Persistent Slabs
- Alpine
- Treeline
- Below treeline
- Likelihood
- Likely
- Size
- 2
A persistent weak layer of faceted snow that developed during the cold dry period in mid November is now present on aspects that face W-N-SE. A fresh load of 14" of snow may be enough to wake up this PWL and produce avalanche activity today. Audible collapses and shooting cracks are sure signs that the buried weak layer is failing under the weight of the new snow. This condition is most dangerous and wide spread on slopes facing NW-N-E, where wind drifted snow has built thick slabs on top. These hard slabs are 1-4' thick and can produce very large, deep, and potentially deadly avalanches. Fresh wind drifts formed on these slopes again yesterday during the storm. A slide triggered in a fresh drift can step down and trigger one of these larger more dangerous avalanches. Avoid slopes steeper than 30 degrees that face W-N-SE.
The buried weak layer sits right behind my glove in this photo. If you dig down, it is easy to locate because of the brown dust in the layer.