Western Storm 180 (Wellington 45*) beat Sunrisers 150 (Macleod 48, Griffith 39, Skelton 5-29) by 30 runs
Chloe Skelton's five-wicket haul propelled Western Storm to victory at Radlett and dealt a severe blow to Sunrisers' hopes of reaching the Rachael Heyhoe Flint Trophy semi-finals.
Off-spinner Skelton finished with 5 for 29 as the home side were rolled over for 150, having earlier played a valuable role with the bat in support of Amanda-Jade Wellington's counter-attacking 45 not out that lifted Storm to a competitive total of 180.
Sunrisers looked on course to chase that down through Cordelia Griffith (39) and Alice Macleod, with a season's best of 48, only for Skelton to turn the contest back in the visitors' favour.
Storm's success was only their fourth of this year's competition and left Sunrisers needing to win their final fixture away to Southern Vipers to maintain their chances of advancing to the knockout stage.
Having won the toss, Sunrisers inserted the visitors and immediately seized control of the game, although it took them until the ninth over to make inroads when Kate Coppack took a tumbling return catch off Sophia Smale's leading edge.
Emma Corney and skipper Sophie Luff made steady progress, guiding their side to 61 for 1 before the introduction of Sophie Munro, who yorked Corney for 29 in her first over and finished with 3 for 42, triggered a clatter of wickets.
Luff was bowled leaving a slower delivery from Eva Gray that seamed back to hit her off stump and a miserly second spell from leg-spinner Jodi Grewcock yielded two wickets as Storm slumped to 115 for 8.
However, their prospects were salvaged by the tail, with Skelton and then Ellie Anderson providing staunch support for Wellington's spirited counter-attack to extend the innings by a valuable 65 runs.
The Australian steered Munro to the point boundary to bring up Storm's 150 and drilled her next ball over the top for six as she and Anderson frustrated the home side in a partnership of 41, the highest of the innings.
Abtaha Maqsood eventually finished off proceedings in the 47th over, bowling Anderson with a flighted delivery to leave Wellington five short of her half-century - but having done enough to lift Storm morale.
That received another boost at the start of Sunrisers' reply when Anderson dismissed both openers cheaply, with Jo Gardner picking out the midwicket fielder before Grace Scrivens played around one and was bowled.
When Skelton had Grewcock caught behind off her fourth delivery, the home side were wobbling at 44 for 3, but Griffith adopted a pugnacious approach, pummelling Anderson for successive off-side boundaries.
In tandem with MacLeod, Griffith got Sunrisers back on track with a partnership of 46 from 58 balls and looked comfortably set on 39 when she swung Skelton into the hands of deep midwicket.
But MacLeod took up the baton, hitting confidently over the infield and took the total past 100 by dispatching Wellington to the rope as well as taking successive leg-side boundaries off Smale.
A half-century seemed to be MacLeod's for the taking until she was thwarted by a stunning one-handed catch from Alex Griffiths at short cover - and that proved to be a turning point.
Storm's spinners pressed home their advantage, with Skelton capturing three of the last four wickets to complete the win with 10.3 overs to spare.
