Two ski patrollers were caught in an avalanche Friday after heavy snowfall from a recent atmospheric river triggered a slide on Lincoln Mountain in California’s Sierra Nevada.

Ski patrollers from mountain resorts in California, Nevada, and Colorado are at Mammoth Mountain in the Eastern Sierras, helping to provide safety following an avalanche that caught two patrollers and left one critically injured.

Mammoth Mountain officials said the slide occurred during avalanche mitigation work following a significant Sierra Nevada snowstorm, during which about six feet of snow fell in 36 hours.