Second-round leader Yani Tseng is a stroke back, while 2011 champion Lexi Thompson was a further shot adrift, alongside Kim Sei-young, Tiffany Joh, Sydnee Michaels and Julieta Granada.
Americans Sadena Parks and Cydney Clanton share eighth place on seven-under with Brittany Lang part of a five-player group lurking just four shots off the lead.
A majority of the field needed to complete the second round on Saturday morning after a weather delay the previous afternoon and the third round is set to resume early on Sunday with all 75 players that made the cut still on the golf course.
Tournament organisers will be hoping the weather stays clear and the event can be completed on a marathon day with the leading trio set to play a total of 31 holes around the par-72 course at Capitol Hill near Montgomery.
"It's going to be a marathon," Ernst told reporters. "There's a lot of golf left. It will basically just be get as many birdies as I can. I know the scores are still going to be low. It's just going to be more continuous golf than usual.
"We'll finish that third round up and then probably get a little lunch and go right back out there. It will be good, kind of be able to get into a little bit of a groove early hopefully and then just kind of carry that on throughout the day."
(Writing by Jahmal Corner in Los Angeles; Editing by John O'Brien)
