Northern San Juan

Avalanche

Colin Mitchell · Dec 12, 2021 · Northern San Juan

Weather

Warm temperatures for December, right around freezing, and lots of solar radiation. Clear skies in the morning, with a few high, thin clouds moving in around midday. Winds were light below-treeline, but were strong in the alpine and were efficiently loading northerly-facing slopes.

Snowpack

We traveled on south and southeast aspects near and below treeline. The snowpack was almost completely made up of last week's snow. We probed a few areas that had 4-6" of old, crusty snow at the ground, but these spots were isolated. and discontinuous. HS was around 60 cm. The upper 10 cm or so was 4f wind-packed/pressed rounds. Below this were F-hard decomposed/fragmented grains to the ground. The upper layer was sticky and getting moist from the radiation and warm temps, but never got to the point of being wet.

Avalanche

Many avalanches visible on the north-facing side of the gulch. All of these slides appeared to have occurred during or right after the 12/9-12/10 storm. All the chutes that drop off of the ridge heading up towards MacMillan had run D2. All of the alleys in the area known locally as Prospect Trees had avalanched as well. Crowns were sometimes filled in and hard to discern, but large debris piles were hard to miss.