Wet Snow and Loose Wet Avalanches on Andesite Peak

Driving up to Donner Summit the rain switched over to snow at around 7000 ft. We knew to expect wet heavy snow and some wet snow instabilities before we even left the car. When we started skinning, we found 3 to 5 inches of new heavy snow sitting on top of a thicker layer of rain-soaked wet snow. We could see partially covered rain runnels on the snow surface as we moved up through the meadows and low angle slopes indicating previous rain on snow. Quick hand pits showed us that the new snow was not well bonded to the wet snow below it and that there was not much cohesion in the wet snow.

At the mid to upper elevations, we found some small steep test slopes. Ski kicks on these small slopes triggered ski width wide loose wet avalanches on slopes steeper than 35 degrees. These entrained the new snow and a little bit of the older wet snow. If they had occurred on larger slopes, they could have involved enough snow to twist a knee or maybe bury someone. We decided that we were better off avoiding any larger steep slopes. We also found very large cornices hanging over the edges of the steeper slopes near the summit of Andesite. We looked at those from afar but we did not approach them or try to experiment on them.

On the way back down we were able to place a ski cut above a steep section of a larger slope and push some snow into that steeper section of the slope. Once it hit that steeper section of the slope, a ski width wide loose wet avalanche resulted. It traveled 200 ft to the bottom of the larger slope and was about 30 to 40 ft wide by the time it reached the bottom. By the bottom, it looked like there was enough snow moving to at least injure a person and maybe bury someone (size D2). This confirmed our decision to stick to low angle slopes.We continued down on slopes less than 30 degrees in steepness.