The Colorado Avalanche Information Center is urging backcountry enthusiasts to use caution in the aftermath of four avalanche deaths so far this winter in Colorado.
The third and fourth fatalities — a snowmobiler near Kebler Pass and a skier near Keystone — were reported Monday. The snowmobiler was buried when an avalanche broke west of Crested Butte. The slide, which was about 600 feet wide, 3 feet deep and 750 vertical feet long, also partially buried a second snowmobiler, who survived.
Monday’s second fatal avalanche, which was about 150 feet wide, 4 feet deep and 2,000 vertical feet long, was reported in the backcountry south of the Keystone Ski Area. Two skiers were caught in the slide.
On Wednesday, the Avalanche Information Center issued a special avalanche advisory that stated, “Veteran snow professionals are reporting triggered avalanches in well-documented avalanche paths that are breaking mature timber and behaving in surprising ways.”
In his daily forecast, Blase Reardon stated that there is considerable danger at, near and above treeline. Because of the potential for slides to break across terrain features and the massive amounts of snow that will be involved in any triggered slide, there is almost no margin for error, he said.
“You have almost no chance of skiing or riding out of a triggered slide,” Reardon wrote. “If you travel into the backcounty or leave a ski-area boundary today, the only terrain appropriate for these conditions are slopes less than 35 degrees that are not in the tracks or runouts of steeper slopes above.”
On Monday, the area also saw a widespread natural avalanche cycle, which included two slides in Marble and one in Express Creek. Two of those had a destructive size of D3, which could destroy a car or a wood-frame house, according to the Avalanche Information Center. The other carried a size of D2.5.
Many of the recent natural avalanches broke on old faceted layers that formed in early January and are now buried 3 to 5 feet deep beneath a well-consolidated slab. Below treeline, many of the crowns extend across terrain features in steep, treed terrain, according to Reardon’s report.
“Be very careful in your terrain selection; you can remotely trigger slides from thinner patches near the edges or bottoms of slabs,” he wrote. “On slopes with shallow snowpacks, avalanches could break at or near the ground. These conditions are more common on the eastern side of the zone.”