Persistent Slabs
- Alpine
- Treeline
- Below treeline
- Likelihood
- Possible
- Size
- 1–2
The persistent slab problem remains, well, persistent. This problem is two-fold. Weak, sugary snow on many aspects exists at the bottom of the snowpack left over from a cold and dry November. There are also hard (up to pencil-hard) wind slabs deposited from strong winds. The December snow sits on top of everything and has settled into a firm, cohesive slab. Recent mild temperatures have expedited the settling process, giving the slab more cohesion and a higher propensity to propagate when triggered. The problem will most likely be found in steep, northerly terrain where the wind has built slabs and added additional stress on top of the weak basal facets. Two natural wind slab avalanches were observed in steep northeasterly terrain yesterday, most likely failing on the interface between the old and new snow.
You may see signs of instability as you travel, such as whumfing or cracking. You may also not see any red flags until the avalanche is triggered from on, above or below the slope you want to ride. Continue seeking low-angle (less than 30°) terrain and watch out for terrain traps where even a small avalanche can bury you.
Natural wind slab. 10,200 NE aspect
Photo: Alex Drinkard