Nothing about a winter at the local ski hill has prepared me for the gut-twisting prospect of launching into thin air off a ridge in Idaho's Sawtooth Mountains. "Ridge" doesn't even do it justice—it's more like the cutting edge of a granite ax. As we nervously remove gear from our packs, Clark Corey, our guide, nods at the exposed face plummeting away behind us and says, "Don't drop anything down there or it's going 3,000 feet." Anxiety drowns our chuckles. Skiing that face would actually be the easy way down. Instead, I've climbed here with four other skiers and snowboarders to descend a couloir called Resurrection, a snow gully that plunges like an elevator shaft between rock cliffs. Couloirs are prized by ski mountaineers, and until three days ago I'd never skied one. In fact, this thin sliver of snow is worlds steeper than anything I've ever skied before, and falling here would mean a long and violent tumble. Which, it turns out, is precisely where I'm headed.