After the slopestyle riders took their bow on Wednesday, it was then the turn of the stunt ditch specialists. The Burton US Open halfpipe is never short of drama, so all eyes were on Vail as the semi-finals got underway.

Conspicuous by his absence was newly minted Olympic champion Shaun White, who is probably already practicing his skateboard run for Toyko 2020. Chloe Kim was in town though, looking to cement her dominance over the women's event.

"Despite managing to squeeze in two more hits than Chloe, Maddie scored less than a point higher"

  1. Maddie Mastro - 85.87
  2. Chloe Kim - 85.12
  3. Xuetong Cai - 83.12
  4. Haruna Matsumoto - 79.99
  5. Jiayu Liu - 76.75
  6. Kelly Clark - 76.37

We've talked often about how Chloe is so good these days that even her safety run is often enough for gold. Indeed, in Pyeongchang she was already comfortably leading the field before stepping things up further still in her victory lap.

She was definitely coasting in this qualifying event, with back-to-back 720s making up two of the five hits in her highest-scoring run. Comfortably through to the final, then, but not in the top position.

That honour went to Maddie Mastro, who put down a frontside 900 right out of the gate and followed it up with a backside air, front 7, Haakonflip, crippler, backside 5 and front 5 (with a whiff of Shaun's 'Skyhook' about it) to take the top spot.

Despite managing to squeeze in two more hits than Chloe, Maddie scored less than a point higher. If she's to fend off the Olympic champ at full steam, she'll need to find something more in the final.

Chinese rider Xuetong Cai took the third-highest score; her run - featuring an alley-oop air to fakie that we don't see enough of these days - put her ahead of fellow finalists Haruna Matsumoto, Jiayu Liu and Kelly Clark.

The Americans, Chinese and Japanese riders continue to dominate the women's event, with only three of the seventeen finalists not coming from one of those countries. There's no Swiss riders in the top tier at all, which is particularly strange given the quality of the Laax halfpipe, which has propelled the likes of Iouri Podlatchikov, David Habluetzel and Pat Burgener to the upper echelons of the men's event.

  1. Ayumu Hirano - 92.37
  2. Chase Josey - 89.12
  3. Scotty James - 87.25
  4. Raibu Katayama - 84.75
  5. Pat Burgener - 80.75
  6. Ben Ferguson - 80.50
  7. Jake Pates - 75.25
  8. Jan Scherrer - 71.62
  9. Derek Livingston - 67.12
  10. Naito Ando - 65.00

Of those three, only Pat made it to Vail, with the other two still recovering from nasty injuries. With the absence of both iPod and Shaun, the men's event would most likely be a straight bout between the silver and bronze medallists from Pyeongchang - Scotty James and Ayumu Hirano.

Sure enough, the Australian was leading the field after the first run, with Chase Josey not far behind. Ayumu had more to do, but as he would be the last man to drop, everyone else had to be ready for him to leapfrog the field.

"Ayumu did what he needed to do on the final run of the day"

Chase certainly did his best, stepping up from 2nd to 1st with an improved run that featured his trademark mirror-image approach to pipe riding.

However, Ayumu did what he needed to do on the final run of the day. With his two brothers Eiju and Kaishu looking on (both of whom failed to make the cut) he kicked things off with a big backside air followed by a frontside double cork 1080, switch front double 10, front 900 tail, back 9 mute, and a frontside double 1260 to finish.

Sadly Rene Rinnekangas didn't progress to Saturday's final, but anyone who can enter both halfpipe and slopestyle is a winner in our book - and on the day he delivered the most entertaining snowboarding of the whole contest. As well as letting Nik Baden and Gimbal God poach with him on both runs, he focused on hand-dragging, lip-bashing, backflipping good times.

Joining Scotty, Ayumu and Chase in the final are Raibu Katayama, Pat Burgener, Ben Ferguson, Jake Pates, Jan Scherrer, Derek Livingston and Naito Ando.

If last year's final is anything to go by, then Saturday will be one not to miss. Stay tuned.