Snowbird, UT – The snow safety department of Utah’s Snowbird Ski Resort has issued a report detailing the events surrounding a deadly in-bounds avalanche on Sunday, Dec. 14 that killed 27-year old Heather Gross of Salt Lake City.
The report, filed with the Utah Avalanche Center by Jim Collinson of the Snowbird Snow Safety Department, confirms that explosives were used the morning of Dec. 14 to mitigate the avalanche danger in the very spot where the avalanche occurred. Hundreds of skiers and snowboarders skied the area before the slide released at approximately 12:24 p.m.
The avalanche was triggered by an unidentified male snowboarder on the High Baldy Traverse on the northwest face of 11,068-foot Mount Baldy. The fracture line bisected the traverse, sending a wall of snow down the slope and burying Gross under three feet of snow for nearly an hour. The victim was found by a probe team and evacuated to University Hospital in Salt Lake City, where she died later that afternoon.
The incident occurred on the first day this ski season that High Baldy was open to the public. The Snowbird Ski Patrol had conducted extensive avalanche control efforts prior to opening, including a 105 mm rifle bullet on November 20th, two pounds of high explosive on December 9th, and two separate two-pound shots of high explosive on the morning of the deadly avalanche — one in the starting zone of the subsequent avalanche, the other on the lower flank of the subsequent avalanche, all with no results. All five of the Baldy routes covering West Baldy, Northwest Baldy, and the western exposure of the Peruvian Ridge were run by Snowbird Ski Patrol on the morning of Dec. 14, when 55 starting zones were tested with explosives or skis with no significant results. Access to Mt. Baldy was therefore opened at 9:28 a.m. that morning.
Following the report of the avalanche to Snowbird Ski Patrol by a witness using a cell phone, a rescue team including trained avalanche rescue dogs, avalanche transceivers and Recco receivers was dispatched to the accident scene. Collinson’s report indicates that the dogs had difficulty locating the scent of the victim due to the large number of rescuers on the scene. The victim, who was not wearing an avalanche beacon or Recco system, was located 58 minutes later.
The slope that failed faces northwest, and began at an elevation of 10,470 feet. It has a slope angle of 36 degrees. The initial release was one foot deep and 35 feet wide, but as it traveled down the slope it released the skier’s left flank and reached a maximum width of 120 feet. The average depth of the crown face was one foot, with pockets of up to three feet. As the avalanche descended, it gouged into old faceted snow and entrained much of the snow in the track. The avalanche ran for 1,000 vertical feet, resulting in a debris field up to 10 feet deep.
After receiving a record amount of precipitation in the form of both rain and snow in early November, the Wasatch Mountains were under high pressure until the end of November, developing a very faceted snowpack. On November 28th a significant rime and rain event occurred that reached even the highest peaks. Weather in early December returned to high pressure with cold temperatures, further deteriorating the snowpack above and below the rime event. December 8th broke the high pressure spell with a storm which deposited a foot of 6% snow. The night of December 12th had strong southwest winds, resulting in a wind slab on the surface, and was followed on December 13th with a storm depositing 17 inches of 6% snow.