BC Zone Observation Report
Tuesday, December 20, 2016 at 12:00 AM
Forecaster, Crested Butte Avalanche Center
Crested Butte Area
Date of Observation: 12/20/2016 Name: Zach Guy and Scott Krankala Subject: Red Lady Crown Investigation Aspect: South East Elevation: 12,200 ft
Our crown profile was 142 cm deep. The failure layer is 2 – 2.5 mm facets/rounding facets at the ground, F+ in hardness. The slab at that location is 132 cm, mostly all .2 to .3mm 1F rounds. We did not identify a crust layer at this particular spot.
Investigated the skier triggered persistent slab avalanche in Red Lady Bowl, triggered 12/18/16 at approximately 3:30 pm. The slab was mostly all 1F in hardness, or a hard slab. The avalanche was unintentionally triggered by skier, from what appeared to be a shallow, rocky part of the slope. The crown on the skier’s right side ranged from 200 cm to 30 cm in height, averaging approximately 150 cm. We did not go to the crown on the skier’s left side, but it appeared to average about 100 cm in thickness. Based on Google Earth measurements, the skier’s right crown is 200 feet wide and the skier’s left crown is 1,500 feet wide. The debris ran 3,600 feet and a vertical fall of 1,500 feet. The avalanche was medium relative to its potential extent. The debris snapped numerous small to medium sized trees in the runout, and was large enough destroy a car. It failed in old, faceted snow and ran on the ground. The avalanche is classified as HS-ASu-R3-D3-O/G