Persistent Slabs
- Hochgebirge
- Waldgrenze
- Unterhalb der Waldgrenze
- Wahrscheinlichkeit
- Likely
- Größe
- 3
Persistent Weak Layers (PWL) are defined as follows: This avalanche problem is related to persistent weak layers buried in the snowpack. Release a cohesive layer of soft to hard snow (a slab) in the snowpack when the bond to an underlying layer fails and releases an avalanche. These weak layers typically include buried surface hoar, depth hoar, and faceted crystals.
In simple terms - we have buried weak faceted snow with a stronger, more dense layer of snow on top (this creates the problem). If you decide to ride slopes greater than 30° degrees in steepness (avalanche terrain), you are messing with a very dangerous avalanche problem. Below are a few things to keep in mind when dealing with a PWL.
- Responsible for roughly 70% of all avalanche fatalities
- Avalanches can be triggered from a distance.
- Can be triggered days, weeks, or months after being buried
- Tracks are not a sign of stability, and you can still trigger the avalanche even though the slope is tracked up.
Travel Advice: Avoid steep west to north to east facing terrain above 8800'. Dangerous avalanche conditions still exist at mid-elevations, as we are still seeing avalanche activity in the upper reaches of the mid-elevation band. Steep terrain means any slope that is greater than 30° in steepness. Make sure nothing is steep above or adjacent to you as you travel as avalanches can be triggered from a distance. Personally, I am not messing with this terrain at all. I will be riding or walking in low angle terrain for the foreseeable future.
Below Greg talks about the conditions he saw traveling along the Park City Ridgeline yesterday.