Southern San Juan
AvalancheChris Bilbrey · Dec 20, 2023 · Southern San Juan
Weather
Overcast skies in the morning. Cloud deck started lowering around 11 AM. Light snow (S-1) started around 11:30 AM, and varying snowfall rates continued throughout the day with only a trace to half-inch accumulation. Winds were light out of the southwest, and an occasional moderate gusts.
Snowpack
Warm, quiet weather over the last 7 days has provided the most positive influence on the snowpack below treeline. Basal layers are getting compressed and becoming harder as the overlying slab settles and stiffens. Probing across below treeline slopes, layering felt fairly homogenous. Despite the slab, weak layer combination taking more loading steps to fail, the shallow nature of those grains should not be discounted. Plenty of mid and upper snowpack weaknesses are emerging and will become a sensitive problem with the next load. Above about 11,000 feet, we observed deeper near-surface faceting, and basal layers are more preserved (larger and more angular). The near treeline band can be thought of as the Goldilocks zone where depths are not as deep as above treeline, and recent warm temperatures do not appear to have had the same strengthening affects as lower elevations. West-facing slopes near and above treeline harbor by far the shallowest and weakest snow structure. Slopes on the east side of north at similar elevations harbor a deeper, more stubborn slab above basal weak layers. Above treeline, we found more height of snow variability. This is having a noticeable affect to overall snowpack structure. Places where the overlying slab is thinner, or scouring is more widespread, the pile of faceted snow at the ground is deeper and propagating Extended Columns tests slid off the weak layer with ease. Wind-drifted alpine slopes in general have harder layering above the basal facets/ depth hoar, but this did not prevent failures in stability test (ECTP 20). Throughout our travels and regardless of total snow depth, boot penetration is mostly to the ground. Our alpine snowpit was the only spot where we didn't punch to the ground when stepping off our boards.
Avalanche
None observed