Northern San Juan
AvalancheAmy Pertuz · Dec 8, 2018 · Northern San Juan
Weather
Sunny skies in mid day with clingy clouds on terrain and broken skies later in afternoon. Mild temps peaked in the mid 20s. Winds light, transitioning from SW to W by afternoon, with minimal blowing snow during the midday/afternoon but plenty of evidence of recent, significant, transport. Loading patterns suggest overnight winds from the S as well as SW.
Snowpack
A few inches of new, low-density snow on the surface did not change the load significantly, but the overnight redistribution by winds had, especially in the alpine. HS on BTL W'ly aspects is deepening enough to ski, but in many places has just enough recent load to be failing on basal facets easily. Aside from basal facets, a prominent faceted weak layer exists below the Thanksgiving storm layer, (now almost a meter below surface, NW TL slope) as well as a mid-storm weak layer from around Dec 1st (now around 60cm below surface, NW TL slope), which were found on aspects West through North through East near TL as well. The most prominently changed slopes from this overnight wind event are alpine W'ly and NW'ly slopes that show significant new wind-loading. Experienced localized collapses to 40 ft on BTL W'ly and NW'ly slopes that were below 30 degrees
Avalanche
A small windslab HS-N-R1-D1-u observed on a crossloaded W aspect ATL. Dry-loose activity within the new low density snow observed off rockbands at almost all elevations and aspects, sometimes entraining a fair amount of snow.