The competition, taking place on the biggest ramp of its kind in the world, served as a test for the Winter Olympics in the South Korean county in 2018.

Twenty-two-year-old McMorris, who won an Olympic slopestyle bronze medal at Sochi 2014, claimed his first World Cup victory in big air.

After landing a backside triple cork 1440 indy in his first run, McMorris was then the only competitor to nail a frontside triple cork 1440 mute.

That gave him a final score of 184.75 to improve on his third place finish at the last World Cup leg in Milan.

Another Canadian, Max Parrot, was second with a tally of 178.00 as Ryan Stassel of the United States claimed bronze on 177.25.

"I feel awesome," said McMorris. 

"It feels good to land that trick [frontside triple cork 1440]. 

"That was the trick I broke my femur on, and I haven't tried this trick ever since. 

"It's a big mental thing for me to overcome this. 

"And being first is the icing on the cake."

Canada's Sebastien Toutant, the leading qualifier yesterday, finished seventh overall with 152.50 points.

In the women's competition, Gasser backed up her victory in Milan by triumphing after topping qualification earlier in the day.

The 25-year-old, who won a World Championship slopestyle silver medal in Kreischberg last year, was a clear winner after pulling off a cab double cork 900 and a backside 720 mute.

She was able to enjoy a "victory lap" with the win already secure, nailing a frontside 360 nosebone to finish on 180.75.

Julia Marino of the US won silver on 157.00, someway adrift, as Britain's Katie Ormerod took bronze on 156.75.

"It's nice to win the Olympic rehearsal," said Gasser. 

"It's a great thing and it gives me a real boost of self-confidence aiming for Pyeongchang 2018."

The Big Air season will continue in Moenchengladbach in Germany on December 3.