Persistent Slabs
- Alpine
- Treeline
- Below treeline
- Likelihood
- Possible
- Size
- 1.5–3
Storm snow has consolidated into a supportable and cohesive slab over weak layers and cursts. Slab thickness will vary by elevation and from one end of the range to the other, but the common thread is that a significant load has been added to our snowpack since the end of January.
Persistent slab problems are difficult to manage and challenge our patience. Shooting cracks and collapses are clear warning signs of the problem. However, feedback is often irregular or non-existent. This means that triggering a large avalanche may be the first sign that a slope is unstable. Avalanches may be triggered remotely—from flatter terrain below or adjacent to steep slopes. Persistent slabs, such as storm or wind slabs, often propagate widely and beyond terrain features that may limit surface instabilities. The best option is to minimize your exposure to steep terrain and large avalanche paths. Use extra caution in rocky, complex terrain, unsupported slopes with shallow trigger points and convex rollovers, and slopes with inconsistent snow depth. When in doubt, give yourself a wide safety margin, be wary of hazard that may reside above you, and use terrain choice to limit your exposure.
(2/5/2025)
Large remotely triggered persistent slab avalanche near Virginia Lakes on 2/5/25.