Persistent Slabs
- Alpine
- Treeline
- Below treeline
- Likelihood
- Unlikely
- Size
- 3
Heightened avalanche conditions exist on upper elevation slopes today, and people could trigger avalanches of previously wind drifted snow failing on a sugary persistent weak layer from last week. Sustained and strong west winds Thursday and Friday moved tons of heavy snow into deep drifts on the lee sides of the major ridges and avalanche starting zones. The fresh drifts were quite sensitive when they first formed, and people easily and remote triggered soft slab avalanches. Natural avalanches occurred on many drifted slopes Thursday night and Friday. The drifts gained significant stability over the weekend, and will be fairly hard and stubborn today. Hard wind drifts sometimes allow people to get out on them before releasing, kind of like a mouse trap.
- Watch for and avoid old drifts near ridge lines and in and around terrain features like cliff bands, scoops, gully walls, and sub-ridges.
- Avoid ridge top cornices, which can break much further back than expected and start avalanches on slopes below.