A 14-year-old girl snowboarding in Westford’s Nashoba Valley Ski Area was taken by medical helicopter to Boston Children’s Hospital this morning after she was found unconscious following a jump, according to a manager at the resort. Al Fletcher, general manager of Nashoba Valley, said the girl was snowboarding around 11:30 a.m. in the Terrain Park area of the resort when she went over a jump, and the ski patrol found her unconscious. The teen, accompanied by her mother, was flown to Boston Children’s Hospital and had not regained consciousness by the time she left the ski area, Fletcher said. Westford Police and Fire departments had no further information on the incident or on the girl’s condition. The Terrain Park area, a part of a ski resort typically used for tricks, has numerous jibs, rails, and jumps for use by skiiers and snowboarders.