"It's the snow, stupid," joked Susie Barnett-Bushong, marketing director for Grand Targhee resort in Wyoming. "There's a magic number when they will drop everything and come up. It's usually 10 to 12 inches" of new snow.
"We've tried a million different things," Barnett-Bushong said, including — in years' past — eyeballing whether a snowy mound reached a basketball hoop 10 feet above ground.
These days, Grand Targhee, like many resorts, uses sonar and other devices to gauge recent snowfall, settled depth (also called "base") and the season's snow total.
But even with this science, daily snow statistics on resort websites sometimes hardly resemble what skiers find on the slopes. The reality can be a joyful surprise or a cold shock.
Many factors, natural and artificial, may cause this discrepancy: where and how snowfall is recorded, wind, sunshine, skier traffic and how much time has passed since the measurement was taken.
Disappointed visitors may suspect deception. But resorts deny that they deliberately inflate snow figures.
"There is no fabrication of snow reporting here," said Anna Olson, spokeswoman for Jackson Hole Mountain Resort, about 45 miles from Grand Targhee. "We have a reputation, if anything, for underreporting."
Tom Cottrill, president of SnoCountry Mountain Reports, a nonprofit trade association based in Lebanon, N.H., thinks most resorts try to get accurate numbers.
"The worst thing a ski area can do is oversell its snowfall or its amenities," which angers customers, said Cottrill, whose group supplies statistics on ski conditions from hundreds of resorts to Associated Press and other media.
Jim Woodmencey, a private meteorologist who works for radio stations in Jackson Hole, Wyo., is more skeptical.
He thinks some ski areas may round statistics upward or place gauges in especially snowy areas. But, he added, "I don't think they out-and-out lie to you."
But they do all measure differently, Cottrill said. Here's a closer look at the vagaries of snow reporting:
Where: The most accurate spot for a snow gauge is right on a ski trail, but for obvious reasons, that can't be done. Anywhere else is a compromise.
"Mountains have micro-mini weather systems," said Jackson Hole's Olson. Snow accumulation can vary wildly by elevation, wind direction and terrain.
A popular place for gauges is in a wide clearing within a wooded area off a ski run. Trees here block the wind, so the flakes are more likely to fall straight down. The problem is that ski runs aren't shielded this way, so snow may blow away or drift.
At Mammoth Mountain in California, snowfall is measured near the main lodge, at about 9,000 feet, far below the level where most skiers and snowboarders start down the trails.
Less snow falls at 9,000 feet, but less blows away than on higher terrain, which is above the tree line, said Walter Rosenthal, the resort's snow and avalanche analyst.