Persistent Slabs
- Alpine
- Treeline
- Below treeline
- Likelihood
- Possible
- Size
- 1–2
You can trigger slabs 1 to 2 feet thick that fail on a layer of faceted snow. This avalanche problem has become more stubborn to trigger and is showing fewer obvious signs of instability after the last week of mild weather. Northerly facing aspects with slope angles near or above 35 degrees pose the greatest risk. Persistent slab avalanches can break above you, propagate surprisingly wide, or even be remotely triggered from an adjacent slope. The last human-triggered persistent slab avalanches occurred on February 28th, here and here. While 2 natural slab avalanches released around March 2nd, here. If uncertainty about the avalanche conditions arises, head to lower angled slopes and less complex terrain.
This photo from Cement Creek illustrates how persistent slabs can be triggered from a long ways away from the start zone. The avalanche was remotely triggered by a snowmobile on 2/27.