The snow burst through the trees with no warning but a last-second whoosh of sound, a two-story wall of white and Chris Rudolph’s piercing cry: “Avalanche! Elyse!” The very thing the 16 skiers and snowboarders had sought — fresh, soft snow — instantly became the enemy. Somewhere above, a pristine meadow cracked in the shape of a lightning bolt, slicing a slab nearly 200 feet across and 3 feet deep