O n the morning of the deadliest avalanche in California’s modern history, Cody Townsend was skiing above the west shore of Lake Tahoe. People like him, who live for untracked expanses of wilderness snow, had found little to celebrate this season. Across much of the American West, the temperatures had been high, and the hills bare and brown. According to the Central Sierra Snow Lab, operating from a cabin nearby, accumulation had been running seven feet below normal. But now snow was dumping.