Southern San Juan
AvalancheChris Bilbrey · Dec 27, 2022 · Southern San Juan
Weather
Mild December day with overcast skies. Skies turned ominous in the afternoon. The southerly wind became noticeably stronger around 3 pm and snowfall started shortly thereafter and skies became obscured.
Snowpack
The biggest takeaway from our travels today was how trap-door the snowpack felt on northerly-facing slopes near and below treeline. These conditions appeared much different than our last travels south of the Molas Pass area along the US 550 corridor on the 24th. On most slopes, surface faceting ranged 4 to 6 inches with southerlies harboring a thin crust above near-surface facets. Surface Hoar that developed last weekend was preserved and upright in a lot of near and below treeline areas and laid down only in wind-exposed areas. We even found intact Surface Hoar directly above a hard wind layer on northwest aspects at the treeline. Snowpack test pointed to a more stubborn slab, weak layer combination taking moderate to hard force to initiate failure. Regardless, a weak foundation exists below and is likely to become more reactive during the prolonged period of stormy weather to cap off 2022. Even where the slab above drought facets was shallower and softer, we still observed planar/ propagating failures in tests. Alpine snow surfaces were a mixed-bag of hard wind-stiffened layers next to a softer surface. Probing across open areas in the alpine easily broke to the ground and boot penetration was mostly full depth in our northwest and northeast snowpits.
Avalanche
None observed. We triggered a couple of small facet sluffs on steep headwalls around 40 degrees in steepness. None propagated wider than our skis but could push you somewhere you don't want to go if they travel far. The depth of faceted snow in spots in a worrisome structure to stack a dense storm slab above, especially below the treeline on northerly-facing slopes.