The New Science of Snowmaking
Credit: Photograph by Cody Doucette

It's every ski town's worst nightmare: a winter with no snow. Locals start burning old skis and shaving their heads, businesses suffer, people get grumpy. For much of this ski season, that's been the reality across the United States. As of mid-January, there was no significant snow anywhere in the Lower 48. Squaw Valley, California, a Tahoe resort that routinely measures snowfall from a single storm in multiple feet, had a grand total of 12 inches at its base, while the upper part of the mountain had zero; fewer than 200 of its 4,000 total acres were open. Stratton Mountain in Vermont was doing slightly better with around 30 inches at its base and 395 of its 600 acres open. Smaller resorts like Bogus Basin, outside of Boise, Idaho, had yet to open at all.

Global warming and the climate debate aside, the cruel truth is that winter storms – and the precious snow they deliver – are fickle beasts. Sometimes they just don't show up to the party. In this case, any open resort is completely reliant on one thing: its ability to make snow.

That might explain why one resort in particular has been flourishing during this ultralean snow year: Sun Valley, Idaho. A long series of cold, clear days combined with a multimillion-dollar, state-of-the-art snowmaking operation – the largest in North America – made January skiing at Sun Valley's Bald Mountain as good as ever, with more than 90 percent of marked runs open.

The kicker is that these runs weren't just open. Thanks to new computer software and advances in snowmaking technology, the snow quality was unbelievably good.

The cost and energy consumption of snowmaking are considerable. Sun Valley spent $15 million installing its snowmaking system in 1991, and since then has continued to invest in new, more energy-efficient equipment. But the sizable investment pays off during low-snow seasons like this one: Sun Valley's revenue is almost even with what it was this time last year, when natural snow was plentiful. Squaw Valley, which suffered its second-driest December in 100 years, refuses to comment on its income this winter, but considering that the lucrative holiday season came and went without snow, it's reasonable to assume it was abysmal.

Man-made snow is referred to as "product" and is analyzed, discussed, and critiqued like the finest Colombian marching powder. Creating high-quality snow is equal parts science and art. It requires a dedicated staff of skilled mechanics and experienced groomers, along with sophisticated equipment and a cooperative climate: cold and dry, with low humidity. Other than that, it's just a matter of combining compressed air and water in the proper proportions.

"It all starts with the wet-bulb temperature, a mathematical correlation between the air temperature relative to the amount of humidity – kind of like windchill," Corey Allen tells me as we stand outside one of Sun Valley's five machine rooms dedicated entirely to snowmaking. An Australian snowboarder who came to Sun Valley 15 years ago on a working holiday, Allen ended up getting a night job making snow so he could ride all day. He's now one of the head operators in the snowmaking department and an absolute fanatic about cultivating the perfect product. "Depending on the type and quality of snow desired," he shouts over the roar of three 1,100-horsepower air compressors housed beyond the thick doors separating us from the control center, "wet-bulb temperature dictates how much air pressure and water are needed."

Inside, we walk along a raised grate that sits above a large water tank. Three computer monitors sit on a desk. On the first screen is an interactive trail map with blue boxes indicating each snow gun and red lines representing the pipes that link them. Weather monitors are also visible, along with highlighted wet-bulb temps and wind direction. Boxes change shape to let the operator know which guns are running, which are ready to go, and which have just finished. When weather stats are highlighted white, it signifies optimum snowmaking conditions. The operator clicks a button, and air and water from the holding tank are pumped through the pipes; minutes later, snow erupts from the chosen guns.

The second screen lets the operator keep an eye on all five machine rooms and alerts him to pump or compressor problems. The third screen shows the hard data, which is read and interpreted by a specialized software program that creates the displays on the other two screens. With this interactive system, Sun Valley can make snow 24 hours a day.

There are two types of desired snow. The first is called "production snow," a denser flake made with more moisture. Often as hard as rock after it settles, it serves as the base for ski runs and is sculpted into halfpipes and kickers for terrain parks. The second type is called "dress snow" and is much harder to make. Nicknamed "gunpowder" by locals, it feels like satin under your skis and, groomed correctly, produces the corduroy surface for which Sun Valley is famous. (Whenever new guns are turned on, a snowmaking operator tests the product by making a snowball. Production snow will ball easily and won't yield water when squeezed. Dress snow is too powdery to form a ball.) This buttery-­smooth condition is becoming the snow of choice for a skiing demographic that is growing older, because it offers a much lower-impact ski experience. At any age, if you like skiing fast, there's nothing better.

Compressed air and water explode from two gun nozzles, each about as wide as a pinky finger (5/8 inch) and located at the end of a 10- to 12-foot standpipe. The cloud of snow blows up to 50 feet high, as 125 pounds per square inch of air pressure collide with 28 gallons of water a minute in a hissing roar. There are 555 such guns on Sun Valley's Bald Mountain, covered in yellow pads and lining the ski runs like giraffes. The 110 weather monitors placed all over the mountain read temperature, humidity, and wind direction every six minutes, allowing the guns to automatically adapt their mix to changing elements. "This gives the product greater consistency from the top of the mountain to the bottom, because the temperature and humidity can vary greatly," Allen explains. "We lay down the product," he adds proudly, "and our groomers polish it to perfection."