Upshur hit 5-of-9 3-pointers and Jacobsen finished 8 of 11 from the field as Northern Arizona (13-16, 10-8 Big Sky) shot 50 percent from behind the arc.
A layup by Upshur with 1:43 remaining gave NAU a 65-54 lead but Weber State (16-10, 13-5) used a 12-2 run, sparked by a 3-pointer and capped by a layup from Davion Berry, to pull within one with 38 seconds to go.
Upshur made 1 of 2 free throws before Berry was fouled on a layup with 9 seconds left in regulation. He missed the free throw, sending the game into overtime.
Upshur's 3-pointer with 11 seconds left in the extra frame proved to be the game winner.
Berry led the Wildcats with 23 points.