The backcountry ski trip hit by avalanche was led by an outfit offering mountain adventures globally

The group of 15 backcountry skiers headed out on a three-day trek organized by Blackbird Mountain Guides into pristine wilderness near Frog Lake in California’s Sierra Nevada as a powerful winter storm moved into the state.

The skiers made their way Sunday to remote huts situated at 7,600 feet (3,415 meters) in Tahoe National Forest, carrying their own food and supplies. At 6:49 a.m. that same morning, the Sierra Avalanche Center had issued an avalanche watch for the area, indicating large slides were likely in the next 24 to 48 hours.

Around 5 a.m. Tuesday, the morning the group was scheduled to make its way back out to the trailhead, the center increased the watch to a warning. Within hours an avalanche hit near Castle Peak, trapping the skiers. Authorities said Wednesday that eight people were killed and one person remained missing. Six skiers were rescued after sheltering in place for hours as searchers battled blizzard conditions.

Nevada County Sheriff Shannan Moon said investigators were examining the decision to proceed with the trip Sunday despite forecasts of a major storm. It’s n...