CAIC: Colorado Avalanche Information Center

2017/02/03 - Colorado - Above Copper Creek, near Gothic

Published 2017/03/20 by Zach Guy - Forecast Staff, Crested Butte Avalanche Center


Avalanche Details

  • Location: Above Copper Creek, near Gothic
  • State: Colorado
  • Date: 2017/02/03
  • Time: 2:00 PM (Estimated)
  • Summary Description: 1 skier caught, carried, and injured
  • Primary Activity: Backcountry Tourer
  • Primary Travel Mode: Ski
  • Location Setting: Backcountry

Number

  • Caught: 1
  • Partially Buried, Non-Critical: 0
  • Partially Buried, Critical: 0
  • Fully Buried: 0
  • Injured: 1
  • Killed: 0

Avalanche

  • Type: HS
  • Trigger: AS - Skier
  • Trigger (subcode): u - An unintentional release
  • Size - Relative to Path: R2
  • Size - Destructive Force: D1.5
  • Sliding Surface: O - Within Old Snow

Site

  • Slope Aspect: W
  • Site Elevation: 12200 ft
  • Slope Angle: --
  • Slope Characteristic: Convex Slope,Gully/Couloir

Avalanche Comments

Characteristics of the avalanche are estimated from photos, descriptions from the reporting  party, and from information gathered during an on-site visit.  The avalanche appeared to be a hard slab (up to Pencil- Hand Hardness Index), unintentionally triggered by a skier, small relative to the path, and large enough to knock a person over (HS-ASu-R2-D1.5-O). The avalanche broke on old faceted and/or crust layers and released on a small, concave feature on a west-facing slope above treeline, at an elevation of 12,200 feet. The avalanche broke an estimated 12 to 15 inches deep and approximately 20 feet wide, and ran approximately 1,350 vertical feet, carrying and depositing the skier on top of about 3 feet of debris.  

Weather Summary

One of the largest storms in the past 30 years brought significant snowfall to the Elk Mountains between January 1st and January 14th. The Gothic town site (located 2.2 miles west-southwest of the avalanche site at 9,600 feet) recorded 9.6 inches of snow water equivalent (SWE).  High pressure brought dry weather until January 19th.  Active weather arrived from January 19th until January 24th, with two subsequent storms producing a total of 22 inches of snow (1.64 inches of SWE) at Gothic.  Winds increased through this unsettled period, averaging 23 mph and gusting up to 74 mph out of the southwest by the end of this system at the Elkton weather station (elevation of 11,100 ft., 4.9 miles west of the avalanche site).  The next two days brought unsettled weather with minimal accumulations of new snow as winds eased and shifted to the northwest. 

The Elk Mountains remained under dry, mostly clear skies and cool northwesterly flow from January 27th until the avalanche incident on February 1st.  At the Elkton station, temperatures gradually increased through this dry period from a high of 12 degrees Fahrenheit (F) on the 27th to a high of 31F on February 1st.  Winds remained steady out of the northwest gusting into the 30’s and 40’s mph range.  On February 1st, the day of the avalanche incident, skies were scattered, and winds backed to the southwest, averaging 19 mph and gusting up to 52 mph at Elkton. Temperatures reached a high of 31F with an overnight low of 25F. 

 

Snowpack Summary

The gully feature where the avalanche occurred  faces northwest and is subject to heavy cross-loading and wind-scouring from predominantly westerly winds.  The structure on the skier’s right side of the gully, consisted of either an unsupportive, fully faceted snowpack (less than 50 cm deep), or a faceted snowpack capped by a breakable melt-freeze crust. There were shallow hard slabs 5-12 cm thick over this structure behind a few isolated trees and in concavities on this slope.

Following the very large storm during the first half of January, the snowpack in this terrain was cross-loaded and deep on the skier’s left side of the gully and wind scoured and shallow on the opposite skier’s right side.  The brief dry spell in mid-January caused a spatially variable thin melt-freeze crust to form on the sunnier, skier’s right side of the feature where the slide was triggered.  Faceting occurred throughout this shallow, wind-scoured snowpack during this time, leaving a weak snowpack structure.  In isolated features, small and thin hard slabs developed over a faceted and/or melt-freeze crust base. During the week of dry weather prior to the accident, the snow surfaces became stiffer. On the day following the accident, wind eroded the crown, making observations difficult.  Investigators traversed across portions of the same slope and observed a generally weak and shallow snowpack, but lacking a slab due to wind scouring. It appears that the skier-triggered slab avalanche was an isolated drift over this weak structure, that  likely failed on a crust or faceted snow layer. 

