- Location: Maroon Bowl, west of Aspen Highlands
- State: Colorado
- Date: 2018/04/08
- Summary Description: 2 sidecountry riders caught, 1 killed
- Primary Activity: Sidecountry Rider
- Primary Travel Mode: Ski
- Location Setting: Accessed BC from Ski Area
- Caught: 2
- Partially Buried, Non-Critical: 0
- Partially Buried, Critical: 0
- Fully Buried: 0
- Injured: 1
- Killed: 1
- Type: SS
- Trigger: AS - Skier
- Trigger (subcode): u - An unintentional release
- Size - Relative to Path: R2
- Size - Destructive Force: D2
- Sliding Surface: Unknown
- Slope Aspect: N
- Site Elevation: 11375 ft
- Slope Angle: 38 °
- Slope Characteristic: Concave Slope,Sparse Trees
This was a skier-triggered, soft-slab avalanche that was small relative to the path and had the destructive force to bury, injure or kill a person (SS-AS-R2-D2-I/O). It is unknown if the avalanche broke at the new/old snow interface, or on weak snow a few inches below this interface. The track showed that the avalanche stepped down into older snow in some spots. The crown face appeared to be about 16 inches deep, and 160 feet wide. The avalanche initiated on a steep, north-facing, near-treeline slope and ran up to 500 vertical feet into sparse trees.
The avalanche broke at a subtle, mid-slope convexity, leaving a significant amount of snow in higher-elevation start zones and lingering hazard above the fracture line. The terrain in the track was open glades. A similar avalanche released sympathetically a couple hundred feet lower and skier's left of the triggered slide.
Aspen Highlands Ski Patrol (AHSP) maintains the two weather stations closest to the accident site, Cloud 9 (10,828 feet; 1.1 miles north-northeast) and Loge Peak (11,625 feet; 0.56 miles north-northeast). From April 1 to April 5, the ski area and adjacent backcountry saw variable conditions typical of early spring weather. There were a couple inches of new snow, and above freezing daytime temperatures with below freezing nighttime temperatures.
On April 6, an unusually warm and wet storm moved into western Colorado. It began with above-freezing temperatures to nearly 12,000 feet and rain as high as 11,000 feet. Temperatures cooled as the storm progressed and snow levels dropped.
AHSP measured less than an inch of new snow on the morning of April 6, and two inches of dense new snow on the morning of April 7. On the morning of April 8, the day of the accident, AHSP measured 8 inches of new snow, with another 1.5 inches later that morning. The storm total from April 6 to the time of the accident was 12.2 inches of snow with 1.7 inches of snow water equivalent. The height of snow rose 9.5 inches during the storm.
Loge Peak recorded 24-hour maximum/minimum temperatures of 33F/26F and 33F/21F on the mornings of April 7 and 8, respectively. Wind speeds between midnight and 9:00 AM April 8 averaged 24 mph, with gusts to 63 mph. The winds blew from the northwest.
On the day of the accident, skies alternated between obscured and broken. Air temperatures peaked at 29F at 1:00 PM. Wind speeds dropped to 5 to 12 mph from the northwest.
In the Aspen area, the primary avalanche concern during most of the 2017-18 winter was a layer of weak facets and depth hoar near the ground. By late March, this layer had hardened and sintered, and other concerns rose to the fore, including a mid-pack persistent weak layer and wet snow avalanches.
On April 1, with the avalanche danger rated Moderate, a CAIC forecaster and partner conducted fieldwork in Maroon Bowl. The forecaster noted that the top few inches of the snowpack was a layer of soft (F on the hand-hardness index) rounds with some signs of near-surface faceting. The soft snow at the surface in the April 1 profile may have formed the weak layer for the avalanche on April 8.
On April 9, two CAIC forecasters conducted a snow profile on an open slope just south of Green Trees (11,650 feet, northwest), where Skiers 1 and 2 exited the ski area. Forecasters found a layer of dense, settled (Fist-hard) storm snow roughly 10 inches thick. The height and density of this layer closely match the snowfall measured by AHSP on the morning of April 8. The storm snow sat above several thin but hard crusts. Snowpack tests did not propagate at this interface at that time.
Events Leading to the Avalanche
Two skiers (Skier 1 and Skier 2) went to Aspen Highlands ski area on Sunday, April 8 with the intention of skiing into Maroon Bowl, a backcountry area often accessed from the ski area. Their plan was to ski a treed, northwest-facing, near-treeline slope known locally as Green Trees, and then ascend the west side of the bowl to a rock outcrop under a subtle ridge that splits the tracks of two northerly runs, N5 and N6 (Figure 5). They planned to descend the lower slopes of N5 and exit out the bottom of the bowl to the Maroon Creek Road.
They had hoped to execute their plan early in the day, but portions of the ski area were closed while the ski area completed avalanche mitigation and morning run checks. Skiers 1 and 2 rode in-bounds waiting for the Temerity area to open. They discussed how snowpack conditions varied as they skied different aspects and slope angles. They saw a large avalanche skier's left of Green Trees that released as a smaller avalanche near the ridgeline, triggered by AHSP with explosives. This avalanche also triggered several smaller, sympathetic avalanches (Figures 1 and 7). Being very familiar with this terrain, they had seen avalanches on this particular slope many times in the past, and did not think this avalanche was pertinent to their trip plan for the day, which included avoiding this specific terrain feature.
Once the Temerity area opened, Skiers 1 and 2 exited the ski area through a backcountry access point and descended Green Trees. They crossed the avalanche debris from the explosive-triggered and sympathetic avalanches. They continued downhill to a bench where they transitioned into uphill travel mode. From here, they worked their way up a sparsely treed rib to the rock outcrop where they planned to stop. Skier 1 later reported about 16 inches of storm snow in the area, but relatively shallow ski penetration.
