Southern San Juan
SnowpackChris Bilbrey · Jan 16, 2024 · Southern San Juan
Weather
Sunny, cold day. Moderate westerly wind in the morning relaxed around 10 AM reducing wind loading at upper elevations.
Snowpack
The Gremlins in the basement are not happy with the significant snow load that accumulated over the past 10 days. The majority of avalanches that ran at the tail-end of the stormy period broke in a very weak layer of faceted grains (4F-), 1 to 2 mm in size, and around 60 to 70 cm deep. These grains formed during the prolonged dry spell around the New Year. Before that, the snowpack in this portion of the South San Juans was atypically shallow compared to adjacent areas. The January slab that formed above is primarily F to 4F to 1F, and supportive to skis. Once we stepped off our boards, we easily punched into weak snow layers near the ground. We dug a snow profile on a north-facing slope about 100 feet below one of many crowns. Extended Column Test produced propagating failures with 15 taps on the same interface. Shovel shears identified two persistent weak layers of concern, but each test bypassed the upper layer and broke in the deeper, weaker one. Below the primary failure interface, the snowpack consist of larger, faceted grains of varying hardness - mostly 1F- to 4F, 2 to 5 mm in size, and 30 to 40 cm thick. Despite the weak basal structure, none of the slides we saw gouged to the ground. Throughout our travels, we lost track of the number of rumbling collapses. We also observed extensive cracking across adjacent gullies and terrain features on all aspects, and on slopes as low as 30 degrees. We even observed collapses on slopes that cracked naturally during the storm, but did not slide.