Northern San Juan
AvalancheChris Dickson · Dec 6, 2024 · Northern San Juan
Weather
Temperatures were balmy with strong sunshine and no wind.
Snowpack
Most obvious signs of instability have gone quiet. We did not witness any cracking or collapsing as we travelled through a variety of terrain. We dug a snowpit above treeline on an easterly-facing slope and found the new snow faceting above an old wind slab. We did not get any failures in stability tests. And yet (and yet...) we were able to trigger a small persistent slab avalanche below treeline on a repeat-offender steep slope. This just reinforces the "low likelihood, but still possible" paradigm of our current Persistent Slab avalanche problem.
Avalanche
The avalanche we triggered failed on the 11/25 interface, where newer snow sits above very weak facets on a steep shady north-facing slope. The avalanche happened on a steep mine dump, at a convexity, and where the slab was thinner. It was triggered from a hard turn across the top of the convexity, and propagated around 30 feet wide.