The Tide's 7/166 when they had first use of the DXC Arena wicket in the T20 match looked vulnerable against a Storm bowling attack that had taken all before it in the month-long series.
James Bazley (42) and Antum Naqvi (24) combined for a 50-run partnership in the middle of the batting order that got the blue shirts to their score.
Mitchell Hope's sprawling catch at wide mid-off to catch a scorching Bazley drive from Josh Kann's bowling was the highlight of the innings.
The Tide were helped by 10 runs from rookie batter Xavier Tras (Extras), particularly the seven wides that proved the difference at the end of the game.
Jack Clayton's unbeaten 86 from 62 balls almost won the game for the Storm in their run chase.
Clayton came to the wicket at the fall of Josh Kann's wicket with only 21 on the board and was there at the death when wicketkeeper Michael Kudra was bowled by Wes Agar from the last ball of the match to leave them at 9-159.
Northern Tide skipper Jake Fraser-McGurk was happy to accept the early bragging rights for Sunday's 50-over final at the Marrara ground.
"It was a super win against the Storm who I think had only lost once, so to have them on Sunday in the final and beat them here is a bit of a pre-game bragging rights, but hopefully we can get the job done,'' McGurk told NT Cricket.
"We know we've got the team on paper, so if we turn up on the day we should go pretty well.''
The willow dominated leather in last Sunday's 50-over matches, where more than 1000 runs were scored at Marrara's DXC Arena and Palmerston's Cazaly's Arena.
A 92-run opening stand between Southern Storm pair Bailey Capel (96 from 77 balls) and Sam Fanning (26) set the scene for the purple shirts, who proceeded to make 7-292 in their turn at the batting crease.
Capel hit 12 fours and three sixes at the Palmerston ground against a City Cyclones attack that struggled on a flat pitch before finger spinner Andrew Richards bowled him four runs short of a deserved hundred.
Skipper Josh Kaan added to the mayhem with 72 from 55 balls, 32 of those runs coming in boundaries.
Cyclones skipper Dylan Brasher, who will play with the NT side in this month's Top End series against Academy sides from Big Bash sides Melbourne Renegades, Melbourne Stars, Papua New Guinea's national side and Cricket Australia Invitational X1, made a brilliant century in his side's run chase.
Brasher's 101 from 91 balls was marginally short of half the Cyclones' 223 in 44.5 overs.
Left-arm finger Hamish Martin's 4-36 _ including Brasher and fellow opener Jack Wood for a duck _ set up the Storm's 69-run win.
Northern Tide opener Blake MacDonald raced to a big hitting 115 from 97 balls in his side's huge 7-340 against the Desert Blaze at Marrara.
Canberra's MacDonald and Tasmanian Nivethan Radhakrishnan (69) set the batting tone with a 209-run opening partnership, MacDonald putting on a clinic with nine fours and six sixes in his innings.
Blaze skipper Dhuru Kant played a lone hand in his side's run chase, making a formidable 103 from 123 balls before a mistimed pull from left-arm spinner Radhakrishnan ended up in the hands of Same Kerber at mid wicket.
The Blaze ran into a fired up paceman Wes Agar, the South Australian shield cricketer, who snared 6-43 from his 10 overs, including the Blaze's top three batsmen for a total of four runs between them.
Sunday's final at Marrara's DXC Arena hits off at 10.30am. Admission for the 50-over match is free.