After rumbling up for nine phases off the ruck, Ruapehu got another penalty and Scarrow steadied himself to make it 8-0 just before halftime.
But Hunterville were confident they could run that down with the wind behind them, and although Parkes was well away with his first penalty attempt, he would redeem himself 10 minutes later with a very clever fake-out try.
Awarded a penalty right in front, Hunterville first-five George Gisesen went to the mark and while glancing at the posts, delayed and delayed as Ruapehu set for the kick, then just tapped it for a charging Parkes who dived fully extended to score, 8-7.
But despite running into the wind, Ruapehu came storming back, as second-five Kerry-Jon Wikitera gutsed out a knee injury to make consecutive surging runs to put his team hot on attack.
However, now kicking into the breeze, Scarrow had better accuracy but could not reach the distance.
Then the defining moment came in the 65th minute, as Ruapehu fouled during a Hunterville clearance and referee Gordon Ririnui awarded the penalty where the ball landed.
With halfback Nick Tipling holding the ball steady, Parkes calmly slotted the 35m attempt to give his team the lead.
Hunterville tried to put the game into deep freeze and it appeared Ruapehu's last chance had gone when a frustrated Wikitera threw a punch in front of the touch judge and was sent off with less than five minutes left.
But Ruapehu drove the ball all the way back from their 30m zone and got the penalty, only for Scarrow's attempt to just fall desperately short in front of the posts.
Incredibly, Hunterville missed touch and Ruapehu ran it back to get another kickable chance on the very last play.
But from 35m out the wind again said "no" and Scarrow's identical attempt fell short into Parkes' waiting arms, with the ball kicked dead for fulltime.
"Finals footy eh," shrugged Ruapehu coach James Rowe.
He was still very proud of his side's development after they were humbled in last year's final 38-3, as despite Hunterville's sixth straight title it had been a much more competitive grade overall this season.
"We've got these schoolboys, five under 19, and they've all grown this year.
"[Hunterville's] just got a lot of old heads in good positions."
Relieved Hunterville coach James Kilmister said given the conditions, their best hope had been to hang onto the ball wherever on the park to "starve" Ruapehu for as long a period as possible in the first 40 minutes.
"The wind was a factor, really. 8-0 at halftime, we thought that would be alright.
"We haven't got a big forward pack but we contested well there, which we have all year."
Senior championship - Power Farming (PN) Hunterville 10 (Scott Parkes try, pen, con) bt Ruapehu 8 (Cody Scarrow try, pen). HT: 8-0 Ruapehu.