Southern San Juan
SnowpackChris Bilbrey Bill Nalli · Jan 6, 2020 · Southern San Juan
Weather
Moderate to strong northwest winds in the morning gave way to calmer conditions by mid-day. Temperatures remained cold under mostly sunny skies.
Snowpack
Snow surfaces have weakened and began to facet in wind-sheltered and below treeline terrain. This made for soft surface riding conditions but will be something to keep an eye on with our next load. A thin but breakable melt-freeze crust was observed on slopes that see direct sunshine. As we approached treeline, effects of the recent wind assault (strong N, W, and SW winds) were evident. Isolated portions of slopes were soft while others had a thin but supportable wind-skin. Climbing higher in elevation revealed a mix bag of chalky wind-board, sastrugi, and drum, hollow hard slabs ranging from 5 to 10 cm thick. We were unable to get these hard slabs to fail in long-column test but they are sitting above softer, decomposing snow grains that will act as a good collapsible layer if our next load adds enough stress. Alpine slopes have lots of variability in terms of snow depth with shallow, weak areas next to deep, stronger areas. As our next storm builds a new slab, it will be important to manage terrain selection to avoid those shallower, weak spots of slopes where rider-triggering is more likely as weaker snow will be closer to the new snow surface.