Southern San Juan
AvalancheGrady James · Dec 29, 2020 · Southern San Juan
Weather
Skies were clearing as we began our tour, with most of the cloud bank below us in the Animas valley. At 1400hrs views of Purgatory were obscured but had cleared by 1600hrs. BTL winds were calm.
Snowpack
11,200' HS was 120-150cm on N-NE aspects in well spaced old growth stands. HST was right at a Cubit. Thats 45cm or 18" for those that do not use biblical units of measurement (ask Doug Krause). CT9 RP, and ECTN12 down 45cm on storm interface. ECTP26 down 74cm on Dec11 interface. Ski and skin travel was easy to feel the upside down storm snow under foot. Collapses were abundant and often propagated large distances.
Avalanche
Many instances of natural failures towards the end of the storm. Some resulted in very widespread cracking on slopes 25-40 degrees but the slab supported itself after failing in tension. These instances looked to be deeper than the storm slab interface.. Had a few obs of natural activity that were able to run. Crown size and debris indicate it was confined to the storm snow near or on the interface. 20201228pm N, 11,000': SS-N-R1-D1-I 20201228pm SSW, 10,700': SS-N-R1.5-D1.5-I 20201228pm E, 11,000': SS-N-R2-D1-I