Detailed Accident Report
Submitted By: CAIC; Hunker, McCall, & Logan
Place: Sunshine Peak, 5 miles southeast of Aspen
Summary: 1 skier caught and carried. 2 split-boarders caught, buried, and killed.
***OFFICIAL REPORT FROM CAIC***
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Mount Shimer, southeast of Aspen
March 13, 2007
1 skier caught and carried. 2 split-boarders caught, buried, and killed
Three friends were on a backcountry ski vacation in the Aspen area. They chose an ascent of Mount Shimer for March 13. They were ascending a treed, north facing slope below point 12,088. At approximately 1:50 pm, the lead skier remotely triggered a large avalanche in the bowl to the east. Just after this, a smaller avalanche fractured above the party. The avalanche caught all three, but the upper skier was only carried for approximately 100 feet. The avalanche swept the two lower men on split boards down the slope and buried both. The victims were buried one above the other with about 100 feet between them. The skier found the upper victim first. After the skier dug the upper victim?s head out, he continued the search for the second buried man. Once the second buried man was uncovered, the rescuer retrieved a cell phone out of one of the victims? pack and made a call to 911. When Search and Rescue personnel arrived on scene, they determined that both buried victims were dead.
The red oval indicates the approximate location of the fatal avalanche. The remotely triggered avalanche was in the northwest bowl of Mount Shimer, near the "11800."
The accident site is between two weather stations. The Independence Pass SNOTEL site is 6.4 miles east of the accident site, on a southwest aspect at 10,600 feet. The Ajax weather station is 6.8 miles northwest of the site at 11,184 feet. Data from Ajax is provided by Aspen Skiing Company and Aspen Mountain Ski Patrol.
Three to five inches of snow fell during a brief storm on March 10. The Independence Pass SNOTEL site indicated about 2 inches of snow, with 0.2 inches of water equivalent. The Ajax weather station indicated about 4 inches of snow.
A high-pressure ridge started to build on March 11. At the Independence Pass SNOTEL site, daytime temperatures rose above 40 degrees F on March 11, and above 50 degrees F on March 12 and 13. There was an inversion the night of March 12, with cooler air in the valley floor. Overnight temperatures at the Ajax weather station did not drop below freezing. The inversion would not trigger an avalanche, but could make higher elevations more unstable than lower elevations. At the time of the accident, the temperature at Independence Pass SNOTEL was 48 degrees F, cooling from the afternoon high of 53 degrees F. The temperature at the Ajax weather station was 42 degrees F, the high temperature for the day.
Plot of the hourly temperature from the Independence Pass SNOTEL site. The temperature at the time of the accident (indicated in red) was 48 degrees F.
Plot of the hourly temperature from the Ajax weather site. The temperature at the time of the accident (indicated in red) was 42 degrees F. Low temperatures were above freezing the night of March 12.
Three friends were vacationing in the Aspen area. They were in their 30s, and former graduate students from the Colorado School of Mines. On Tuesday, March 13, they selected an ascent up to Mount Shimer, locally known as Sunshine Peak, from a guidebook (Lou Dawson, 2000, Colorado Backcountry Skiing). All three had avalanche transceivers, shovels, and probes. One man used alpine touring (AT) skis, while the other two used ?split? snowboards. On Monday, the three men checked the backcountry avalanche danger on the CAIC web site. They dug a snow pit before ascending the slope that eventually avalanched.
The group neared the ridge at approximately 1:50 pm. The skier lead the way, traversing the steep slope, with the other two ascending the switchbacks behind him. Near the top of ridge the lead man remotely triggered the larger avalanche to the east. Then the slope under the men fractured. The second avalanche caught all three. The avalanche only carried the skier for approximately 100 feet, but the two men on split boards were swept down the slope and buried.
Mount Shimer is locally known as Sunshine Peak, because it is one of the last sunlit peaks in the evening. The crown of the remotely triggered avalanche is visible on sunlit face. The fatal avalanche occurred on the treed ridge just in front.
A photo of the avalanches from below. The Flight For Life helicopter is flying over the larger avalanche.
A photo taken March 14 with the crown of the fatal avalanche in red. The extent of the remotely triggered is apparent.
The group triggered two avalanches on the slopes of Mt Shimer. The larger, remotely triggered avalanche ran in the northwest bowl of Mount Shimer. It was visible from the Aspen Mountain Ski area and the trailhead. It was a soft slab avalanche, remotely triggered by a skier from several hundred feet away, large relative to the path, capable of destroying a car and breaking trees, with a bed surface of old snow (SS-ASr-R4-D3-O). The crown was at approximately 12,000 feet on a northwest to north facing slope.
