Professional Observation

Observation Details

Signs of Unstable Snow

2 spooky localized collapses in the flats at 9350 feet where the persistent weak layer was down 20 cm below the surface and all the snow above it was wet.

Key Points

I traveled on north, east, and southeast aspects to 9800 feet in Bishop Creek to look at what warming was doing to the snowpack and think about what it might do to the persistent slab problem as temps soar over the weekend.

• Almost every aspect I traveled on below 9400 feet had wet melt-freeze snow at the surface. I stomped on some steeper east and southeast-facing test slopes in the heat of the day and only got small rollerballs, so I would call the loose wet avalanche problem “stubborn.”
• Above 9400 feet solar aspects and low-angle northerly slopes were also wet or crusted over. The presence of a surface crust on northerlies was variable depending on slight changes to aspect and slope angle.
• I dug for the persistent slab problem on a northeast aspect at 9800 feet where the whole snowpack was dry. I got non-propagating results in my tests. Notably, at this location, the crust under the weak layer was not very pronounced. (See profile) I stopped just around the corner on a steeper, east aspect where the surface had been wet and was refreezing. There I got propagation on the same weak layer (ECTP22, see pit photo). The crust below the weak layer in my second pit was thicker and harder. The top 15 cm of the snowpack in this location were moist to wet. In both locations the weak layer and the snow directly above it were dry. The 2nd snow pit and my collapses, where the snowpack was wet down to the buried crust, make me think that wet slab avalanches will be possible once temperatures climb enough that the snowpack is wet down to the persistent weak layer.