Put into bat, Vipers raised a competitive 261-7 from 50 overs thanks to half centuries from Georgia Adams, Danni Wyatt and Charlotte Dean. Heather Knight and Sophie Luff threatened to make light work of that when scoring 67 and 60 respectively in a hundred partnership for the second wicket, only for Storm's chase to hit the rocks in the face of an inspired spell from Norris, who was ably supported by fellow seamers Lauren Bell, Maia Bouchier and Paige Scholfield. Handily-placed on 149-1 in the 26th over, the hosts suffered a dramatic collapse, losing seven wickets for 31 runs in 11 overs and, despite the best efforts of tailenders Claire Nicholas and Lauren Parfitt, were bowled out for 239 inside 48 overs.
Victorious in their opening two fixtures, Vipers are top of the group and, with four matches to play, have put themselves in with a decent chance of making the final at Edgbaston on September 27.
Norris, who plays for Horsham Cricket Club, said: "That was a really emotional win for us. When Heather Knight was going well, it didn';t look as though 261 was going to be enough. She's a world class player and someone who can win a match from any position. When I got her out, I knew it could be a turning point. I was pleased and surprised by the way I bowled, but I had great support from the others. Storm are a top team and that's a really big win for us. We're playing well and feel we can go all the way."
Storm appeared to be cruising to victory when Knight and Luff staged an increasingly authoritative partnership of 130 in 22 overs, the second wicket pair both registering half centuries to put their rivals firmly on the back foot. When Knight was caught behind off a Bouchier no ball on 23 and then dropped by Scholfield at mid-wicket off the same bowler on 52, it looked like being Storm's day.
But Scholfield atoned by catching Luff at mid-on off the bowling of Adams, an interjection that proved a defining moment in the game, sparking an unexpected collapse in which the hosts slipped from 149-1 to 180-8. Left-arm seamer Norris was at the heart of the turnaround in fortunes, claiming four wickets in a devastating 19-ball burst, including the prized scalp of Knight, who was bowled for 67 via a bottom edge, at which point Storm were required to score a further 102 from 20 overs with their batting inspiration back in the changing room. Having already had Georgia Hennessy caught at the wicket, Norris again struck twice in quick succession to remove Katie George and Alex Griffiths, both held by the ubiquitous Scholfield.
Bell then bowled Nat Wraith to finish with 2-41 from nine overs and Scholfield accounted for Emma Corney, after which Nicholas and Parfitt did their best to make a game of it, staging a spirited stand of 47 in eight overs for the ninth wicket. But Adams, who finished with 3-23, claimed the wickets of Nicholas and Niamh Holland, leaving Parfitt unbeaten on 33.
Having posted a match-winning opening stand of 111 in Saturday's seven-wicket triumph over Sunriders, Adams and Wyatt picked up where they left off to provide Vipers with the perfect start, staging an assured alliance of 105 in 19.4 overs on a surface that held few demons for batsmen. Taking advantage of the fielding restrictions and some wayward bowling, these two proved adept at rotating the strike, running hard between the wickets and scoring primarily behind square to plunder 90 runs from the first 15 overs.
England one-day star Wyatt established herself as the senior partner, taking few risks in cutting and pulling her way to a 54-ball half century which included half a dozen boundaries. Demonstrating sound shot selection, Adams realised the same landmark from 70 balls as runs came easily against a Storm attack that lacked express pace and penetration.
Quickly realising that it was difficult to hit down the ground and that taking the pace off the ball would generate additional bounce, Luff called upon her triumvirate of off spinners in an attempt to change the dynamic, a strategy that paid dividends when Wyatt uncharacteristically gave Fi Morris the charge and saw her middle stump knocked back. Attempting to make the most of the platform afforded by the openers, Bouchier went aerial. only to play one shot too many, loft a flighted delivery from Knight straight to mid-off and depart for 16 in the 27th over. When Adams was called through for an ill-advised single by Dean off the bowling of Knight and comprehensively run out for 55 by Luff's smart pick-up-and-throw from backward point, Vipers had lost two wickets in 10 balls and, at 149-3, were in danger of losing crucial mid-innings momentum. Scholfield succumbed to Nicholas for nine, top-edging a sweep to Parfitt at short fine leg, and Emily Windsor was caught behind for 14 off an arm ball from Knight, who extracted extra bounce to finish with 2-36 from 10 overs to help Storm wrest back a degree of control.
Ella McCaughan attempted to open up the off side and was bowled by a ball that nipped back at her from George, while Carla Rudd was lured onto the front foot by Hennessy and fell prey to a smart stumping from the exemplary Wraith as Storm's death bowlers continued to turn the screw. Determined to make amends for running out her captain, Dean remained unperturbed by the fall of wickets at the other end, putting fielders under pressure with clever placement and hard running in a stabilising innings of 60 not out from 70 balls, with four boundaries, to haul the visitors to respectability.
Western Storm skipper Sophie Luff said: "Losing those wickets in the middle phase of the innings proved the difference. I've not had much chance to bat with Heather this year, but we were going really well and had got ourselves ahead of the rate. It all changed when I got out and, perhaps the situation got the better of one or two of the younger girls thereafter.
"I thought we did really well to pull the game back after they made such a good start and, with Danni Wyatt and Georgia Adams at the crease, I think I would have settled for chasing 250 or 260.
"Our spinners brought us back into it, but we couldn't follow it up with the bat. We now lose Katie (George), Heather (Knight) and Anya (Shrubsole) to England, so there will be an opportunity for some of our other young players to make their mark in the remaining games."