Northern San Juan
AvalancheColin Mitchell · Feb 1, 2018 · Northern San Juan
Weather
Warm temperatures, moderate winds and overcast. Mostly high thin clouds with some sun poking through. Some grey storm clouds were blowing in from time to time. Radiation was intense when the sun shone through the cloud cover.
Snowpack
Surface conditions, and really the whole snowpack, were highly variable. The areas we traveled were mostly E and S aspects. Near and below treeline, micro terrain features defined the snow conditions. We could still find the thin, mid-pack slab that sits over our basal depth hoar layer on N aspects, even tiny ones. Other aspects had a softening sun/temperature crust which was quite pronounced and widespread. Thin wind slabs, wind-worked snow and crusts were evident around terrain features and really on all open terrain. This layer was starting to soften from faceting below about 11,000 feet. Above treeline, the snowpack was thin, and hard slabs and facets dominated the structure. The wind event that we had on 1.21 worked over the snow and many slopes were stripped. Most areas with snow harbored a layer of facets at the ground, with an old, thin wind slab/crust on top. Others were holding hard wind slabs 1-2' thick, presumably over the same weak layer. This structure is likely more pronounced and widespread on northerly-facing slopes, and could potentially produce a large hard slab avalanche. Southerlies were softening and moistening at all elevations by afternoon.
Avalanche
Old crowns are visible in many locations near and below treeline, but nothing newer than our last reported slide on 1/29