Snowpack Collapse on Tamarack South Face

With the avalanche advisory and known probelmatic layer in mind, we decided to go out for a morning tour on the low-angle south face of Tamarack Peak, approaching from the meadow. Once we got above about the Forest Service road (about 9000 ft elevation), we started to hear and feel incredible snowpack collapse. Whumphing was generally heard at our feet and the sound would propogate out about 50-100 meters in all directions. Snowpack collapse was also felt. We experienced this several times on the approach, and eventually snowpack collapse became so consistent that we didn't feel comfortable summiting Tamarack. There was plenty of wind deposited snow and wind pillows throughout the area, but this did not seem to impact the ocurrence or frequency of collapse. On the ski down, the snowpack was collapsing without making any turns.

Our test pit indicated that the probelmatic faceted layer was surprisingly thick in this location, about 40 cm. The faceting process in the old layer had gone clear through to the ground. Being at a relatively high elevation, it makes sense that this old snow had lingered and degraded for such a long time without melting out. In general, it seemed that wind-protected areas with ample exposure to the sky had the weakest snowpack. However, it was clear that this weak layer was probably present anywhere that there was preexisting snow before the storm.