CAIC: Colorado Avalanche Information Center

2021/02/22 - Wyoming - Broken Thumb Couloir, Peak 9,975 (25 Short), Grand Teton National Park

Published 2021/03/27 by Nick Armitage and Lisa Van Sciver - Grand Teton National Park

Avalanche Details

  • Location: Broken Thumb Couloir, Peak 9,975 (25 Short), Grand Teton National Park
  • State: Wyoming
  • Date: 2021/02/22 (Estimated)
  • Summary Description: 1 backcountry tourer caught and killed
  • Primary Activity: Backcountry Tourer
  • Primary Travel Mode: Snowboard
  • Location Setting: Backcountry


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


  • Type: SS
  • Trigger: AR - Snowboarder
  • Trigger (subcode): u - An unintentional release
  • Size - Relative to Path: R2
  • Size - Destructive Force: D2
  • Sliding Surface: S - Within Storm Snow


  • Slope Aspect: NE
  • Site Elevation: 8800 ft
  • Slope Angle: 38 °
  • Slope Characteristic: --

Avalanche Comments

On February 22, 2021, in Grand Teton National Park, a group of two split-boarders and one skier toured from Taggart Lake Trailhead up 25 Short to descend the Broken Thumb Couloir into Avalanche Canyon.

Upon descent, the 33-year-old split-boarder was leading the group down through steep trees and rocky terrain to the entrance of the couloir, when he triggered an avalanche that carried him through the confined, rocky couloir and over a 50-foot rappel. He was carried approximately 800 vertical feet and stopped on a tree.  He was partially buried with his head under the snow.  The initial findings for the cause of death by the first responders were of significant trauma. 

The avalanche was estimated at 150-200 feet wide, 2 feet deep at the maximum depth, and ran a total of 1,100 vertical feet.  This relatively small avalanche occurred directly above steep, rocky, and vertical terrain and took the snowboarder on an un-survivable fall.  The avalanche was reported as a recent wind slab (SS-ARu-R2-D2-S).

Weather Summary

The month of February was stormy with snowfall most days starting January 27. The Surprise Meadow snow station at 9,580 feet and Surprise Pinnacle wind station at 9,770 feet are both located about 2 miles to the north of the accident site, and the Summit wind station at Jackson Hole Mountain Resort (JHMR) is located about 9 miles to the south of the accident site. These are the weather stations used for the following data. 

Beginning February 12, snow fell daily leading up to February 22, with an estimated 65 inches of snow with over 5 inches of snow water equivalent, and since January 27, there was a total of 136 inches of snow at the Surprise Meadow snow station. In the 3 days prior to the accident, there was an estimated 13 inches of snowfall, and Summit winds averaged 18 to 22 mph from the west-southwest veering to the north-northwest. 

On February 22, a northerly flow aloft brought overcast to obscured cloud cover. The 0500 hours (hrs) temperature at Surprise Meadow was 28 degrees, which was the high temperature for the day.  Summit winds were west-northwest at 27 mph with the Pinnacle winds south-southwest at 11 mph. During the day, Summit winds backed to the west-southwest averaging 29 mph, while the Pinnacle winds veered to the southwest and averaged 16 mph. The high winds at both weather stations was recorded at 0500 hrs, with a maximum gust to 64 mph on Summit and 68 mph at the Pinnacle.

Snowpack Summary

February’s continuous storm had the Bridger-Teton Avalanche Center’s hazard rating at Considerable or level 3 on February 22. Persistent deep slab and wind slab avalanche problems were listed in the daily forecast.

From the previous 3 weeks of snowfall, there was abundant snow available for transport and for several days leading up to the accident, sustained ridgetop winds were in the upper teens to 20s with gusts into the 30s to 60s. These weather conditions typically form winds slabs, and the mountains can cause the winds to blow a variety of directs forming slabs on many aspects. 

In the week prior to the accident, many avalanches ranging in size 2 to size 4 were reported in the Grand Teton National Park. On February 17, 18, and 21, skiers triggered soft wind slabs with crown depths up to 2 feet deep. On February 21, evidence of a deep slab avalanche cycle, which likely occurred on February 20, were observed with crown faces 8 feet deep. There were also two other fatal avalanche accidents in the Bridger-Teton Forecast area during this week.

Due to the serious natures of the terrain and more snowfall and strong winds on the days following the accident, the investigation was not conducted at the site of the avalanche crown. 

A snow profile was done at 9,600 feet on a north aspect at the top of the descent line before entering avalanche terrain. The height of snow in this location was 350cm (11.5 feet). The snow profile was 150cm (59 inches) deep and revealed a mostly stable snowpack of decomposing fragments, wind packed rounds, and rounded grains. In stability tests, there was no propagation and moderate strength failures 30 to 35cm (12 to 14 inches) below the surface. 

Accident Summary

On February 22, Nick (roommate and long-time friend of Matthew Brien) and Caitlin left Taggart Lake Trailhead at 0750 hrs with plans to ski a north facing couloir off of 25 Short called Turkey Chute.  

At approximately 0800 hrs, Matthew Brien (snowboarder), Brad (snowboarder), and Matt H. (skier) arrived at Taggart Lake Trailhead.  They discussed whether they should go to the Broken Thumb Couloir, expressing some concerns for safety and “getting over their heads or getting into trouble”.  The group had read the Bridger-Teton Avalanche Center forecast for the day and discussed the recent wind loaded slopes.  Brien had skied a south facing couloir on February 21 off Shadow Peak into Avalanche Canyon and had discussed the wind effect in that area.  The group ultimately decided to bring ropes and harnesses to “take a look at” the Broken Thumb area and left the trailhead around 0815 hrs.

