Persistent Slabs
- Alpine
- Treeline
- Below treeline
- Likelihood
- Possible
- Size
- 4
Uinta Avy Pro Extraordinaire, Ted Scroggin knows the range and the snowpack like the back of his hand and says this about our current snowpack structure... "Kind of feels like conditions are moving in the right direction towards stable snow. The weak sugary snow near the ground is getting buried by recent storms and wind and is unreactive in snow pit tests where the snow pack is deep. But in places where it might still be a little thin which can be hard to always know, I not feeling too comfortable getting into steeper terrain on the north facing slopes." Ted was near Gold Hill yesterday and has an excellent trip report found HERE.
Here's the setup-
A persistent weak layer (PWL) of faceted, old, sugary snow near the ground is found mostly in mid and upper elevation terrain facing the north half of the compass. Remember- late December storms stacked up remarkable amounts of dense, heavy, water laden snow, coupled with very strong winds, bringing the weak layer to its tipping point. And while all of the snow since Christmas is a good thing that eventually heals this weak layer, it doesn't happen overnight. In fact, we've been seeing very large, hard slab avalanches breaking on our early season problem child or, in snow-geek-speak... persistent weak layer (PWL). Wednesday's heavy load of snow, water, and wind stressed this layer again, and I'd continue steering clear of any steep, wind drifted slope, especially those that harbor old October snow.
For now what makes this layer dangerous is:
- Once triggered, avalanches may break hundreds of feet wide.
- Avalanches will be 3-5 feet deep.
- It may not be the first person on a slope that triggers A LARGE, DANGEROUS avalanche, it may be the second, third, fourth, etc. who triggers it.
- Seeing tracks on a slope DOES NOT mean it's safe.
Here's the good news - This layer doesn't exist on south facing slopes which have excellent coverage, and soft creamy powder.
