Southern San Juan

Avalanche

Chris Bilbrey · Jan 23, 2024 · Southern San Juan

Weather

Mild, humid, and mostly overcast day with very light snowfall. No measurable accumulations. Light wind with an occasional stronger puff of air. A few pokes of sun in the morning made the surface snow sticky in spots.

Snowpack

Under the influence of mild weather and no significant snow load, January snowfall is settling into a stiffer slab. This is resting above weaker, faceted snow that got buried around January 4. These persistent grains are the primary weak layer of concern at present. Through visual inspection, we noted these grains were a mixture of rounded and angular edges. This interface is around 80 cm deep below treeline, and just shy of a meter deep near treeline. The layer was 4F hard in our northerly snowpit below treeline and 1F- in our easterly snowpit near treeline. Compression Tests (CT) and Extended Column Tests (ECT) in our below treeline location produced planar, cash-drawer results - CT 15 (SP) and ECTP 26. Tests in our near treeline location were more stubborn to fail, and produced sudden collapse results in CTs with 25 and 26 taps. At upper elevations, the stiffness and weight of the overlying slab is helping compress weaker snow below making is less susceptible to fail. The catch 22 is shallow places still exists across the landscape where it is easier to impact weaker snow below. The same overlying slab also extends well out into more open areas keeping the potential avalanche size large. Places where the overlying slab is shallower, we must assume the same persistent weak grains are not as hard and offer better odds to fail from added weight.

Avalanche

Several small, non-consequential loose snow sluffs on south and southwest-facing slopes above treeline in the last couple of days. These likely ran once the sun softened the snow surface above a melt-freeze crust.