Want to know which mountain you need to ski today? ask Joel gratz, master of the high country’s fickle microclimate.

Back in late November of the 2015/16 winter season, after the first of a series of storms has dumped more early-season snow on Vail and Beaver Creek than anybody could remember, Joel Gratz settles onto a stool at Garfinkel’s and toasts a day that began with the opening of Chair 10—and first tracks through 18 inches of powder—and only got better.

Like most skiers and snowboarders on the mountain this day, Gratz is living the dream. Albeit a very particular dream.

“Most meteorologists know that’s what they want to be before the age of 10,” says Gratz, proprietor and chief weather guy at OpenSnow.com, the most-followed mountain-specific daily powder forecast in Colorado. “Something big happens, like a hurricane or a blizzard or a tornado. For me, it was just watching snow. I was a weather fanatic as a kid.”

Gratz learned to ski at Shawnee Mountain in the Poconos, raced at Tussey, and was on the ski team at Penn State, where he received an undergraduate degree in meteorology. After interning for TV meteorologists at Channel 10 in Philadelphia (“an exercise in what I didn’t want to do”), he moved to Boulder to further his skiing and schooling, earning a meteorology-focused environmental studies graduate degree. That led to his first real job, as an analyst forecasting hurricanes and tornadoes for a Boulder insurance company, one of those soul-crushing stretches in cubicle purgatory that can seem like a life sentence when when you’re a skier in your twenties and your world revolves around powder days.

In 2005, after he enjoyed a phenomenal session of floating the Back Bowls then skiing the Minturn Mile with Gary Gilman, the uncle of a college friend, Gilman studied the sky. “He asked, ‘So Joel, do you think tomorrow’s going to be a powder day?’” Gratz recalls. “I said, ‘Gary, I looked at my models. No, this storm’s done.’ He looked up at the clouds in kind of a folkloric way and said, ‘No, it’ll snow.’ ... I said, ‘You’re out of your mind, old man! I’m going home.’ And of course, as I drove over Vail Pass, it’s dumping.”

And that’s when Gratz had an epiphany.

“I thought, ‘I have a degree in meteorology. I shouldn’t miss powder days.’”

He started researching resort microclimates, weather patterns, and phenomena like orographic lift, when the prevailing wind hits a mountain, rises up over the peak, cools, and creates snow. Comparing weather data with topographic maps, Gratz noticed that west winds maximized orographic lift at Beaver Creek, while northwest winds did the same for Vail.

“After a storm, you can judge where you should ski based on the wind,” says Gratz. “With a northwest wind, Vail can double what Beaver Creek gets. But with a west wind, Beaver Creek might get 30 percent more snow than Vail.”

Like Craigslist founder Craig Newmark, Gratz started e-mailing a newsletter to friends in 2007 (“You’re on this list because you know there’s nothing better than the feeling of skiing in deep, untracked powder!”), and its distribution multiplied as followers like big-mountain skier Chris Davenport forwarded Gratz’s forecasts on to their networks of friends.

Gratz quit his insurance job in 2010 and, after raising capital and building a business plan, a year later launched OpenSnow.com. With a team of six contract meteorologists forecasting for major resorts in most regions (including Vail, Gratz’s turf), OpenSnow.com attracts an audience of 1.5 million, roughly 10 percent of the nation’s snowboarding and skiing population.

“Being here makes all the difference,” he says, ordering another round. “You can’t do what I’m doing sitting in a forecast building looking at a computer screen.”

Living the meteorologist’s dream: skiing the powder you predicted that very morning.