She finished off a 68 with a final-hole par to cap the rain-delayed third round on Sunday morning and take a share of the lead with Mi Hyun Kim heading into the last round.
Gulbis and Kim had three hours to wait before teeing off for the final 18 holes.
Gulbis had rounds of 67, 66 and 68 and is at 12-under 201 along with Kim, a South Korean star who has won six times in her 7 1/2 years on tour. Kim finished off a third-round 67 after earlier rounds of 68 and 66.
The leaders were all on the back nine of the third round on Saturday when play was suspended at 8 p.m. so course workers would have an hour of daylight to rebuild traps and squeegee water. A series of thunderstorms wreaked havoc on the second and third rounds.
Gulbis, who often models for magazines and calendars, is one of the tour's best-known players. Large galleries follow her every move. Still, she is winless in her first 125 tour events.
A shot back at 11-under 202 are Paula Creamer, Reilley Rankin and four-time Farr winner Se Ri Pak. Pak, trying to match Mickey Wright's LPGA Tour record of five victories in one event, had a 66. Creamer and Rankin each had 68s.
Laura Davies used three late birdies for a 65 and was at 10-under 203 along with Young Jo (66).
Sung Ah Yim was at 204, with 2000 Farr winner Annika Sorenstam leading the pack at 205, four shots back of the leaders.
Last year's LPGA rookie of the year, Creamer hasn't won in more than a year. Rankin is winless in her 2 1/2 years on tour.
Sunny skies and high humidity greeted the golfers for the second day in a row. The heat helped to lower floodwaters that turned the tiny Ten Mile Creek that meanders through the course into a raging torrent.