Persistent Slabs
N
NE
E
SE
S
SW
W
NW
- Alta quota
- Limite del bosco
- Sotto il limite del bosco
- Probabilità
- Possible
- Dimensione
- 3
If you’ve been following the forecast, you know the current persistent weak layer (PWL) problem has been around for a while—and it’s not going away for the foreseeable future. Several factors keep buried weak layers, especially the 2/11 layer, on our radar:
- Limited loading: We never received a significant load on top of this layer. Ideally, a weak layer gets buried beneath a large amount of snow and water (SWE). Over time, that weight can help the layer adjust and trend toward dormancy. This hasn’t happened yet.
- Shallow snowpack: The overall snowpack is thinner than normal for this time of year. This creates many potential trigger points in steep, northerly terrain where the snowpack is shallow around rocks and terrain features. These spots are difficult to identify and can feel a bit like a minefield.
- Weak snow still intact: The faceted snow remains dry, loose, and unconsolidated. Despite warmer temperatures, the snowpack has not gone isothermal. On shaded, polar aspects, the structure remains layered and winter-like.
- Hard slabs above weak facets: Strong slabs, two to four feet thick, sit on top of these weak layers. This setup is notoriously unpredictable and often produces little to no warning signs. Historically, with this type of structure, avalanche accidents have occurred well after the last major loading event.
Our approach remains simple: avoid steep slopes facing NW-N-E in this terrain altogether.