Once they reached the rock outcrop at about 11,075 feet, Skier 2 suggested they continue two hundred vertical feet further uphill to a small stand of mature trees. Skier 1 later reported feeling “a weak layer” under the new snow as they climbed higher that he had not noticed lower. Their concerns about being on the slope grew. The pair did not want to transition to downhill travel mode in the middle of the slope, so they discussed their options, including continuing to the trees or crossing climber’s right to a prominent rock. Skier 1 was in the lead and continued climbing, so that they could glide slightly downhill across the slope to this rock.
At about 2:22 PM, the two skiers heard and felt a collapse. Skier 2 yelled, "We're going for a ride!" Skier 1 looked up and saw the avalanche breaking between him and the stand of trees. The slide swept both skiers down the slope on the skier's left side of the rock outcrop and into sparse trees. Skier 2 stopped at a large tree shortly below the outcrop. Skier 1 continued about 200 feet further down slope, coming to a rest on the snow surface with both skis still attached to his boots.
Members of the Aspen Highlands Ski Patrol (AHSP) at the Loge Peak station had seen the backcountry party climbing up Maroon Bowl and witnessed the accident. They immediately called 911. AHSP and the ski area Mountain Manager, one of two Mountain Rescue Aspen (MRA) rescue leaders on call that day, decided it was too dangerous to respond to the accident scene because of the unusual conditions, the large start zones above the route to the accident site, and the snow that had not avalanched above the site itself.
Skier 1 immediately texted his wife, at 2:29 PM according to his phone logs. He then turned his beacon to search mode and searched up the slope, but stopped below an island of trees when the number on his transceiver was 60 meters. He moved downslope and got lower numbers. He found Skier 2's ski poles, then a ski. The clues, along with a long tongue of debris, led him to believe Skier 2 was below him, so he began searching downhill.
Highlands patrollers watched the Skier 1 moving on the debris. They could also see Skier 2 on the snow surface above a tree. They were able to make voice contact with Skier 1. They instructed him to go uphill. Skier 1 pointed uphill with a ski pole, patrollers replied with a shouted "Yes!", and Skier 1 climbed uphill to the island of trees. He spotted Skier 2 and put away his beacon. Skier 1 reached Skier's 2 position by 3:10 PM.
When Skier 1 reached Skier 2, he was lying across the slope, head to the west, with the front side of his torso against a tree. Skier 2 showed no obvious signs of life. By this point, Skier 1 (a former member of MRA) was in cell contact with MRA's command office. After a short discussion, Skier 1 attempted CPR but found it ineffective due to Skier 2's injuries. Skier 2, a current member of MRA, was carrying his rescue-group radio. Skier 1 found the radio in Skier 2's pack, and began communicating with MRA directly via radio instead of cell phone.
MRA worked on getting a helicopter to the accident site to extricate Skier 1 and possibly Skier 2. HAATS (High-Altitude Army National Guard Aviation Training Site) accepted the mission, but eventually MRA decided weather conditions were not favorable. An hour or more after the accident, they instructed Skier 1 to ski out the basin down to the Maroon Creek road. MRA dispatched a team to improve a log bridge across the creek and meet Skier 1. The owner of the T Lazy 7 Ranch and Skier 1's wife had already driven up the road; they watched Skier 1 descend, then drove him to Aspen Valley Hospital, where he was assessed, treated, and released that evening.
The Pitkin County Sheriff's Office made the decision not to recover Skier 2's body that evening or the next day due to lingering avalanche danger. On the morning of April 10, HAATS flew MRA into the site, with MRA spotters on the ridge, uphill of the Loge Peak patrol station. They hoisted two MRA members onto the debris field. They were able to retrieve Skier 2's body and the HAATS helicopter flew the rescuers and Skier 1 out.
The forecast backcountry avalanche danger on the day of the accident was High (level 4 of 5) and there was an Avalanche Warning in effect for the CAIC's Aspen zone. Skiers 1 and 2 did not discuss the forecast or warning; Skier 1 had not read it and it is unknown whether Skier 2 saw it. They were aware of and discussed the unusually warm and wet storm. Then decided to enter complex avalanche terrain as the storm was ending.
The two skiers determined that the fresh avalanches on adjacent slopes were not pertinent to their planned route, having seen similar avalanches many times on those same slopes in the past. They traveled without incident until they made an impromptu decision to continue up a slope steeper than 35 degrees with a terrain trap (trees) below them. As they climbed, they noted that conditions on that slope were different than on the slopes below, though by that point they had few options for escaping the danger.
The sequence of decisions in this accident suggests more general insights that might help others avoid similar accidents. Terrain familiarity can make it difficult to recognize when conditions are different from those previously experienced. Fresh avalanches on adjacent slopes are clear signs of instability. A perception of scarcity - closing day at the ski area and fresh snow - can make it harder to step back from danger. Deviating from a plan in the field often leads to increased exposure to the hazard.
It is notable that snow safety personnel were also concerned about snow conditions that day. The AHSP did not open the Highland Bowl on the day of the accident for the first time since it opened for the 2017-18 ski season. After the accident, professional ski patrollers and search and rescue members made the difficult decision not to travel to and enter the accident site because of the level of and exposure to avalanche hazard.
Figure 8: Snow profile observed the day after the accident (April 9, 2018) on a north-northwest facing slope at 11,580 feet, adjacent to Green Trees in Maroon Bowl.
Figure 9: Snow profile observed at the top of the start zone a week prior to the accident (April 1, 2018).