05/01/2013 01:08 pm ET Updated May 01, 2013

Vail Pass Avalanche: Report Sheds More Light On Details Of Avalanche Tragedy

From The Vail Business Journal's Troy Hooper.

As a snowboarder prepared to huck a big rock south of Vail Pass on April 18, the snow beneath him gave way. He launched off the rock anyway and when he landed he remembers the snow "looking like an ocean" all around him.

The force of the avalanche knocked him down. He fought to stand up, trying to keep his board on the snow's surface. The man tried to gain speed to outrace the fast-moving slide that had ensnared him from behind. But he couldn't ride any faster than the debris. The slide slowed when it hit a bench on the mountain and it released him into the trees below. He somehow was able to ride to the bottom of the slide, and live to tell about it.

This is, in part, the account given in the Colorado Avalanche Information Center's final report on the recent Vail Pass tragedy that forecaster Tim Brown published on Tuesday.

Westminster resident Mark McCarron wasn't as lucky as his friend.

Whereas his friend had entered an area of Ptarmigan Hill — locals call it Avalanche Bowl — from the west, McCarron entered the terrain from the east. When the slide released on a north-facing slope, it is unclear exactly where McCarron was but the avalanche carried him into a stand of trees. He would be found on top of the snow's surface, resting against an 8-inch-thick tree, with several broken trees across his back.

McCarron had suffered significant trauma. His friends could not resuscitate him.

"This avalanche reminds us that even if you remain on the surface, getting carried into the trees can have fatal consequences," Brown wrote, noting it slid at about 11,900 feet in elevation and on a 35-degree slope.

The slide ran approximately 2,400 linear feet and 900 vertical feet. Its crown face was 850 feet wide and ranged in depth from three to 12 feet thick. The debris covered approximately 10 acres.

The report said that McCarron, 38, and a friend met in the parking lot at Vail Pass a little after 9 a.m. and motored their sleds 4 miles into the backcountry. They took turns shuttling one another to the top of Ptarmigan Hill on a snowmobile, in an area called Cupcakes, before meeting a third friend at 11 a.m. The group made multiple laps in Avalanche Bowl, avoiding a large cornice at its top and instead entering the bowl from the east and west sides. Other groups were also riding in Avalanche Bowl.

There had been harbingers of the tragedy that unfolded that day.

There was a weak snow layer that had been lurking in Colorado's high country since the fall. The Colorado Avalanche Information Center's forecast for that area that day warned that "deep persistent slabs are still a lingering concern" and that newly fallen snow that week raised the risk that the buried weak layer could fracture. The forecast noted two large slides fewer than 20 miles away broke a week earlier.

Still, the riders in the group were all very familiar with the area, experienced in the backcountry and they were carrying the necessary safety equipment, according to the Eagle County Sheriff's Office.

"Deep slab avalanches are difficult to forecast and manage," Brown concluded in his report. "When dealing with them, we should expect the unexpected. These riders and many others rode this terrain countless times without incident before the fatal avalanche. Deep slabs are often triggered from areas where the snow is shallow and weak. It is difficult for us to affect weak layers when they are under thick, hard slabs, but the cracks we start in thin areas can propagate into deeper snow, producing very large avalanches. Shallow areas are often difficult to recognize. Monitoring avalanche trends in surrounding areas can be effective ways to help anticipate these types of events. When faced with uncertainty, make conservative decisions."

Tragically, two days later, a group of five backcountry experts were killed in a similar avalanche on Loveland Pass. It was the deadliest slide in Colorado since seven people in Twin Lakes died in 1962.