The second, smaller avalanche caught all three men. The second avalanche occurred on a north-facing slope at 11,800 feet. It fell 800 vertical feet through the trees. The crown was 165 feet wide and 2 to 2.5 feet deep. Slope angles at the start zone were approximately 38-40 degrees. The avalanche was a soft slab, skier triggered, large relative to the path, capable of burying and killing people, with old snow as the bed surface (SS-AS-R4.5-D2.5-O).
A crown profile at the accident site showed a total snowpack depth of approximately 5 feet (150 cm). The upper snowpack consisted of mostly rounded snow grains with an average Hand Hardness Index score of 1F. This upper snowpack was resting on a weak layer of 2 mm faceted crystals roughly 2.5 feet (75 cm) below the surface. This layer fractured and produced the avalanche. The lower snowpack and bed surface of the avalanche consisted of weak facets and depth hoar up to 3 mm in size. The crown of the avalanche at the profile site varied in depth from 2 to 2.5 feet (62-80 cm). Avalanches observed during the last week in the area had very similar depths at the crown.
Self-rescue is the best chance for a live recovery. These men were well prepared. After the flow of the avalanche passed the skier, he removed his skins, switched his avalanche transceiver to receive, and headed down the debris. The skier found the upper victim first. After uncovering his friend?s head, the skier continued to search for the second snowboarder. The victims were buried one above the other with about 100 feet between them. The upper burial was at 11,030 ft with the victim 7 feet (215 cm) below the surface. The lower burial was at 11,000 ft, with the victim 3.3 feet (100 cm) below the surface.
When the second victim was uncovered, the skier retrieved a cell phone from one of the victims? pack and called 911. The call occurred at 1500 hours. Approximately 1 hour elapsed between the avalanche and the 911 call. The Pitkin County Sheriff?s office mobilized Mountain Rescue Aspen and sent a hasty team into the field. A Flight for Life helicopter from Summit County flew to the scene with a medic and snow safety expert. Mountain Rescue transported the survivor and victims off the peak to waiting snowmobiles. They arrived in Aspen just before dark.
Looking up the fatal avalanche. The crown is just visible on the skyline. The burial locations are marked, the upper 7 foot deep burial in red, and the lower 3 foot deep burial in blue.
Both the Colorado Avalanche Information Center (CAIC) and the Roaring Fork Avalanche Center (RAFC) rated the backcountry avalanche danger as MODERATE on March 13. In the week prior to the accident, observers reported three other remotely triggered avalanches around the Aspen zone. These occurred near treeline on both northwest and northeast facing slopes. Forecasts from both the CAIC and the RFAC warned of some persistent weak layers and deep instabilities on steeper northwest, north, and northeast aspects near and above treeline.
The CAIC forecast for March 12 was valid through the afternoon of March 13. The danger was MODERATE on all aspects and elevations. The Snowpack Discussion concluded, ?though it feels like spring you still need to worry about deep slab avalanches. There have been both natural and remotely triggered slides in the last week. The most likely place to trigger a deep slab is an N-E facing slope that is near or above treeline and steeper than about 35 degrees.?
The Roaring Fork Avalanche Center issues forecasts in the morning. The forecast for March 13 was MODERATE above treeline, and on NW-N-NE aspects near and below treeline. The discussion warned backcountry travelers to ?be especially cautions on NW-NE slopes steeper than 30 degrees at and above treeline.? The problem was ?persistent deep instabilities? that can be found on many slopes. One layer, located roughly 60-90cm (2-3ft) from the top of the snowpack, has produced very clean test shears in our transitional snowpack. On NW-NE slopes at and above treeline, where the snow has been less affected by the warm temperatures, these instabilities will be more easily trigger.?
Rob Hunker (CAIC), Brian McCall (RFAC), Spencer Logan (CAIC)
March 14, 2007
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ASPEN - The Pitkin County Sheriff's Office says an avalanche killed two cross country skiers Tuesday afternoon.
The two victims were among three men who were cross country skiing five miles southeast of Aspen. The men were in an area where cross-country skiers and snowmobilers usually go, but it was not an official resort.
The avalanche buried the skiers around 2:15 p.m. on Mount Shimer. The mountain is also known as Sunshine Peak.
The avalanche started at 11,500 feet and swept down onto the skiers, who were 200 feet below.
One of the skiers was covered in 8 feet of snow.
Nineteen rescue workers took snowmobiles back to the avalanche and Flight for Life transported the dead skiers to the Aspen Valley Hospital where they're bodies were then turned over to the Pitkin County Coroner's Office.
The surviving skier, 33-year-old Jason Luck of Arvada, was rescued after he called rescuers from his cell phone.
Luck refused medical treatment when crews arrived.
The Pitkin County Coroner's Office will determine the exact cause of death.
The Colorado Avalanche Information Center maintains a map that details how high the avalanche danger is around the state.
Click here to see the map.
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