2022/03/12 - Wyoming - South Fork Miner Creek, Sierra Madre Mountains

Published 2022/03/17 by Frank Carus - Bridger-Teton Avalanche Center

During a very dry January and early February, a layer of near-surface faceted crystals formed in the top 30 cm of the snowpack to the south in Colorado. This layer was buried in mid-February. A snowpit observation submitted to the CAIC on February 24, near Cameron Pass, showed a snow height of 190 cm. The snowpit showed that the snowpack instabilities were relegated to the upper half of the snowpack. At the beginning of March, Colorado and Wyoming experienced very warm temperatures with snow becoming wet at the snow surface. The snow refroze into a crust on March 4 on many aspects and elevations as temperatures cooled. From March 3 to March 6 the new snow that fell was accompanied by strong westerly winds in nearby mountains in northern Colorado which built a stiff slab over the crust. No wind stations exist in the area of this fatality although the snow profile performed in the course of this investigation shows a layer of hard slab just above the melt freeze crust. On March 8 and 9, 18” more snow fell on a dense slab formed by wind and settlement. Small facets 0.5 to 0.75mm were observed between the melt-freeze crust and the dense slab above. New snow added a load to this layer and depth to the resulting slab.

Those involved in this incident were two males from Rapid City, South Dakota. The survivor was 33 years old and the deceased was 58 years old. Both riders had significant experience riding in the area with the younger of the two having made eight trips to the region this winter. Each was active in snowmobile clubs in their home state and had attended avalanche safety seminars organized by visiting pro riders. Both were regular readers of CAIC avalanche forecasts. The survivor shared that the two had changed objectives from the Bridger Peak area to the Green Mountain area after reading the CAIC forecast on the day of the avalanche, believing that this was a more conservative terrain choice given the elevated avalanche hazard. Both were wearing avalanche beacons and airbag packs and carrying probes and shovels.

The two riders rode through forested terrain from the vicinity of Green Mountain and traveled south into the South Fork of Miner Creek. The pair were using a GPS to navigate and thought that they were just outside of the Wilderness boundary. The two avoided open slopes on their ride and noted no avalanche activity, cracking or collapsing earlier in the day. The snow was deep and challenging riding. As the pair made their way through the forest they entered the slope from the right, sidehilling across. The survivor attempted to turn and ride upslope but failed and turned back downhill and entered the forest below the avalanche path to turn around for another attempt at climbing the slope. He was approximately 50 yards from the bottom of the avalanche path. He paused to catch his breath and clear snow from his runners and noted that he no longer heard his partner's sled engine, who he assumed had made it to the top of the slope and was now awaiting him. Unknown to him, his partner had made the hill climb, but had then returned down the slope, triggering the avalanche at a convex roll in the terrain.     

After taking a break, the survivor rode into the clearing below the slide path and saw the avalanche debris. He then noted a handlebar poking out of the snow and rode up to the buried sled. He walked across the slope while initiating a beacon search, sinking to his waist in the soft and also blocky debris. He acquired a signal and walked 20 to 30 yards following the directional arrow on his beacon and found the lowest reading at 1.6 or 1.8 meters (5-6 feet) from a standing position. He made a positive strike with his probe pole on his first attempt and began to dig. The survivor encountered an extended arm and hand about two feet down and continued digging to the victim's head. The victim was wearing a full face helmet (visorless) and balaclava though the void was full of soft snow. He removed the deceased’s helmet and found no pulse or respirations. The survivor began CPR, continuing for 15 minutes, at which time he ceased this effort and called 911. The time was 1:02 pm. 

Soon after receiving the call, the Sheriff's Office dispatched Carbon County, Upper Platte Valley, and Ryan Park Search and Rescue teams on snowmobiles. Riders departed the Bottle Creek parking area at 1:53 pm. The team rode approximately seven miles on the groomed trail before leaving the trail to locate the supplied coordinates. The search was complicated by difficult, deep snow riding over unsupportive faceted snow in heavy timber, as well as being confused by multiple sled tracks inside the wilderness boundary. Coordinates from the 911 call are not always accurate which created uncertainty in the search team. At 4 pm a request was made for air support from Classic Air Medical in Rawlins and a helicopter arrived on scene at approximately 5pm. 

After terminating CPR efforts and placing the call to 911, the survivor left the scene of the incident and rode down the drainage to flag a route to assist rescuers. Unfortunately, rescue parties had passed by his intersection with the trail before he had placed a marker on the trail. 

The flight crew quickly located the incident site from above and confirmed the coordinates from the 911 call as the correct location. The flight crew then guided two searchers into the scene from the air. The time was 5:30pm with sundown to occur at 6:09pm. Due to the time of day, difficult riding and threat of further avalanche activity, searchers were recalled to the trailhead with the survivor and a plan was made to retrieve the deceased body the following morning. A team returned the following day extricated the deceased to the trailhead.

Forecasters noted that the season's snowpack remained complex due to the recent warming, faceting layers plus recent heavy snowfall. The Considerable rating carried with it the possibility of natural avalanches, two of which were noted by search teams that day. The presence of a variable thickness melt-freeze crust, variable snow depths and several very cold nights created complex layers with potential for faceting near the crust. In this case, the weak layer was very thin and yielded little feedback such as the whoompfing or collapsing often indicative of buried weak layers. The men involved in the incident had the right idea to change objectives to more conservative terrain, but hindsight suggests that the two may have ridden more aggressively as the day went on. This drift in the acceptance of risk can often occur in the absence of feedback. As is sometimes the case with buried weak layers, no obvious signs or red flags were apparent. Entering a small slope after several hours of riding with no signs of instability is easy to understand.

This team was properly equipped, read the forecast and made adjustments to their plan. Riding during elevated avalanche conditions requires some sort of plan to resist the effects of a negative feedback loop. Avalanche professionals, ski guides and other savvy recreationists can use a “no-go” list and adhere to it no matter what conditions they may or may not encounter in the field. Such a list may be specific, like certain runs or slopes, or more general, like slopes over 30 degrees or north facing terrain. 

Rescuers tested the deceased pack after the recovery and found it operated normally. The small size of the slope and short distance traveled in the flow suggests two things. One, the victim had no time to pull the handle and two, even if deployed, the airbag would likely have made no difference due to the short amount of time for particle segregation to play out. These facts add weight to the concept that avalanches don’t need to be large to be dangerous. This death was confirmed as asphyxia by autopsy. Multiple factors determine the speed with which asphyxia occurs.

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

Bridger-Teton Avalanche Center staff would like to thank the Carbon County Sheriff's Department, especially Deputy Pat Patterson, the Department’s SAR team for escorting BTAC staff to the scene in challenging conditions.  We would also like to thank the survivor for openly sharing information about this tragic incident.

Frank Carus

Director, Bridger-Teton Avalanche Center