Northern San Juan
AvalancheChris Bilbrey Mike Barney · Jan 26, 2021 · Northern San Juan
Weather
Cold and calm with overcast skies. Light snow that maybe added up to a inch throughout the day.
Snowpack
We found around 45 cm of new snow since January 22 at treeline. Remarkably, our recent storm event came and went with little to no wind affect or drifting with lots of snow remaining in the treetops at 11,800 feet. In our snowpit on a northeast aspect near treeline, we did observe propagating results in Extended Column Test with moderate force failing below our recent storm snow - 47 cm down from the surface. We did not observe failures in facets that formed in early December. Outside of these test results, no other signs of instability while traveling along ridge tops and on north and east aspects near treeline. Once we descended an east-southeast aspect into the below treeline elevation, signs of unstable snow increased. We remotely triggered a small soft slab avalanches on a southeast-facing slope from around 150 feet away along with long-running surface cracks. Poking into the snow at one of the cracks, we found 1 cm of near surface facets sitting above a crust that was likely buried on January 19 and now under about 35 cm's of snow. We also observed a large rumbling collapse and en echelon cracks while walking along the edge of a west aspect below treeline. Cracking there propagated up into terrain with slope angles less than 30 degrees.
Avalanche
We remotely triggered an avalanche below treeline from up to 150 feet away on a southeast aspect. Slopes 35 degrees slid while slopes less steep collapsed, propagated and stayed put. We only observed avalanches below treeline but vis was poor and we only traveled up to the near treeline elevation band.