Southern San Juan
AvalancheChris Bilbrey · Mar 13, 2022 · Southern San Juan
Weather
Warm and sunny to start. Clouds started streaming overhead around noon. Southwest wind increased throughout the day with light snow transport along ridgetops and high peaks.
Snowpack
We observed moist grains 5 to 10 cm below the surface resting over dry snow on east to south-facing slopes near and below treeline. Northeast-facing slopes warmed just enough to develop a thin surface crust once shaded in the afternoon. North-facing slopes held soft, dry snow on the surface. We found overall good bonding in the upper snowpack between recent storm layers on northerly-facing slopes near and below treeline, with no discernable weak layers above the 2/21 interface. The 2/21 interface is between 100 and 130 below the surface. Stiff, wind-drifted slabs were unreactive to ski pressure on slopes up to about 35 degrees. The most notable interface we found was in a snowpit on a northeast aspect in the alpine. In that snowpit, we found a thin, semi-reactive layer of facets that formed in early-March sitting below a dense slab (P to 1F) about 80 cm's below the surface. The faceted layer produced planar failures in Compresstion Test but failed to produce propagating failures in Extended Column Test suggesting a stubborn nature at present. No cracking or collapsing observed.
Avalanche
Lots of evidence of Loose Wet avalanche activity from the past two days on east to south through west aspects. Many older avalanches that most likely ran during our last storm cycle or from strong northwest winds post snowfall.