Persistent Slabs
- Alpine
- Treeline
- Below treeline
- Likelihood
- Likely
- Size
- 3
The widespread persistent weak layer (PWL) can be found on essentially all aspects and at all elevations. Although the PWL is slowly becoming more stubborn to trigger, human-triggered avalanches failing on this PWL remain likely on steep slopes. Avalanches could be triggered while you on the slope, but also underneath or on lower-angled slopes that are adjacent (or next to) steeper slopes. Any avalanche failing on this PWL will be 3-5' deep and well over a hundred feet wide.
Wednesday's storm containing strong winds and well over an inch of water further stressed this PWL. On Thursday, UAC avalanche educator Pat Lambrose and I were joined by a BC 101 avalanche class where we continued to get full propagation with extended column tests failing down in the PWL, confirming the PWL simply needs more time to adjust.
I remain in a mindset of stepping back and continuing to avoid slopes steeper than 30°.