COEUR d'ALENE - The green flag dropped and the madness ensued.

Engines screamed, then roared. Snowmobiles surged forward. Racers crouched low over the handlebars, charging into corners, picking lines through slushy snow. They gunned their throttles and hit 35, 40 mph.

The race was on, even though the weather wasn't perfect on Saturday - the spring-like temperatures were too warm, there wasn't much snow, and huge mud puddles turned the Kootenai County Fairgrounds into a boggy quagmire.

But that's just winter in North Idaho.

"It's wet," said pro rider Michael Schramm of Missoula. "For the conditions that they had to work with, they did a pretty good job. Flat track, fast."

Visibility was poor, he added, because the sleds were flinging slush as they thundered down the track. Large ruts were another problem, and it was often hard to stay on course with such slippery snow underneath.

Nevertheless, Schramm muscled his Polaris around the half-mile course, working hard to stay at the front of the pack.

"It's definitely physical," he said of snowmobile racing. "It's a lot harder than people think."

The Coeur d'Alene event was an official Mountain West Racing competition, attracting amateur and professional racers from throughout the Northwest. Parker Toyota, Timbersled Products in Sandpoint and Coeur d'Alene Paving were three of the primary sponsors.

Cd'A Paving laid out the track and groomed the snow, creating a usable venue.

The action was fast and competitive, especially in the pro ranks. Sleds tangled up, and a few riders crashed. Ski-doo, Arctic Cat and Polaris machines, decked out with sponsorship stickers, flew around the narrow, twisting course.

"I love (the races), they're awesome," said Kristine Shaw of Coeur d'Alene, who watched from the sidelines with her 12-year-old son, Parker. "It's the adrenaline rush."

Some competitors rode snow bikes on Saturday - dirtbike frames with snowmobile appendages, a single ski in front and a churning tread in back. They bucked and swerved around the course, giving the racers quite a ride.

"It's squirrely. It's fun. The softer the snow gets, the better it gets," said Allen Mangum of Sandpoint. His company, Timbersled Products, manufactures the snow bike kits, which are growing more popular as the sport catches on.

The Coeur d'Alene event was his first snow bike competition.

"Haven't crashed yet, and it's pretty fun," Mangum said. "I think I'll just keep doing it. There's going to be three more races in the Northwest (this year). One's gonna be up at Schweitzer in April. I signed up for 'em all."

That Schweitzer Mountain event is the 2011 championship, scheduled for April 16-17.

Beth and Brent Seaton drove from Spokane to watch the races. They brought the kids along, too.

"Something to do on a winter day," Brent said. "It's kind of a mess out there (on the course). I guess that's the first time I've seen snow bikes. They look hard to ride. It looks like they'd be a lot harder to ride than dirtbikes."

Derick Driggs of Sandpoint was the only pro biker at the event. His bike promoted the Idaho National Guard, which set up an outreach tent near the grandstand. Driggs was the most accomplished snow bike racer at the fairgrounds - he'd won seven of the last eight contests, and was faring quite well on Saturday.

"It's so new of a sport, it's just like pioneering it, really," Driggs said. "It's a little bit different to control (than a dirtbike), different handling."

Kurt Olaveson stood at the starting line. He watched as the bikes and snowmobiles zoomed toward the first turn, full-bore, throttles wide open.

"Pretty cool," Olaveson said. "I'm from Moscow, I'm actually a student down there. I drove by and saw they had racing, and decided to stop. I've never actually seen (a snow bike) this close. They're pretty crazy."

He's a dirt biker himself, he said, but he's never ridden on snow.

"So I'd be interested to try one," he said.