Kris Yanku added 15 points and seven rebounds for the Lumberjacks (7-9, 2-1 Big Sky), sinking 10 of 12 free throws. Quinton Upshur struggled from the field, hitting just 1 of 10, but went 9 of 10 from the line for 11 points.
Casey Oliverson paced Southern Utah (3-11, 0-3) with 12 points and seven rebounds, while Race Parsons and Travon Langston each contributed 11 points. The Thunderbirds gave up 19 points off turnovers and another 17 on second-chance opportunities.
Northern Arizona held a comfortable lead, 56-38 with 6:37 remaining, but had to sweat out the final minutes.
The Thunderbirds reeled off a 24-9 run, pulling within three after James McGee's 3-pointer with 17 seconds left. The Lumberjacks made 5 of 6 free throws to hang on.