Persistent Slab hunting on Mt. Emmons

CB Avalanche Center2017-18 Observations

Location: Crested Butte Area
Date of Observation: 01/29/2018
Name: Ben Pritchett & Eric Murrow

Subject: Persistent Slab hunting on Mt. Emmons
Aspect: North, North East, East, South East
Elevation: 9,000-11,000′

Avalanches: triggered several small loose facet sloughs on steep slopes below 10,500′ on north through east aspects.
Weather: warm day, no signs of wind
Snowpack: Went to find the threshold for where persistent slabs remain a problem. We know that our eastern end of our zone is so weak that below treeline in the upper brush creeks and cement creek areas, the generally too weak to propagate a crack. We also know that around Pittsburg persistent slab structures and still exist as evidenced by last Thursday’s remote trigger, and two known skier trigger slides in the Purple Palace area today (Monday January 29th). So we went to the in-between zone, closer to town, right on the margin of the snow belt.
Below 10,000′, we found rotten, faceted, trap door conditions on north through east slopes. Facet sloughing on slopes ~40+ slopes. Crusted on southeast aspects.
10-11,000′ seems to be the sweet spot for the lower margin for remnant persistent slab concerns. The slabs are losing strength, but still propagating in ECT’s and PST at around 10,000′. Above 10,000′, there’s no question that a hazard remains if you’re on a steep slope with wind consolidation from old drifting or steep sun-settled slopes just south of east.  At 10,900′ on a slope angle in the high 20’s, we triggered a 40′ wide collapse as we neared an east-southeast facing ridgeline, complete with shooting cracks.