Northern San Juan
SnowpackAmy Pertuz · Feb 17, 2023 · Northern San Juan
Weather
A cold morning with valley inversions warmed quickly at upper elevations, with clear skies and bright sun. Winds were light out of the north. Temperatures crested freezing below treeline, and just barely edged above it at upper elevations. Temperatures felt crisp in the alpine despite abundant sunshine. High thin clouds moved in in the afternoon.
Snowpack
Storm snow from the week measures 65cm here, and has not settled much since it fell. Warm temperatures Friday created warmed surfaces on lower-elevation slopes, but the morning inversion helped to keep this limited. On a west aspect, warm temperatures thickened surface snow by afternoon at tree line, but snow remained dry. On westerly aspects, a thin crust was found at the new/old interface, with small facets below. The crust was less than half a centimeter below tree line and thinned as elevation increased, and was intermittent above 11,500ft. This was most reactive at the upper reaches of the below-treeline elevation band, where the crust was less stout but still relatively thin. Compression Tests produced moderate results (CTM 13), and an Extended Column Test produced a propagating failure on 15 taps (ECTP15). This interface was unreactive to skier pressure on small test slopes. On near and below-treeline northwesterly slopes, the storm snow sits on small near-surface facets which propagated in an Extended Column Test(ECTP20) but showed signs of bonding. I could not get any steep northerly below-treeline test slopes to move on this layer. No cracking or collapsing.