Northern San Juan
SnowpackChris Bilbrey · Jan 7, 2023 · Northern San Juan
Weather
Temperatures were brisk to start but moderated into the mid-20s under sunny skies and a light ridgetop breeze.
Snowpack
We found around 4 inches of new snow from Friday's quick storm. Snowfall, since the holiday storm ended, is mostly 4F to F and this sits above a stout mid-pack slab ranging from 1F to P hardness. Persistent Weak Layers (PWLs) that have accounted for the majority of avalanche activity this season are now buried under a meter or more of snow at the bottom of the snowpack. On north and northeast-facing slopes near the treeline, PWLs were up to 150 cm deep. Warmer temperatures and sunshine have promoted settlement of the holiday slab and this is evident by the limited ski and boot penetration. In contrast to our last visit 3 weeks ago, we observed no cracking or audible collapses through all elevation bands. A buried faceted crust interface on a southeast-facing slope produced more concerning test results than the drought facets on northerly-facing slopes at the same elevation. Storm and subtle density changes in the top 60 cm of recent snowfall produced resistant planar results on multiple aspects and non-propagating results in the Extended Column Test. The snow surface on sunny slopes was hot pow during peak daytime heating, and those same slopes had developed a thin zipper crust once the sun set behind the ridgeline. While overall snow depths have increased significantly of late, natural activity suggests likely trigger spots reside in shallow, rocky areas of slopes or those slopes that previously avalanched in December making it easier to impact weaker snow layers, and wide propagation remains a concern from slab connectivity across the terrain.