Northern San Juan
SnowpackChris Bilbrey Bill Nalli · Dec 30, 2019 · Northern San Juan
Weather
Abundant sunshine with cold temperatures and light ridge top winds.
Snowpack
Like many other places in the San Juan's, the Rico Mountains have a deep snowpack for the end of December. Signs of unstable snow were non-existent until we climbed near treeline and traveled in wind-drifted terrain. We initially observed evidence of wind sculpting along treed ridges above 11,000 feet that transitioned to stiff, hollow wind drifts as we climbed higher in elevation. A snowpit on a southeast-facing slope revealed multiple buried crust with weaker snow below a newly formed wind-slab that ranged from 5 to 10 cm thick where we traveled. An Extended Column Test yielded an ECTP1 below the 1F wind-slab and failed on F hard storm snow below. Despite this test result, we found similar wind-slabs on south, southeast, and east-facing terrain near treeline stubborn to ski pressure and isolated cracking below skies that did not propagate outward. A natural avalanche on an adjacent slope but above treeline demonstrated how a shallow Wind Slab avalanche could step down to deeper persistent weak layers creating a larger slide.