Northern San Juan
AvalancheAnn Mellick Jeff Davis · Mar 25, 2021 · Northern San Juan
Weather
Broken cloudiness in the morning gave way to overcast skies and light snow by noon. Unseasonably cool with brisk SW winds above treeline
Snowpack
~8" of snow was measured at the Red Mountain Pass study plot on the morning of the 25th and snow continued to fall throughout the day. Southwest winds drifted the snow loading northerly and easterly slopes leaving drifts over 18" deep. The new snow was falling on a firm crust on many below treeline and sunny slopes and likely a layer of near-surface facets on slopes were the snow surface remined dry during the last warm spell. The snow bonded better to the crust on slopes at lower elevations than on alpine slopes. In general the snowpack in changing and becoming more dangerous as incremental loading continues to build storm snow avalanche problems over a snowpack that was in the process of shifting to spring. Digging on a west facing slope below treeline: water has made it way through the upper 50 cms of the snowpack, but the mixture of crust and facets that have developed during the most recent warming period are not confidence building. With the thick and firm surface crust these buried weak layers were not much of a problem today, but could become one with a bigger load or next week's rapid warm-up.
Avalanche
Small long running loose avalanche observed from steep rocky terrain on all aspects above treeline.