 

Events Leading to the Avalanche

On February 1st, 2017, two backcountry skiers, (Skier 1 and Skier 2) ascended the sub-ridge of White Mountain above Copper Creek with the plan to descend one of the northwest facing gullies from the ridge’s high point, locally known as Zachary’s Peak.  Both skiers were highly experienced in backcountry travel and were well acquainted with the terrain of the day’s objective. They had both read the avalanche advisory that morning.  The party felt one collapse on a low-elevation, south-facing slope.  As they gained elevation, they noted strong winds but no snow transport.  The two skier’s scouted the upper portion of their descent from a vantage point along the climb, noting the previous wind loading and scouring patterns. Skier 1 began the descent first, descending about 100 feet, crossing over the point where the slide later broke.  Skier 1 performed a few hand pits on the first pitch of the slope.  After the first pitch, Skier 1 traversed skier’s right to a shallow, rocky area as Skier 2 began descending.  Skier 2 had planned to traverse further skier’s left to cross into another gulley that appeared to be holding better quality, wind-sheltered snow.  

Accident Summary

At approximately 2 p.m. Skier 2 was descending along the same route as Skier 1’s route when he unintentionally triggered a small, hard slab avalanche. Skier 2 was knocked over by the moving debris but was almost able to self- arrest. He was dragged over a rock band and carried down slope in moving debris with one ski still on. The debris carried Skier 2 approximately 1,350 vertical feet down the prominent gully, washing him over a sloping cliff band about 80 feet tall.  The avalanche came to a stop near the apron of the cliff band, depositing Skier 2 on top of about 3 feet of debris. Skier 2 sustained numerous serious injuries. 

Rescue Summary

Skier 1 watched the avalanche occur from high on the avalanche path.  He watched his partner get carried down slope out of site and reappear in the runout on top of the avalanche debris.  Skier 1 hastily descended the slope along the skier’s right side of the avalanche path and found Skier 2 alert and oriented, both skis off on the surface of the debris, and obviously injured. Skier 1 recovered one of the missing skis and was able to adjust one of his own skis to fit the boot of Skier 2.  He also performed medical care on Skier 2’s injured elbow, while adding extra jackets to keep him warm.  Skier 2 was able to descend under his own power down the remainder of the avalanche path towards Copper Creek Trail.  As Skier 2 was descending, Skier 1 checked his cell phone and was surprised to see he had a cell phone signal.  At approximately 2:20 p.m., he made a call to 911 to request emergency support.  Emergency dispatch initiated a response from Crested Butte Search and Rescue (CBSAR) as the two skiers continued to slowly egress down the Copper Creek Trail.  A group of CBSAR members snowmobiled from Snodgrass Trailhead to Copper Creek Trail and met the pair of skiers around 4:00 p.m.  CBSAR redressed Skier 2’s wounds, provided oxygen, medication, and layering for hypothermia, and snowmobiled him to the town site of Gothic.  They stopped at a cabin in Gothic to warm Skier 2, who was suffering from hypothermia.  CBSAR then snowmobiled Skier 2 in a rescue toboggan to the Snodgrass Trailhead, where he was transferred to the care of EMTs.  A more detailed write-up of the rescue is here: http://crestedbuttenews.com/2017/02/local-backcountry-skier-caught-in-avalanche-above-copper-creek/

Comments

This was a hard slab of wind-drifted snow that failed on an old weak layer.  This type of avalanche often breaks unexpectedly, often above a rider rather than at their feet, and without warning signs.  Unfortunately, this relatively small avalanche resulted in serious injuries because of the severe terrain consequences.  The long-running terrain and cliff band exacerbated what would normally be considered a harmless avalanche.

This was a very challenging instability to identify and predict.  The obvious clues, such as collapsing, cracking, recent avalanche activity in the area, and active wind- or snow-loading, were absent, except for one collapse at a lower elevation. The avalanche danger was rated MODERATE (Level 2), with the advisory that day warning of dense, drifted slabs over a variety of old surfaces at higher elevations from recent winds.  The slide was triggered from the wind-scoured aspect of the slope, where you wouldn’t expect to find wind-drifted slabs.   This is the tricky nature of traveling in complex, above treeline terrain, and the consequences in these terrain features are often unforgiving.  The snowpack on these kinds of slopes is often highly variable and can be unpredictable..  This group was unfortunate to cross a pocket of wind-drifted slab on what was an otherwise wind- scoured and relatively stable pitch.  

The responding party member made excellent route decisions descending to his partner after the accident by choosing the most wind-scoured route so as not to trigger additional hang-fire or get caught in a subsequent slide.  Their ability to communicate with emergency response teams, and CBSAR’s skillful and efficient response all contributed to a successful rescue, one which could have easily had a different outcome.  Carrying a charged cell phone and/or an emergency locator beacon are invaluable for emergencies in the backcountry, as is being prepared for medical treatment and hypothermia.  

 

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