Cement (aka Sandbox) Mountain

CBAC CBAC Observations

Date of Observation: 03/20/2022
Name: Zach Guy

Zone: Southeast Mountains
Route Description: Traveled on West to North aspects below treeline on Cement Mountain, up to 10,500 ft.  This is one of the shallowest parts of our forecast area.

Observed avalanche activity: Yes
Avalanches: Ski cut a small persistent slab on a small terrain feature facing NW. The slab was just under a foot thick and failed on the mid-February facets.
Weather: Thin overcast and mild temps made for good greenhousing midday, which moistened surfaces on northerly aspects. No wind where I traveled, but I could hear it higher up.
Snowpack: On northerly tilted aspects, the mid-February “sandbox” layer is uniformly weak and lousy; the key ingredient for instabilities here is the presence of a slab. At the lowest elevations, below about 9,700 ft, the slab is thinner and faceted out with ski pen consistently going through an unsupportive upper snowpack. I got numerous collapses, but cracks would only propagate 5 or 10 feet at most. As I gained elevation, the upper snowpack became more supportive and slabs were a bit thicker and denser (about 35 cm, 4F). I got widespread collapsing and shooting cracks, typically radiating 20 to 50 feet, and a couple up to 100 ft. Stability tests produced easy propagating results on the sandbox layer, which is 2-3 mm in size and fist hard. HS averaged 80 to 120 cm. The two pronounced start zones that I traveled near had already avalanched back in late February and the upper snowpack was all faceted on those terrain features with no concerns.
Snow surfaces got moist on northerly aspects and I skier triggered numerous rollerballs and pinwheels, but nothing gained enough volume to turn into a wet loose slide.