A Powell High School sophomore was critically injured Wednesday when she struck a tree while snowboarding at Red Lodge Mountain Resort.

Brooke Nisley, 16, was volunteering through the Eagle Mount program to assist young skiers with disabilities during the Wednesday trip. At the end of the day, she was returning from the slopes on a final run when the accident happened.

Nisley’s liver and kidneys were damaged, and she broke a vertebra in her back.

Nisley underwent an extensive surgery at Billings Clinic on Monday.

She was wearing a helmet at the time of the collision, and it likely saved her life.

Powell High School principal Bill Schwan said the activity Nisley was helping with was not a school-sponsored trip, but he had been to Billings to visit her in the intensive care unit. She remained in intensive care Monday, but “improvement (in her condition) is on the horizon,” he said.

Nisley is the daughter of Bruce and Sonja Nisley of Powell.

Nisley ran on the Panthers’ state championship cross country team last fall, finishing 15th overall. It was her second top-20 finish in as many years at the 3A championships. Nisley also was a member of the Panthers’ state-champion 4x800 relay team as a freshman and placed sixth in the open 1600 at last year’s state track meet.

She competed earlier this year as one of several Panther athletes participating in indoor track via an agreement with Cody High School.