ROHNERT PARK, Calif. -- Stephanie Hamilton scored in the 109th minute, lifting Western Washington to a 2-1 victory against Cal Poly Pomona in the opening round of the West Regional of the NCAA tournament on Thursday at the Seawolf Soccer Field on the campus of host Sonoma State.

The No. 5-seed Vikings, now 18-3-0, advance to the regional semifinals Sunday against Sonoma State, the No. 1 seed in the West Regional.

Cal Poly Pomona, the No. 4 seed, completes its season 10-6-3. The loss snapped a school-record 11-match unbeaten streak for the Broncos.

Hamilton's goal came in the 109th minute as she finished with her left foot from the goal mouth after a long pass from Katherine Miccile was slightly deflected by a defender.

"We had a short corner, and it got knocked out to Miccile," Hamilton said. "I saw her look toward me, so I just tried to get there and get a foot on it."

The first half was tightly played, with each team getting just two shot attempts. CPP had the best opportunity of the period in the 20th minute, when off a scramble after a corner kick, a shot by Sarah Semenero was blocked on the goal line by WWU's Kristin Maris.

The Vikings also cleared a shot off the line in the 60th minute, as Miccile blocked a shot from eight yards by Angela Garcia.

"It was a great team win," WWU coach Travis Connell said. "Miccile cleared a ball off the line, we had a center back score a goal, and then Stephanie came up with a big one."

The Broncos opened the scoring in the 75th minute. Veronica Ramos got behind the defense down the right side and played a low cross to Samantha Stiles, who settled the ball and chipped it in from 10 yards.

WWU equalized less than two minutes later. A long free kick was won by a CPP defender, but her headed clearance was short, and center back Brianna Jones headed the ball just inside the left post from six yards.

"The first half was really tough," Hamilton said. "The second half of the game spread out more. We were able to connect a lot better in the midfield, which really helped."

CPP had a 15-14 advantage in shots. WWU goalkeeper Jamie Arthurs and Bronco netminder Sarah Rohlman each had six saves.

"Every team you face in the tournament is a good team. Pomona not only had good players, they played with a lot of heart," Connell said. "We had people missing, and other people stepped up. That's what winning in the tournament is all about."

Sonoma State is 16-2-2. The Vikings trail 8-4-0 in their series with the Seawolves, but have won the last three meetings.