Before winter fades . . . Outdoors in the snow; The New Complete Snow Camper's Guide, by Raymond Bridge. New York: Harper & Row. 335 pp. $15. Backcountry Skiing, by Lito Tejada-Flores. San Francisco: Sierra Club Books. 320 pp. $8.95 (paperback).

March 10, 1982

Why would anyone want to go camping in the middle of winter with three feet of snow covering everything? To begin with, it's cold, and the nights are long, just imagine 12 to 14 hours in a sleeping bag. Why bother? On the other hand, maybe you enjoy winter and the outdoors as many of us do. Snowshoeing or skiing might be your favorite hobby. But you still aren't sure you'd like camping overnight in zero-degree weather.

Raymond Bridge has put this text together to help you get started - safely - in winter camping. Being safe is the key, because a mix-up in the summer might lead to an uncomfortable chilly night out on the trail, but in the winter it could be almost your last night.

Fundamentals such as clothing, equipment, planning, camping techniques, route finding, weather, and avalanche, which the novice needs to know, are covered. Since the beginner isn't ready for advanced techniques used in high mountain skiing and climbing, these discussions are left out. A helpful appendix includes sections on how to make your own equipment, selected readings on winter camping; and checklists for day or overnight trips.

The guide contains a mountain of information. It's too heavy to pack on your back but just right for reading and dreaming about next to a warm, cozy fire.

''Backcountry Skiing'' is a book for the serious skier - alpine or nordic, beginner or expert - who wants to head away from the chairlifts and groomed trails into untracked territory.

This updated version of the author's ''Wilderness Skiing'' (published in 1972 with co-author Allen Steck) gives advice on the latest equipment and techniques. The opening section compares types and brands of skis and other equipment, explaining what to look for in a boot, a binding, or pair of poles. Other chapters cover snow structure, avalanches, winter camping, first aid, and evacuation. More than half the book is devoted to technique, from basic stride to advanced turns. This lightweight paperback will slide handily into a backpack.