The Sky Sports Living for Sport Athlete Mentor clocked the time on Thursday after his attempt was unexpectedly brought forward due to anticipated bad weather this weekend.
Barrow, 20, admitted the challenge had been "a step into the unknown" but was ecstatic after eclipsing the unofficial British record of 82mph set by his own coach, James Foster.
"This record has been two years in the making," said Barrow, "and it feels incredible to have the title to my name.
"The forecast for the weekend meant I only had one day of riding before the challenge - and even then I wasn't able to get to the track.
"Mentally, I had to turn my head around very quickly and think 'I know I can do this' so why wait? I knew I was well prepared and, in truth, I was raring to go."
Barrow recorded a speed of 88.6mph on his first run even though he was uncertain how his boots and board would stand up to the test.
"It was a step into the unknown," he reflected. "Most of the time when people try speed records on a snowboard they use a board that is really long and thin and they wear ski boots.
"I don't believe that is snowboarding - so I used a regular snowboard and normal boots to make it authentic, but I didn't know how they would react. The board was quite unstable on the first run in comparison to what I'm used to but I got the hang of it!"
Barrow was told he'd have to start 20m higher up Mont Ford if he wanted another attempt, increasing the run length to around 880m with a vertical descent in the region of 430m.
"It was a huge step up," he said. "The first start position was scary enough, but I then had to sit up at the second for about 45 minutes waiting which gave me time to wondering whether or not I should do it!
"Everyone was telling me that I was crazy to even think about going off that start but I knew I had to go down at some point, so I thought 'why not here?' After a lot of sitting around I did it and I'm so happy I did.
"I knew I was faster the second time because the board kept on accelerating, accelerating. It was an incredible feeling and I felt a lot more comfortable. I was over the moon when I saw the time."
Barrow - part of the British Snowboardcross Team - hopes that his achievement will resonate with students participating in the Sky Sports Living for Sport scheme and encourage them to reach their full potential.
As an Athlete Mentor on the initiative, run in conjunction with the Youth Sport Trust, Barrow is a keen advocate of the scheme's 'Six Keys to Success' - which include mental toughness, hunger to achieve and breaking barriers - and insists they continue to help him to fulfil his goals.
"Everything I've ever done in this sport uses the Six Keys - especially when it comes to breaking barriers.
"So many people told me not to even attempt this challenge that I did have my doubts but no matter how scared I was I decided to do it.
"My hunger to achieve helped me go down the slope in the first place because I definitely wouldn't do it if I didn't want it so badly.
"It drives me on and I still want to break that 100mph barrier. No-one thought I could hit 150kmh (93.2mph) with the boots and the board that I had because they'd never seen anyone do that before.
"But that just goes to show how important it is to follow your dreams."
Since Sky Sports Living for Sport launched in 2003, around 74,000 young people in over a third of schools across the UK have benefitted by using sport to improve their lives - including the winner of this year's Sky Sports Living for Sport Awards, Wayne Instrell. Watch his story here...