When winter storms frost the mountains to the west of Las Vegas, hordes of visitors head for the high country in search of snowy adventures. Following Christmas, visitors don bright new mufflers and gloves, load sleds or toboggans in the car and eagerly aim for the alpine wonderland. The only place in Southern Nevada with enough snow, the Spring Mountains National Recreation Area, part of Humboldt-Toiyabe National Forest, offers a variety of winter activities.