Bryce Mountain ski area in western Virginia is open for skiing about 100 days a year. If it weren't for snowmaking, the area would not be open two weeks.

"We make snow every time the weather is cold enough," said area manager Manfred Locher. "We like to make snow 24 hours a day if we can. Then, if we get a warm spell, our base is deep enough to keep us going."

Bryce currently has between 20 and 60 inches of snow on its nearly two miles of slopes, enough -- according to Locher -- to keep the area open even with a week of warm, rainy weather.

That is why Bryce Mountain doesn't mind spending $500 an hour to make snow.

Man-made snow: it used to be called artificial snow until skiers realized that it is not important who makes it, as long as it is snow. In fact, man-made snow is not like the stuff Mother Nature throws together in her celestial kitchen. Her snow is lighter, and comes in all those different hexagonal designs. Man-made snow, even the lightest of it, is heavier, as though dosed with preservatives and artificial flavorings and colorings. It doesn't even have the same pretty shape. It is more like fine, soft hailstones.

But, like some heavily processed foods, man-made snow has an advantage over the real article. The biggest advantage is that it is available when natural snow is not. Another advantage is that it lasts longer.

Good snowmakers, often called mountain men, know how to adjust the mixture of water and compressed air that is forced through the hoses so as to make the first few inches of snow laid on a slope very heavy, very wet. It is the kind of material you hate to ski on: it is too heavy to make a turn in. But it produces a great base, the kind that lasts forever.

Then the mountain men let that cure. It takes some 24 hours for a five-inch cover to dry. On top of it they put some lighter snow, with more air in it, snow that is the man-made equivalent of powder. While man-made powder won't fly up around your face when you ski through it ankle deep, it does ski smoothly and easily, and --more important to the mountain men --the slope.

According to Marilyn Hertz, the ski school director and all-purpose enthusiast at Camelback in Pennsylvania's Poconos, grooming is the big ference. No matter how much snow is on the ground, or whether it is artificial or natural, it is only the top layer that counts for the skiers.

Grooming means getting out on the mountain just after a midnight ice storm and turning the inch-thick crud into granular snow by the time the first skier hits the slopes.

Grooming means taking the excess snow from the trails and piling it on the edges to save for a rainy day; taking the banked snow at the edges of the slopes and using it to cover the thin spots at the middle, and downside of the mogul (snow ridge) without ruining choice moguls. It also means keeping the beginner's slopes as flat as the contours of the land will allow.

Grooming is done with just a few instruments: a shovel for the tight spots, and a SnowCat -- a tractor out-fitted with special treads to help it climb mountains -- that pulls several specialized tools. Basically, there is a blade that shaves moguls and fills in holes, a chain mesh rug that breaks hardpack or packs powder, and a roller with spikes that is murder on ice.

The sophistication of snowmaking and grooming -- or snow farming, as aficionados call it -- does not end there. Camelback, like many other ski areas, subscribes to Accu-Weather, a private weather service keyed to the needs of the resorts. Accu-Weather, headquartered in State College, Pa., calls Camelback collect every day and predicts the temperature, humidity, wind velocity and other pertinent information for the next 24 hours -- hour by hour.

Snowmaking depends on more than just cold; the humidity must be low for the snow guns to be able to spew out something resembling snow. If the humidity is high, the 1,000/gallon/ minute water-use capacity at Bryce Mountain would simply deposit that much water on the slopes.

It is necessary, also, to limit snow-making to relatively windless times. Wind can lift the new snow from the slopes and deposit it in the woods.

At Camelback the mountain men check the Accu-Weather forecast before deciding whether and when to create. If the temperature is going to hover around 32 degrees all night, but the humidity won't drop to snow-making levels until 2 a.m., these artisans will go home and nap until 2 a.m., then get out their equipment. No use staying awake and on the payroll waiting for the barometer to change.

Hertz is a real snowmaking booster. She does not hold the belief that artificial snow is in any way inferior to nature's product.

"Out in the West, where they get that dry powder, there may be a difference," she offered. "But here in the Poconos what snow we get is usually heavy and wet. Compared to that, the snow we make is not artificial snow, it is just artificially made."