The Huskies will meet the North region champion on Friday at 9 p.m. in the Class 1A semifinals at University of Maryland-Baltimore County.
Northern (17-8) avenged a December loss to Williamsport, a 62-39 pasting in the Doub Classic. The tough inside defense all but eliminated Carrie Weimer and turned the Wildcats' outside shooting tentative.
Brooke Brenneman set the tone for the Huskies early, hitting three inside baskets in the first three minutes for six of her game-high 18 points and a 6-0 Northern lead. Williamsport never led.
"We were never able to shoot well enough and we never got off the mark from the beginning," Williamsport coach Curtis Graff said. "They wanted to play a half-court game and we wanted to go full-court, but we never scored to get that going."
Northern led 25-21 at the half and outscored the Wildcats 7-2 in the final seven minutes of the third quarter for a 32-25 lead.
Williamsport (14-10) started to take the momentum with its press in the fourth quarter, pulling within 36-33 on a Britt Jones foul shot with 3:33 remaining. But on their next possession, the Wildcats turned the ball over and Brenneman fired the knockout blow with an eight-foot jumper to regain a five-point lead with 2:56 left.
"We never got over the hump," Graff said. "We got it to within three or four, but we couldn't get that big basket or big stop. When you can't do that, it allows the team ahead to relax. Northern did everything it needed to win."
Erin Gross and Jones led Williamsport with seven points. The Wildcats' loss leaves Washington County without any boys' or girls' representative at the state tournament.