Half the field was unable to complete play because of a 4 1/2-hour weather delay.
The best round among those still on the Pinnacle Country Club course was being put together by amateur Stacey Lewis, who was 4-under on the front nine.
Prior to earning a spot on the LPGA Tour, McPherson appeared on a reality golf television program. She credited that experience with helping her on the circuit.
"It was warm up and take a couple of hours and it would be two or three hours before you hit one shot," McPherson said. "It really helped me out to really make every single shot count because that's all it is. If you can't hit the shot right then, then you're going home."