Persistent Slabs
- Alpine
- Treeline
- Below treeline
- Likelihood
- Possible
- Size
- 2–3
You can trigger an avalanche on steep slopes where cohesive slabs sit above weaker snow. The most dangerous slopes are at upper elevations where winds drifted snow into deeper cohesive slabs. Avoid trigger points on rocky slopes at where variable snow depths mean buried weak layers could be closer to the surface. You may not observe any obvious signs of instability, such as cracking or collapsing, before triggering a dangerous avalanche. Watch for small loose avalanches in the afternoon where you find wet snow.
On February 20 and 22, backcountry snowboarders were caught and killed in avalanches in separate incidents. One west of the town of Silverton on a terrain feature locally known as The Nose. The other was near the summit of Berthoud Pass in a terrain feature locally known as The Fingers. In both fatal accidents, the avalanches broke several feet deep and spread wide across multiple terrain features. You can read the preliminary accident reports here and here.