Southern San Juan
AvalancheChris Bilbrey · Jan 7, 2020 · Southern San Juan
Weather
The sun was out and in full effect. Temperatures climbed above freezing at 11,000 feet and this allowed southerly-facing slopes to soften up. A light breeze along ridge tops was welcomed.
Snowpack
The La Plata Mountains were not spared by the recent wind assault and may have seen the brunt of the stronger winds. Isolated areas on many northerly and westerly-facing alpine slopes are stripped to bare ground. That is quite impressive seeing that this range received a lot of snow during the prior six week stormy period with generally above average snow cover. Hollow, hard slabs galore on open slopes and in cross-loaded terrain features on multiple aspects - even below the timber line. Wind-sheltered, shady snow surfaces have weakened and faceted. Slopes that see direct sunshine have a thin melt-freeze crust covering softer, decomposing fragments and near-surface facets. Both of these surface scenarios are not a concern until our next loading event which then will become the perfect collapsible weak layer for future loads to fail on. A snowpit on an east aspect at treeline found three facet-crust layers in the top meter of the snopwack, but none of these layers produced propagating test results in ECTs. Recent warm temperatures are helping the snopwack settle and stiffen making rider triggering more difficult on buried weak layers. Outside of old avalanches that ran sometime in the previous 3 to 4 days, no signs of instability observed where we traveled.
Avalanche
Estimated these avalanches ran sometime on 1/3 or early morning hours of 1/4.