Powder Hound Passions Ski Meteorology Go-to Site Mountain Forecast


When Joel Gratz publishes weather on the OpenSnow site, skiers and snowboarders can be sure that he has done everything to make it as reliable as possible. That’s because Gratz, a Boulder resident who skis 60 to 75 days a year, also relies on those predictions.

Gratz is a powder hunter and weather geek who started out using his meteorology degree to decide where and when to ski. Fifteen years later, OpenSnow is the go-to mountain weather site for Colorado winter sports enthusiasts — and even ski resort managers.

“I’m an only child, which means I’m a little selfish,” Gratz said. “I don’t know if I would be able to work this hard on something if I didn’t have skin in the game, if I didn’t do it for selfish reasons. I’m glad there are other people who like it, but most of all it was me and my friends trying to have an amazing time chasing fleeting conditions, perishable conditions.

During the ski season, Gratz publishes “Daily Snow” reports with forecasts, weather conditions and notable snow accumulations. A “Favorites” feature allows users to get recent snow totals and 10-day forecasts for specific resorts and certain backcountry areas. There are also links to webcams covering highways, resort mountain cameras and snow measuring stakes.

He assembled a team of fellow meteorologists to provide forecasts and snow reports for other parts of the country. Soon OpenSnow will add reports for European stations.

Although he declined to give specific figures on the traffic generated by his site and phone app, he said they reach three million users a year. OpenSnow offers several free features as well as a subscription option with additional information that costs $29.99 per year.

“I’m a huge fan,” said Arapahoe Basin COO Alan Dorsroth. “I use it several times a day. It gives very good forecasts and constantly updates them. I use it to find out what can happen to the Arapahoe Basin, but I also keep an eye on the rest of the country with him.

New for this ski season, paid subscribers can tap anywhere on a map to get detailed forecasts, recent snow totals and current conditions for that location. Called Forecast Anywhere, this feature is sure to be a boon for cross-country skiers, snowshoers, and summer hikers.

Gratz, 41, says he became “addicted to the climate” at the age of 4 when his parents took him skiing for the first time. He grew up in Philadelphia and became an avid skier despite the limited terrain and harsh East Coast skiing conditions, which often included rain, freezing rain and sleet.

His home mountain was Shawnee Mountain, a small area in the Poconos with a vertical drop of 700 feet. Occasionally the family would visit Mount Snow in Vermont, a 300 mile trip. He once skied at Smuggler’s Notch, another ski area in Vermont, when the wind chill temperature was minus-60.

Gratz earned her meteorology degree at Penn State and moved to Colorado in 2003 for graduate school.

Open Snow founder Joel Gratz works from his home in Boulder on Wednesday, Oct. 12, 2022. (Photo by AAron Ontiveroz/The Denver Post)

“I didn’t realize powder was a thing until I skied west,” Gratz said. “Then a friend’s uncle introduced me to powder, which I skied horribly the first time, because an East Coast skier doesn’t know how to do it the first time. I became quite captivated, because it was super fun and it was a big game where to find the best powder? »

He began using his training in meteorology to plan ski trips. Soon, friends were texting her asking the same questions. He wrote his first forecast by email in December 2007 and launched OpenSnow on November 1, 2011. It has been a full-time activity for him since 2010.

Like television meteorologists, Gratz relies on extremely complicated computer models disseminated by government websites around the world to make his forecasts. Data for these models comes from satellites, ground weather stations, aircraft, weather balloons and radar.

“These models are mathematical equations,” Gratz said. “It’s a computer program. It’s no different than Microsoft Word or a browser or an app on your phone. It’s just really, really, really, really complicated. It takes into account what the weather is doing right now, runs it through a bunch of equations and tries to figure out what the weather will do in the future.

Most of these models have been developed by national governments – the oft-cited European model, for example – because they are very expensive to create and operate.

“You need big supercomputers to run them,” Gratz said. “The models are really complex and it takes hundreds – sometimes thousands – of people to create them. It’s an incredible feat of engineering to collect all this data from around the world, in near real time, put it into a model two to four or more times a day, and do it reliably. All of that goes into the model, the model runs its math equations, and a few minutes or hours later you get a bunch of data.

Because models often disagree, Gratz typically develops his forecasts after studying five to 10 of them. His long experience tracking mountain weather also comes into play.

“If I had a favorite model, I would take a lot less time to forecast because I would only be looking at that one,” Gratz said. “You have to look at all the models and mix them in your mind around ‘What weather patterns have I seen before? Does that make sense to you? I know there are biases in the models. Then you write it down.

Forecasts are never perfect because there are too many variables.

An example is the path of Hurricane Ian last month. For a week, it was clear that a major hurricane was headed for Florida’s west coast, but the closer it got, the harder it was to predict where exactly it would make landfall. Two days before coming ashore near Fort Myers, it was expected to hit the Tampa Bay area, more than 100 miles to the north.

“Just like you saw Ian wobble a bit, the same can happen here for the snow forecast,” Gratz said. “You can tell a storm is coming a week in advance, but where is that heavy swath of snow going that makes or breaks your powder day? Sometimes it’s really hard to tell.

Gratz has no statistics on the accuracy of its predictions.

“My anecdotal answer is that the forecast is about right about a third of the time, in-stadium about a third of the time, and wrong about a third of the time,” Gratz said.

Gratz is not a fan of long-term forecasts because they are too unreliable.

Open Snow founder Joel Gratz at his home in Boulder on Wednesday, Oct. 12, 2022. (Photo by AAron Ontiveroz/The Denver Post)
Open Snow founder Joel Gratz at his home in Boulder on Wednesday, Oct. 12, 2022. (Photo by AAron Ontiveroz/The Denver Post)

“A week out is a good time where we have decent confidence about what’s going to happen,” Gratz said. “Sometimes after 10 days you can get an idea, maybe it’ll be stormy, or maybe it’ll be hot and dry, but the 10-day details aren’t very good.”

And, as was the case with the hurricane, forecasts are updated and refined as snowstorms approach.

“You always consider new information,” Gratz said. “If you look at Google Maps for traffic, you look again and it changes, you’d probably go in a different direction. The same thing happens with weather. And a lot of times I’m still sweating bullets the night before , ‘Will this prediction work?’

For forecasts outside of the ski season, there is an OpenSummit spin-off site with useful weather information for hikers and campers. An OpenSnow subscription covers both.

“I couldn’t be happier with how it ended,” Gratz said. “There were 10 to 15 years of absolute sleepless nights, hard work, setbacks. When I wrote my first forecast, if someone said, ‘In 15 years, where do you want to be?’ we are right there.

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