Snake River Core and Palisades

The Snake experienced a significant natural avalanche cycle over the last 48 hours. We observed many large persistent slab and wind slab avalanches in steep wind-loaded/north facing terrain around Mosquito Creek and farther west in the Palisades. See photos below.  Individual events will be added soon. Snowpack info below.

No cracking or collapsing where we traveled.

We dug on a north-facing aspect at 9,200’ to take a closer look at the snowpack structure after the recent storm.

Mid storm weaknesses appear to be gaining strength. No propagation at this interface down 40cm. No shooting cracks, collapses, and a ski penetration of about 2cm support this. Despite the promising evidence, I would still be concerned in steep previously wind-loaded terrain given the BIG load that was just added to the snowpack (~2-2.5” SWE in 36 hours).

We found 2-3.5 feet of snow above the January Drought Layer (JDL). The slab is almost a hard slab in sheltered terrain, but not quite. Mostly four finger hardness with some 1 finger near the JDL interface. Definitely a hard slab above the JDL in higher, windier areas. We found 6-8mm surface hoar at the JDL interface in our pit. This surface hoar was starting to lean with the weight of the overlying slab, but is still mostly upright. No surface hoar was observed at a recent human triggered avalanche that we visited which ran on 1mm facets. Our test pits produced a mix of propagating and non-propagating results.

Our takeaway was that it looks like it’s getting difficult to impact the JDL as a human given the depth at which it is buried and hardness of the overlying slab. The sensitivity of this layer is trending towards stubborn, but the resulting avalanche could be very large if triggered. The recent storm shocked the snowpack and it is still adjusting to the load. Steep terrain that is wind-loaded and/or east through north facing should be given space as this process takes place.