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Avalanche: Big Cottonwood Canyon

Observer Name
Engelhard
Observation Date
Friday, February 28, 2014
Avalanche Date
Friday, February 28, 2014
Region
Salt Lake » Big Cottonwood Canyon
Location Name or Route
Natural and Human Triggered Avalanche Cycle
Elevation
10,600'
Aspect
Northeast
Slope Angle
Unknown
Trigger
Snowboarder
Trigger: additional info
Unintentionally Triggered
Avalanche Type
Soft Slab
Avalanche Problem
Wind Drifted Snow
Weak Layer
New Snow
Depth
14"
Width
150'
Vertical
800'
Caught
1
Carried
1
Comments

The above details are for the Lackawaxan Slide that was previously reported. It was a Storm Slab/Wind Slab made more sensitive and cohesive as a result of wind loading. This was a Soft Slab of 4 finger hardness. It was a D2.5 in size. The victims' partner then proceeded to initiate another slide in the chute to the riders right of the aforementioned slide. He did not go for a ride. The total width of these two slides was approximately 350 feet, and the combined runouts were tied together as they came out of the cliff bands. This and many other slides appeared to have a weak layer that was just above the old snow interface, and it was a mixture of grauple and precip particles that had rimed stellars and light density snow. The initial snow that fell at the beginning of the latest event appeared to bond, yet after this first wave of high density/warm precip, there was a period when colder snow grains fell. At lower elevations, there was more grauple in the initial first 4 to 5 inches. Photos of this slide on the previous report by Kellen. His picture was better than mine.

Also observed was an 85 foot wide slide in the Chutes below the Wolverine Bowl. The riders right chute was also human triggered and it broke out approximately 100 feet/6 turns down the the slope. It was hard to tell if the victim went for a ride or was able to escape. It propagated as it descended just like all the other slides observed. As it broke out of the chute it propagated out below the cliff lines that form the chute. This slide as well as all others ran well into the flats...much longer that would be expected. It was approximately 12 to 14 inches deep and was a D1.5 in size.

Slope cuts in the morning hours were yielding easy shears and fractures in the new snow only on slopes with angles > 35 degrees.

The good riding conditions experienced in the morning hours changed significantly after 1230 when there was an impulse that came through with Moderate to Strong Winds out of the SW; and this was accompanied with off and on precip, and Intense Blowing Snow. At that point the snowpack became upside down in almost all terrain, and this was exacerbated in any areas that were receiving even Light Winds. At least 5 naturals were observed in the Wolverine Cirque, with the Y Chute (aka Grannies) running in both nostrils. These were triggered by small cornice falls. And, this particular slide ran at least 150 feet on the low angle/flat moraine runout. After viewing this slide from the Peak of Wolverine an attempt was made to take a closer look at the crowns and possibly descend down the Y Chute. Due to rapid reloading and confirmation of the excessive nature of the runouts observed this mission was abandoned. Photos taken of this slide and the Wolverine Bowl slide were not of good quality due to the flat light, cloud cover and precip.

During the last part of the afternoon there were extreme sensitivities observed on all aspects, with those receiving even limited wind loading exhibiting unusual highly sensitive results. These heightened conditions included terrain at mid elevations. Cracking was observed on 25 degree slopes with slab failures of one finger hardness on slopes of 30 degrees, and these avalanches were propagating around terrain features into adjoining gullies and chutes.

Hazard in the mid to late afternoon escalated to High

Coordinates