Southern San Juan
AvalancheBilbrey Huber FoCAIC · Mar 25, 2021 · Southern San Juan
Weather
Squally weather with periods of S2+ followed by thin clouds and filtered sunshine. During periods of high precipitation, winds were gusty and blowing snow created white-out conditions. Temperatures were in the mid-teen throughout our tour.
Snowpack
We found shallow, non-slabby storm snow below treeline. Snowfall this week has fallen right-side-up and is bonding well to underlying old snow layers. As we approached treeline, winds were effectively drifting the new snow into thicker, stiffer slabs below ridgetops. These were reactive to ski pressure and kicking cornice but still small in size. Places where slabs were failing above a firm, melt-freeze crust traveled farther than on due north aspects. We observed clean, sudden planar failures in Compression Test breaking in a layer of near-surface facets below a 1 cm thick crust. Extended Column Test propagated in the same layer with 25 taps. Although it took moderate to hard force to initiate failure, these test results highlight the looming concern for slides to break deeply with added new snow load.
Avalanche
We triggered several small loose dry sluffs with ease below ridgetops. They quickly traveled around 100 feet down the slope above a crust before coming to rest. Slopes angles were around 35 degrees or slightly less.