Persistent Slabs
- Alpine
- Treeline
- Below treeline
- Likelihood
- Possible
- Size
- 2–3
It remains possible to trigger avalanches that break 18 to 30 inches deep on weak snow buried in early December. This threat is most widespread on upper-elevation, shaded slopes. It is isolated on mid-elevation and sunny slopes.
Recent observations have shown some variability in the sensitivity of this layer. No propagation in the Link Lake area Tuesday where the layer was clearly visible, but propagation with relatively small forces further southeast on Saturday. The kicker is that any triggered slide will be very difficult to escape and involve more than enough debris to bury or injure a person. A classic low-likelihood, high-consequences dilemma.
The most straightforward way to manage this lingering hazard is to avoid riding on or below steep, shaded slopes. If you choose to step out, you can reduce the chances and consequences of a nasty surprise by avoiding steep, convex slopes above terrain traps like trees, rocks, and gullies. Slopes with variable snow depths are pockmarked with unidentifiable trigger points. These slopes are often scoured and loaded by cross-slope winds.
(12/21/2024)
The image shows a large avalanche that failed naturally in the central Whitefish Range. This avalanche failed on a north facing slope at upper elevations.