Utah (36-15), which was swept in a three-game series at home by Washington two weeks ago, fell behind 5-0 after two innings, but pulled within 5-3 on a three-run homer by Kelly Martinez in the fourth.
Flores, a sophomore catcher, answered with a grand slam off reliever Hailey Hilburn in the bottom half, her 12th homer of the season, as the Huskies pushed the lead back to 9-3.
Taylor Van Zee added a solo homer for Washington in the sixth. Utah loaded the bases with one out in seventh, but managed only one run on Alyssa Barrera's fielder's choice grounder.
Sophomore right-hander Taran Alvelo (31-6), who recorded all three victories in the sweep at Utah, as well as all three regional victories for the Huskies, allowed four runs on nine hits, striking out one and walking one.
The Huskies (47-11) took a 4-0 lead in the first, jumping on junior starter Miranda Viramontes (14-4), who failed to retire any of the five hitters she faced.
Ali Aguilar walked to open and Sis Bates reached on a bunt single that barely eluded Viramontes. Casey Stangel followed with an RBI single to right.
Flores, the Pac-12 RBI leader, then lined a 1-1 pitch over the left-field fence for a three-run homer.
Van Zee singled, chasing Viramontes. Hilburn relieved and enticed Julia DePonte into a 5-4-3 double play.
Trysten Melhart beat out a swinging bunt for the Huskies' fifth hit of the inning, but was thrown out trying to steal second on a perfect throw by catcher Martinez. It was the first time Melhart was caught this season after 19 consecutive successful steals.
Washington added a run in the second on a two-out walk to Aguilar and consecutive singles by Bates and Stangel. Flores walked to load the bases, but Hilburn escaped by retiring Van Zee on a liner to left.
R Sophomore catcher Morganne Flores hits a grand slam and three-run homer to pace Washington.
• Sophomore right-hander Miranda Viramontes failed to retire any of the five batters she faced, giving up four runs on four hits with a walk in the first inning.