent slab avalanche triggered two days ago in Prater Canyon in the Salt River Range. While not in this forecast zone, a very similar snow setup exists and this avalanche is a good reminder that these avalanches can still be triggered.
(3/8/2026) Prater Canyon - North 8300’ (X=Snowmobile)
This avalanche was triggered yesterday from the bottom of this sheltered, convex slope which had a skin and ski tracks on it. The avalanche partially buried three riders, one to the chest. A thick ice crust was on the snow surface.