Anne-Marie Knight shot a three-under 69 on Saturday and is alone in third place at minus-10.
Sorenstam was on fire early in her round with six birdies in her first eight holes. She made par at the ninth but admitted that 59 was on her mind on the front side.
'Oh, I definitely was thinking about another 59, but the wind got up around the turn and it was a little trickier,' said Sorenstam, who is the only player in LPGA Tour history to shoot the magical number when she did it in the second round of the 2001 Standard Register PING.
Sorenstam parred her first three holes on the second nine but tallied back-to- back birdies from the 13th to reach 13-under par for the championship. At the final hole, Sorenstam missed the green with a seven-iron and could not save par so her lead is only one over Stupples.
'I'm in a good position and tomorrow I'll have to play some good golf as there are lots of top players there,' said Sorenstam, a two-time winner of this event. 'There is still a bit of rust in the game, but I've got tomorrow to get it all cleared.'
Stupples mixed three birdies and a bogey in her round Saturday for a two-under 70.
'The wind was a little different out there, but to be in contention, I am very pleased,' said Stupples, who has not won as a professional. 'I am looking forward to playing with Annika tomorrow and I am going to have to try and be patient and play my own game.'
Grace Lee (69) and Jennifer Rosales (72) share fourth place at seven-under-par 209.
Nadina Taylor (66), Trish Johnson (69) and first-round leader Rachel Teske (71) are tied for sixth at minus-six.
Karrie Webb carded a two-under 70 and is tied for ninth with Scotland's Mhairi McKay, who posted a 71 on Saturday. The duo is knotted at five-under-par 211.