Persistent Slabs
- Alpine
- Treeline
- Below treeline
- Likelihood
- Possible
- Size
- 1.5–2.5
You can trigger a large avalanche where weak layers lurk beneath a thick slab. You may get no warning signs like cracking or collapsing before an avalanche releases, and multiple people could ride a slope before you find a trigger point. The places you are most likely to trigger an avalanche are where the snow is thinner and weaker, around trees and rocks, and on convex rolls. Smooth rounded pillows are signs of slopes where the wind has drifted snow. If you trigger an avalanche in this snow, it may step down three to four feet deep, creating a deadly avalanche. You can find safer riding by carefully assessing south and southwesterly slopes for the presence of a buried weak layer or by riding slopes less than and not connected to terrain steeper than about 30 degrees.