Persistent Slabs
- Alpine
- Treeline
- Below treeline
- Likelihood
- Unlikely
- Size
- 1–2
An extreme wind event last week formed a few thin, hard slabs scattered across all elevations, in concave catchments and behind abrupt transitions in the terrain. Where these drifts formed over facets on colder aspects, you might still be able to trigger one, and they're stiff enough to knock you off your feet. Look for firm, rounded snow surfaces to identify potential features of concern.
Snowfall and wind drifting in early December formed slabs up to a few feet thick over facets near the ground. These weak layers are most widespread on the northern half of the compass, and slabs are most common at mid and upper elevations. Mild weather through the middle of December has helped the snowpack adjust to its current load, or in some cases, the slabs have decayed away. The last documented avalanche on these old, weak layers was accidentally triggered on 12/14.
An example of a thin, hard slab over sugary facets. The resulting avalanche would be small in size, but the hard snow surface could easily pull you off your feet or push you into a tree.