Unstable wind slabs on Lincoln Ridge

We went to Lincoln Ridge today to look at the newly developed wind slabs and to assess weakness in the upper snowpack. We didn't have to travel far along the approach before we were able to see unstable wind slabs and long shooting cracks on road cut test slopes. The newly formed wind slabs were on top of just 1 inch of faceted snow that covered fairly smooth bare ground. Here we were able to intentionally trigger 4 inch thick wind slabs failing on the faceted snow below.

With this in mind we had a good idea of what we were going to encounter in the targeted ridgetop near treeline terrain. As we moved up to the ridgetop and more heavily wind loaded areas we encountered unstable wind slabs around 8 inches thick and building at 11:30 am. Here again were were able to intentionally trigger long shooting cracks, up to about 50 feet long. As we had seen on the approach, these cracks were failing on a 1 to 2 inch thick layer of faceted snow from the Dec 9 snowfall. The wind slabs here were 4F+ hardness failing at the old/new snow interface on F hard near surface facets.

We dug a test pit below the ridgetop in a more sheltered area near the lower limit of today's wind loading and adjacent to our snowpit from Dec 2. Here we got repeatable ECTP results at the old/new snow interface. The older layers of weaker snow below were unreactive with the current new snow load.