Southern San Juan
AvalancheChris Bilbrey · Jan 31, 2023 · Southern San Juan
Weather
Light snowfall and southwest winds throughout the day. Skies were obscured.
Snowpack
New snow totals ranged 4 to 6 inches below 10,000 feet, 7 to 9 inches near 11,000 feet, and a foot plus above the treeline. The storm snow was 4F for about 2 inches above the new/ old interface and softened to 4F-/ F hard closer to the surface, and was bonding well to the variety of old surfaces (decomposing fragments/ near-surface facets on northerlies, a crust on east to south, and wind-board/ sun crust on exposed alpine slopes). We encountered a very soft slab forming near and above the treeline. These fresh slabs/ deeper drifts were reluctant to move on steep test slopes or produce clean failures in snowpack tests. Near-surface facets buried around one to two feet deep were rounding and mostly contributed to resistant planar or break failures in Compression Tests. The most preserved faceted snow layer we found in multiple pits sits below a P- hard crust or a stout 2-inch wind-board directly below the new snow. Storm snow above lacks the volume necessary or is too soft to propagate a failure in Extended Column Tests. However, deeper/ stiffer drifts may exist below ridges that could be more likely to fail from the added weight of a rider. Weak snow layers from November are mostly out of range (too deep) of rider-triggering and sit below a thick, consolidated mid-pack slab on most aspects and elevations. These looming grains near the ground likely need a significant snow load to become reactive again but could yield very large avalanches during a prolonged multi-day storm event.
Avalanche
No new avalanche activity, although visibility was poor.