Signs of instability below treeline

CB Avalanche Center 2016-17 Observations

Location: Crested Butte Area
Date of Observation: 12/09/2016
Name: Zach Guy
Subject: Signs of instability below treeline
Aspect: North East
Elevation: 9400-10600

Avalanches: We skier triggered one small soft slab, failing on Dec 6th facet layer, about 8″ thick and 25 feet wide. Harmless in size, and managed like a storm slab. SS-ASc-R1-D1-I
Weather: Overcast, S-1, calm winds below treeline with a few plumes and gusts observed up high, mild temps.
Snowpack: Below treeline, the structure remains shallow and faceted, but we are starting to see signs of instability with the new snow. A few shooting cracks and one collapse observed today on NE aspects below treeline. There is about 6-8″ very soft slab over the Dec 6th near surface facet layer (1mm, F hard), with facets to the ground below that. In a few areas, there is some lingering 4F midpack, faceting slab, and we got one collapse where this was overlying ~2mm basal facets. This seemed to be a fairly isolated concern where we traveled, and saw no other signs of instability on various slopes up to 40 degrees in steepness. My biggest concern is when we put a real slab on our Dec 6th facet layer, which was widespread across every slope we traveled on.