Glamorgan 343 for 5 (Northeast 100, Ingram 69) beat Northamptonshire 340 for 5 (Vasconcelos 106, Keogh 100, Whiteman 88) by five wickets
Glamorgan took a big step towards the consolation prize of fourth place in Group B, chasing down 340 to beat Northamptonshire in a run feast at Sophia Gardens.
19-year-old wicketkeeper batsman Alex Horton, 44, and Billy Root, 39, saw their side home with an unbroken partnership of 81, after a century from Sam Northeast laid the platform, half centuries from Eddie Byrom and Colin Ingram also played a large part.
Centuries from Ricardo Vasconcelos and Rob Keogh, along with 88 from Sam Whiteman, meant Northamptonshire had been able to set an imposing total. Jack White was the pick of their bowlers, but the rest were expensive.
Glamorgan finished 343 for 5, chasing Northamptonshire's 340 for 5. Both sides came into the game knowing their were fighting for mid-table places, finishing fourth just below the play-off spots is the best they can do.
Northamptonshire chose first use of the batting track after winning the toss and openers Vasconcelos and Whiteman soon set about justifying the decision.
The half-century came up in eight overs, and the pair had put on 141 for the opening partnership when Whiteman fell to a super catch from Glamorgan captain Kiran Carlson at extra cover off the spin of Ben Kellaway for 88 from just 75 balls.
Vasconcelos was the bedrock on which they were able to build the innings. He was far from slow, scoring at just under a run a ball, but his presence gave a licence to Keogh to attack from the off.
Both batsmen would get centuries in a partnership of 117, Vasconcelos getting 106 before being bowled by Smith while Keogh smashed 100 exactly, off 75 balls, before being well caught on the boundary by Root from the bowling of Sam Gorvi
All the Glamorgan bowlers went for more than a run a ball in a performance which lacked bite. Gorvin finished with two wickets in his final over, while Jamie McIlroy was the pick of the bowlers until he too took some punishment at the end.
Glamorgan's openers Byrom and Northeast started watchfully until Northeast exploded into action with a six and three fours in four balls from Tom Taylor.
The Welsh County pair brought up their half century partnership after just seven overs, with the 100 coming up in the 12th over as Byrom took the initiative.
The pair reached their half centuries within a couple of balls of each other, Byrom getting there first. It took a diving, one-handed catch by keeper Lewis McManus to see the end of Byrom, trying to steer a short delivery from James Sales.
Colin Ingram arrived at the wicket in belligerent mood and after 20 overs Glamorgan has reached 157 for 1, which would be a respectable T20 score.
Ingram brought up his half century and the 200 for his team with the same shot in the 28th over, off just 43 balls. Northeast moved serenely onto three figures, taking just 104 balls, but next ball he was clean bowled by an inswinging full delivery from Jack White.
Ingram looked in control so it came as a surprise when he skied a leading edge to be caught and bowler by Tom Taylor for 69. Worse was to follow with Kiran Carlson caught on the boundary for 28, also off Taylor.
Ben Kellaway went cheaply to the leg spin of Alex Russell, but Root and Horton kept Glamorgan hopes alive. Horton made a real impact as he found the boundary regularly, while Root provided the calm head to get the job done.
