Blasberg holed a key birdie putt at the par-4 17th and a closing par gave the four-year tour veteran a chance to become the 30th winner in the tournament's 30-year run.
"I was a little worried (Thursday) morning when it was about 38 degrees with wind and rain," Blasberg said. "But it was so nice having the practice rounds in the same conditions because I practiced with a lot more rain gear on than I had on today."
The University of Arizona product has an overnight lead over Na On Min and Karine Icher, who share second place at 5-under 67.
Defending champion Young Kim shot 2-over 74 and is tied for 82nd place.