Northern San Juan
AvalancheBen Pritchett and Rich Rogers · Jan 4, 2025 · Northern San Juan
Weather
High thin clouds this morning gave way to lowering cloud ceilings and light snow and moderate winds by midafternoon.
Snowpack
The dangerous wind-drifted slopes stood out on the landscape. We could see the feature we hoped to test from 20 miles away. Once at that feature, the drifts we encountered were 1-finger hard and 1 to 4 feet deep, resting on the December drought layer, made up of large-grained Depth Hoar. We triggered collapses in every distinct pocket of wind-affected snow once we left the forest - cracking and collapsing are a sure bet, as are avalanches where the slabs lie on steep slopes. In a wind-sheltered spot near the top of the forest, around 11,600' we measured 4.4 inches of total snow water equivalent (swe) in the snowpack. 1 inch of that swe fell since Christmas Day. 1.3 inches of swe fell during the Thanksgiving storm, and the remainder came from the early season storms. This is more snow than the Cochetopa Pass and Upper Rio Grand snotels (3" swe at each), and similar to the Sargents Mesa (5") and Moon Pass(4") snotels, and less than Slumgullion Pass and Wager Gulch (7" at both). Below treeline there is not enough of a slab to be a problem yet, but the setup is pretty bad. A soft 6 inch thick layer of 4-finger decomposing fragements sits on the Fist minus drought layer. Isolating snowpack tests is nearly impossible as the drought layer falls out of the profile. Near treeline we got an ECTP1 just as got out of the forest into an open slope. From there on it was all cracking and avalanches, until you hit the vast sea of bare ground.
Avalanche
We intentionally remote triggered two avalanches from low-angle ground connected to steep wind-drifted slopes below. One broke around 1 to 2 feet deep (D1.5) and the other broke up to 2 to 4 feet deep (D2).