They were skiing low angle slopes presumably below treeline:
On March 5, Tollund’s new forecast warned guides of “considerable” to “high” avalanche danger above the treeline; of “moderate” danger below it; and it rendered “closed” all “runs as well as any traverses that travel under/across exposed start zones.”
But they failed to recognize that the slope they were going to ski was underneath another feature with a headwall steep enough to slide:
At around 9:30 a.m. on March 7, Hans, Spencer, Van Harte, and Ehren Samuelson, who was driving the cat, headed into the backcountry. According to the CAIC’s accident report, the guides communicated the risks to their group of highly skilled clients. “They knew the danger, and they wanted to go,” Spencer says. The guides skied with their clients in a way Spencer says was manageable even on that day. They stayed on low-angle slopes, “wiggle-butting” through the deep powder, and they did safety checks before they entered slightly steeper terrain. Nothing slid. Sometime after noon, they skied a run called the Funnel, and the snow was sublime. Then Hans, tempting fate, or perhaps failing to remember that it sat beneath a headwall steep enough to slide, suggested the group ski Bootpack, a run beneath Shipwreck, Spencer says. They all agreed. The guides and Hans had succumbed to what Dale Atkins calls “familiarity.”
Tragic.
The article also seems to suggest that cat skiing is the Wild West -- some operations with really stellar snow safety operations, others not so much. Caveat Emptor!
Mike