Southern San Juan
AvalancheJed Botsford · Mar 24, 2020 · Southern San Juan
Weather
Day was sunny with no wind. Temperatures ranged from -5 o -3 C. We spent the day ride riding in elevation from 9,200 to 11,1140 feet on all aspects.
Snowpack
I dug a pit on a 6 percent slope below tree line where my snowmobile had gotten stuck just to see the layers in the snow pack. Snow pack was 175 cm deep with 0 being the ground 175 being the top of the snow pack. There were concerning layers of buried surface hoar at 100, 108, and 125 cm. There was a consistent 51 to 63 cm of snow from the storm on March 18, Wednesday. On top of that fresh snow was an additional 6 cm of snow from over night. I did not complete a CT or ECT due to the low slope angle. We did not see any shoot cracks or feel whupping. snow on south aspects was bonding fast and becoming sticky by 2 in the afternoon.
Avalanche
Even though the avi report was a moderate level on all aspects and elevation we ended up on a north facing aspect at 11,140 feet. A snowmobiler in the group was high marking and had exited the slope when a R1, D1 persistent slab avalanche released. The avalanche propagated up from the high mark to a small set of cliffs, 60 feet above. The crown was 75 to 115 cm. The avalanche ran on a layer of buried facets at 108 cm matching what I found in my pit. The avalanche did not break down into lower layers or go to the ground.