Persistent Slabs
- Alpine
- Treeline
- Below treeline
- Likelihood
- Possible
- Size
- 4
The image above shows the persistent weak layer (PWL) underneath about 2 feet of snow that has been causing most recent avalanches. Despite recent warm weather it hasn't gone away and has only become a little less weak. What this means is that the likelihood of triggering an avalanche on this layer has gone down (thus the danger level has decreased). However the layer remains, and I still don't trust it.
Where does this weak layer exists? It can be found across a wide range of aspects and elevations shown in the aspect/elevation diagram (or "rose") above. The bullseye locations are basically all slopes with dry powder near and slightly below treeline today. Above treeline, this layer is a little more pockety in distribution. The scary part about this situation is that this layer and it's ability to produce avalanches is variable.
How to avoid it? There are two options. (1) Ride south facing slopes where this layer doesn't exists but the riding conditions aren't the best. Or, (2) ride northerly facing slopes with dry powder but avoid being on or under any slope steeper than 30 degrees.
Craig gives an excellent description of current conditions in the video below from his field day in upper Chalk Creek yesterday with Ted.