Northern San Juan
AvalancheAmy Pertuz · Jan 20, 2022 · Northern San Juan
Weather
Sunny, beautiful, and cool. 2" of new snow from Wednesday pm in this zone. Light-mod breezes from north were not moving any snow
Snowpack
Southerly aspects in this drainage have an HS ranging from 60-160cm in the upper BTL elevation band. Upper elevation southerly aspects are burned off on ridges, but prior wind-deposit from northerly winds put enough snow into high S and especially SE facing lee features that decent coverage remains near and above treeline on this aspect. On a S aspect at 10,800', two melt-freeze crusts were found in the upper 10cm of the snowpack. The upper ~1cm crust, topped by 4cm of new snow, was quite soft, and could barely be picked up in a chunk. A very soft layer of near-surface faceted grains about 2cm thick sits under this crust, and this sits atop of a much stouter 1cm thick melt freeze crust. The bottom margin of this lower crust has a thin layer of very weak faceted grains (4F-) next to it. This lower crust/facet combo sits atop a 30cm thick slab of recent storm snows which have faceted out (4F>1F-), and this 30cm layer rests on a hard interface with a 1F+ midpack slab. HS in this location was 166cm. On the surface, this upper snowpack is not an issue, and only minor cracking of this upper crust layer was happening around my skis. If this double-crust-facet-sandwich received much of a load on top, though, it has problematic structure which would likely produce propagating failures. On a nearby SW aspect at 10,800' the surface crust was stouter, though dry snow from Wednesday night lingered on the surface. Large percolation columns were found on this aspect in the top 10cm of the snowpack. These appeared to flow into a stout crust 10cm below the surface. HS here was 135cm. Ski penetration varies considerably even across small distances on W, S and E aspects, from 20cm to 0cm in just a few meters
Avalanche
No recent avalanches.