Deep Snow, Wind Slabs, Whumpfs on Donner Ridge

High avalanche danger, challenging weather conditions, deep snow, road closures, and poor driving conditions severely limited the places we could access. We finally made it to Donner Ridge. As expected we encountered deep snow and difficult trail breaking. Once we hit the ridge, blowing snow and strong winds created poor visibility. This lack of visibility combined with the flat light made travel difficult. We had to throw a rope tied to the end of a ski pole out ahead of us to see where the ground was and where the edge of the ridge was.

While traveling along the ridge, we found several small wind-loaded test slopes. Pole probes in these areas showed a more dense soft slab of wind drifted snow resting on top of lighter snow. The cornices along the top of these test slopes broke easily in response to a ski kicks and even a tap with a ski pole in one case. Cornice pieces ranged in size and would usually trigger soft wind slab avalanches between 15 to 25 cm (6 and 10 in) deep on the slopes below the cornices. On one of the most wind loaded test slopes, ski kicks near the top resulted in a cornice piece triggering a small wind slab and also produce deeper cracking. 

Another problem for today was the layer of weak snow just below the old snow surfaces. We found the layer buried under 130 cm (50 in) of new snow on a low angle (16 degree) N facing slope at 7720 ft. by probing with our poles. Once we found this layer we decided to do some snowpit tests to see how it reacted to the new load. After digging through about 80 cm (30 in) of the new snow on our skis, we stepped off our skis to dig the rest of the way. Stepping off our skis triggered a collapse in the weak layer and a large whumpf propagated across the slope. Our snowpit test also yielded an unstable result (PST 35/140 END down 140 cm).