Released to play in the Twenty20 clash to re-find some form, Munro was at his belligerent best, taking two wickets and then bringing up a rapid 50 from 28 balls.
However, two balls later, he crushed a rasping drive straight to Dean Brownlie, who clung onto the scorching shot to remove Munro for 54.
Earlier, Corey Anderson (36 from 22 balls) and recent international call-up Daryl Mitchell (37 from 28) contributed in Northern Districts' 196-8, before fellow Black Caps Scott Kuggeleijn (1-35) and Ish Sodhi (1-39) took wickets in Auckland's chase.
However, Munro's blistering start set up Craig Cachopa (60 from 39) and Robbie O'Donnell (45 not out from 26) to see Auckland home with four balls to spare, and book their spot in the finals.
Munro will fly down to Wellington tomorrow morning to re-join the Black Caps ODI squad, with New Zealand set to unleash their third different opening partnership in the last three games.