Minjee Lee, two strokes behind playing partner and overnight leader Hall entering the final round, had a disastrous 77 to blow any chance of claiming a second LPGA victory this season.

The 22-year-old could not find a birdie on Sunday in her five-over round and finished fourth at 11 under.

"It was very bad," Lee said. "I didn't really have my 'A' game on."

Her compatriot Su Oh carded a three-under 69 to move up to a share of ninth at seven under – in a group which included American World No.5 Lexi Thompson (70) in her third event after a three-week break for emotional and mental fatigue.

Alex birdied the final five holes in a front-nine 30 to take the lead and added birdies on the par-5 12th and par-4 15th at the tree-lined Columbia Edgewater Country Club.

She made her only bogey of the day on the par-4 18th, leaving her at 19-under 269.

RIGHT: Minjee Lee has now posted back-to-back top-five finishes. But she will be disappointed after shooting five-over 77 in the final round of the Portland Classic. PHOTO: Jonathan Ferrey/Getty Images.

"My goal was eight under to give myself a chance but I even thought maybe that wouldn't have been good enough," Alex said.

"It was just an incredible day. I'm proud."

Alex matched the course record with a 62 on Thursday, then shot 71-71 to begin the final round six strokes behind Women's British Open champion Hall.

"It was tough to back up the first round with some good rounds," Alex said.

Hall had a closing round of 75.

"The pin positions were really, really tough," she said. "The front nine was unbelievable. I couldn't even get to hardly any of them.

"I was just trying to stay patient and do what I could to kind of stay in it. I mean, she shot, what, seven under? That's incredible. ... My hats off to her."

Japan's Ayako Uehara was third at 13 under after a 69.