They spotted the enemy, huge and menacing, on the first reconnaissance sweep of the morning. The patrol decided to launch an immediate strike and eliminate the threat. There was no need for howitzers or the 105 mm recoilless rifle. A simple bombing run would do the job.

One patrol member trekked high above the danger zone and lobbed in a two-pound "hand bomb," or explosive charge. There was a muffled explosion and then a deep, prolonged roar as an enormous wall of snow rumbled harmlessly down the hillside into the empty valley below.

It was just one more skirmish in the endless war of man versus avalanche -- a struggle that becomes a major regional concern each year from November to May in the steep, snowy reaches of the Rocky Mountain West.

This year, the anti-avalanche campaign has been unusually hectic because the Weird Winter of '86 -- marked by long stretches of warm, spring-like weather interrupted now and then by ferocious storms -- has spawned more avalanches than the region has seen in decades.

"Both in number and in the enormity of the things, we're getting reports of a big jump in avalanches all the way from Idaho to New Mexico," said Hank Deutsch of the U.S. Forest Service office in Denver. "This could be the worst year in a long, long time."

The number of snowslides began snowballing last fall, when the intermontane states received unusually heavy accumulations in October and November. But the major impetus was the intense nine-day storm that ravaged the West in late February.

In the low country, such as the California grape fields, those big storms caused floods and mud slides. Here in the mountains -- where some local weather stations reported up to 90 inches of snowfall in nine days -- the storms led to an unprecedented avalanche of avalanches.

Colorado, with a higher average elevation than any other state, is the nation's No. 1 avalanche locale. During this year's late February blitz, the state had about 750 slides -- roughly 40 percent of the average annual avalanche total here. Utah reported 1,000 avalanches, about half its normal annual total, in the same nine-day period.

The February slides killed at least three people -- two downhill skiers and one ski tourer -- and left others trapped in snow for periods from five minutes to five days.

Compared to other sudden killers, such as murder or auto accidents, avalanches are a statistically minor public threat: nationally, the slides take about a dozen lives per year, nearly all in the mountain West.

But because the threat of damage is great -- some European avalanches reportedly have killed 2,000 in one swoop -- and because uncontrolled avalanche danger could have a chilling effect on transit and on the region's booming winter sports industry, all western states mount costly, sophisticated avalanche-control operations each winter.

The task is a shared public and private concern; federal land management agencies (the park and forest services and the Bureau of Land Management, for example), state highway departments, railroads and ski resorts work together to spot impending slides and neutralize them before they cause danger.

Avalanche prediction is a complex mixture of science and intuition. The trick of spotting a potential snowslide before it falls is based on the relatively new academic discipline of "snow physics," which involves studying crystalline structures and temperature gradients in the snow pack.

Every morning, all over the West, avalanche patrol teams like the one here at the Snowmass Ski Resort just south of Aspen ski or trek through the mountains monitoring snow conditions and searching for hillsides that might let loose if the packed snow is triggered by a hiker or skier, an animal, the roar of a passing airplane or even a gust of wind.

"I try to go out real early each morning and dig some pits [in the snow]," said Darrell Rankin, a lanky, ruddy-faced avalanche technician who has been on the Snowmass patrol for 11 winters.

"What I do is a lot like a geologist. I look at the different strata [layers] of snow and try to see how the crystal structure differs from one to the next. And depending on which layers are on top of which other ones, you can predict that this hill, or another one with the same conditions, is maybe going to slide."

Once a potential slide is spotted, the standard tactic is to turn a potential avalanche into a real one: that is, to set off the snowslide under controlled conditions after the area has been evacuated.

The western avalanche hunters use a wide variety of weaponry -- in the literal sense. Some patrol teams shoot big Army recoilless rifles or howitzers; at many resorts, the booming echo of artillery fire is a common backdrop to a day on the slopes.

Here at Snowmass, Rankin's preferred weapon is a "hand bomb" -- a lethal-looking device reminiscent of a particularly potent Roman candle. Rankin skies to a spot above the avalanche wall, drops his "hand bomb" with a delayed charge and waits for the explosion to loosen the snow pack and trigger a slide.

For the most part, these "controlled" avalanches remain under control. But not always.

Last month, an avalanche team near Frisco, Colo., inadvertently blocked all four lanes of Interstate 70 when a manmade avalanche loosened more snow than expected. Under such controlled circumstances, no one was hurt, but the same slide, occurring naturally, could have been a disaster.

As last month's deaths indicate, not every avalanche can be predicted and neutralized. Patrol teams have detailed drills for finding victims, often buried beneath four feet of snow or more. The search team here includes two hardy yellow Labradors, Kachina and Chopper, who can pick up a human scent through 10 feet of snow, Rankin said.

Avalanche hunters warn skiers and back-country hikers that most avalanches come in windy weather within 24 hours of a snowfall.

If you see or hear an oncoming avalanche, experts advise removing skis and other gear. Avalanche survivors say the best tack is to try to swim backstroke to keep atop the billowing waves of snow.

A person buried in snow should try to clear an air pocket and try to poke something -- an arm, a ski pole, whatever -- above the surface to alert searchers who otherwise see only a vast field of lumpy snow.