EVOLENE, Switzerland — A skier was buried beneath an avalanche for 17 hours in the Swiss Alps before being pulled from the snow with only mild hypothermia, police said Sunday. The 21-year-old man appeared to have survived because he was trapped next to a pocket of air that allowed him to breathe even though he was unable to free himself from the crushing weight of the snow, police in the southern canton of Valais said. "I've never heard of such a case before," said police spokesman Jean-Marie Bornet.