During the ascent of 25 Short, the party of three caught up to Nick and Caitlin. They re-discussed both groups’ plans for the day and then continued up together for a little while eventually separating as they neared the top of 25 Short.  

Nick and Caitlin stopped a couple hundred feet from the top of 25 Short due to the high winds.  They decided to descend the north ridge of 25 Short to ski a more conservative and less wind effected line further to the east.  They did not bother to look at the entrance to Turkey Chute because of its exposure to the recent wind load.  

At about 1100 hrs, the group of three reached the top of 25 Short and began to transition to descend the Broken Thumb Couloir.  Matthew Brien led the descent with Brad and Matt H. following one at a time. They utilized FRS (Family Radio Service) radios to communicate positioning and movement.  After what they described as three pitches of riding/skiing, the group stopped together at 9030 feet approximately 300 feet above the entrance to the confined Broken Thumb Couloir. 

Brien began riding the pitch into the top of the couloir when the slope avalanched 50 to 100 feet above his location. Brad yelled “Slide! Slide! Slide!” into his FRS radio channel 19-1.  Brad and Matt H. lost sight of Brien as he was carried into the couloir by the avalanche.

Nick and Caitlin were beginning to ski a couloir approximately .5 miles down canyon to the east. They decided to turn on their FRS radios to coordinate their descent.  Because Nick and Brien ski together regularly, they both use FRS channel 19-1.  When Nick and Caitlin turned on the radios, they heard an excited voice, which they thought was Matthew Brien, yell “Avalanche!” on the radio. 

Rescue Summary

Brad and Matt H. were in a safe location about 200 feet above the crown line and approximately 300 feet from where they last saw Brien.  After a few failed attempts to reach Brien on the radio, Matt H. called 911 at 1200 hrs.  His call was forwarded to Teton Interagency Dispatch Center who relayed the initial report of the information to the park rangers.  Matt H. then said he was going to hang up to attempt a rescue and will probably not have cell service on scene. Brad and Matt H. then descended the soft bed surface down through the couloir to the rappel.

Nick and Caitlin skied west, up-canyon, to the apron of the Broken Thumb Couloir run-out and Nick began a transceiver search as he entered the debris field.  Nick located Brien with his transceiver and began excavation.  Brien was bent backwards around a tree with some of his helmet, boots, and pack out of the snow.  Matt H. arrived on scene a few minutes after Nick and used his hands to dig around Brien’s helmet and face.  Brien’s airway was buried 6-10 inches deep. Matt H. noted that Brien was pulseless and apneic.  Nick and Matt H. made a quick snow platform, completed excavation, and although they notice significant trauma, began CPR.  Caitlin and Brad arrived on scene after approximately 5-10 minutes of CPR and assisted with the resuscitation efforts. 

Simultaneously at 1240 hrs, Teton County Search and Rescue (TCSAR) helicopter 38HX piloted by Steve Wilson arrived at a landing zone on the Moose Wilson Road in Grand Teton National Park to pick up rescuers.  At 1253 hrs, helicopter 38HX with rangers flew over the scene and saw bystanders doing CPR on a patient. The pilot and crew determined that a short-haul rescue was not viable due to high winds and poor visibility.  Two of the rangers were let out of the helicopter on Taggart Lake approximately 1.5 miles to the east of the accident site and began to ski up Avalanche Canyon to the scene at 1301 hrs.  

After approximately 25 minutes of CPR, Brien did not regain a pulse, and the group stopped CPR. They then constructed an improvised litter with a rescue tarp and began moving downhill to a safer location. At 1346 hrs, the rangers arrived in the area and met the group pulling Brien down canyon on the east side of the Broken Thumb runout.  In a relative safe zone, the rangers relayed the patient’s condition to Dr. Will Smith (Medical Director for Grand Teton National Park) who terminated further resuscitation efforts and called the time of death at 1358 hrs. 

By 1411 hrs, Brad, Matt H., Nick, and Caitlin began skiing down canyon to the Taggart Lake Trailhead. The rangers received equipment from Helicopter 38HX to package Brien and he was long-lined with the helicopter to the landing zone on the Moose Wilson Road.  By 1615 hrs, all parties involved with the accident had skied out of the backcountry to the Taggart Lake Trailhead. 


All of the fatal accidents that we investigate are tragic events.  We do our best to describe each one to help the people involved and the community to better understand them.  We offer these comments in the hope that it will help people to avoid future avalanche accidents. 

This accident occurred on serious terrain above a large cliff. Due the exposure of this terrain, this event was not only an avalanche accident but also a mountaineering accident. All three avalanche fatalities that happened in the Bridger-Teton forecast area this week occurred in steep terrain exposed to terrain traps. When natural and human triggered avalanches are happening, terrain selection is essential.  All the individuals involved in this incident had at least a level 1 avalanche class and significant experience in avalanche terrain.    

This accident was investigated by Nick Armitage and Lisa Van Sciver. Dylan Elder and Luke LeMaire conducted the snow analysis. The information was provided by the Park Rangers and members of the party. 




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Figure 7: A snowpack profile preformed on February 24, on a similar aspect to the accident but 800 feet higher than the location of the avalanche. This location was selected to avoid entering avalanche terrain.