Northern Diamonds 248 for 8 (MacDonald 92) beat North West Thunder 175 for 8 (Levick 3-22) by 73 runs
Alex MacDonald's superb 92 set up a resounding Northern Diamonds victory - by 73 runs - over North West Thunder at Liverpool and moved them to within one win of the Rachael Heyhoe Flint Trophy final.
The 28-year-old left-hander posted her highest domestic score in six years to underpin a commanding 248 for 8 from 50 overs, hitting 10 fours and two leg-side sixes in 110 balls.
The Diamonds then comfortably defended their total on a slow and low pitch to secure their fourth successive victory and move to 18 points at the top of the North Group as the Thunder were restricted to 175 for 8 from their 50 overs.
Experienced leg-spinner Katie Levick starred with 3 for 22 from 10 overs, while MacDonald also struck once with her medium pacers.
A win over second-placed Central Sparks at Emerald Headingley on Sunday will seal their progression to the September 27 final at Edgbaston.
Having been invited to bat, the Diamonds had to recover from 57 for 4 in the 17th over, with new-ball seamer Alice Dyson claiming two wickets. Netherlands international Sterre Kalis was bowled by an unplayable grubber from Dyson for a third successive duck.
But MacDonald, a Yorkshire women's player who scored a century for Gloucestershire in 2014, expertly led the recovery with help from Jenny Gunn's 29, and Bess Heath and Phoebe Graham, who reached 23 and 29 respectively.
MacDonald, batting at No. 5 and particularly strong on the sweep, was handed a reprieve on nought when, pulling, she offered a tough chance to a diving Laura Marshall at square-leg. And the hosts were made to pay.
Seamer Laura Jackson was the pick of the Thunder bowlers with 2 for 23 from nine overs, while skipper Alex Hartley also struck twice.
In reply, the Thunder lost wickets all too regularly to make any significant impact as their chances of final qualification were ended with a third straight defeat following an opening round win.
After Beth Langston claimed the early wicket of Georgie Boyce, Levick had Marshall caught at short cover, Ellie Threlkeld lbw and Nat Brown caught behind as the score fell to 69 for 4 in the 21st over.
Fifth-wicket pair Laura Jackson and Danielle Collins shared 28 inside 12 overs as the inexperienced Thunder side held their cross-Pennine rivals up. MacDonald continued her memorable day, bowling Collins for 18 to all but end the contest at 97 for 5 in the 32nd over.
Sixteen-year-old Liberty Heap added 15 and Dyson top-scored with a late unbeaten 25, while Diamonds captain Hollie Armitage and Langston finished with two wickets apiece in a bonus point win.