Southern San Juan
AvalancheChris Bilbrey, Jason Konigsberg · Jan 31, 2019 · Southern San Juan
Weather
No wind and clear skies with warm temperatures.
Snowpack
Snow surfaces became moist on sunny aspect with crusts quickly forming in the afternoon. Shady aspects have a weak faceted surface.---We dug on both an east aspect and a northeast aspect with no propagating results in Extended Column tests. We found a few places to dig where there was not recent avalanche activity. This was not easy to find. Above a large and wide crown, in our northeast-facing snowpit, we found a 165 cm deep snowpack with a strong 4 foot thick slab. Under the slab is a one-finger minus layer of faceted snow that is strengthening and does not seem concerning.---Slopes that slid, slid to the ground. In these places about 6 to 8 inches of fist-hard faceted snow sits on a slick icy old bed surface. Repeater avalanches would be a big future concern in the La Plata mountains as more steep slopes slid then did not.
Avalanche
Too many avalanches to list. As mentioned in the snowpack description, this area saw an extensive avalanche cycle. We did not see any large avalanche paths intact and most big paths slid D3 in size. Equally impressive was the amount of avalanche activity below treeline with widely propagating avalanches through and around terrain features in treed terrain. Avalanches did not run at a maximum size relative to their path and we did not see much evidence of new trim lines or destruction of any large forested areas. Although these paths can run much bigger it is hard to say that the extent of this cycle, with almost all steep terrain avalanching could be matched.