Persistent Slabs
- Alpine
- Treeline
- Below treeline
- Likelihood
- Possible
- Size
- 2.5–3
Persistent weak layers buried in the lower half of the snowpack have been quiet for the past few days, but they are probably not done just yet. The biggest new snow load so far this season is forecast to be placed on top of the snowpack over the next 60 hours. It might take until this evening or later for these deeper weak layers to wake back up, but when they do expect large, destructive avalanches to occur.
Snowpack collapse, deep cracking, and whumpfing will be indications that these deeper weak layers are becoming reactive again. There is certainly a chance that a large avalanche could occur without these obvious signs of instability showing first.
Move through terrain with the mindset that triggering is most likely to occur somewhere where the overlying slab is thin such as around the edges of wind loaded areas or near rocks that bring the weak layer closer to the snow surface. A slope that avalanches today could easily have previous tracks on it. Keep your margins of safety as wide as possible and consider reducing your exposure to avalanche terrain as the day progresses. Anticipate that an avalanche will break wider and run further downslope than is common for the terrain you are in.
(1/15/2024)
Large natural avalanche between Lincoln and Anderson Peak-thought to have occurred on Sat Jan 13. See the size of the crown relative to the people.
