The top 30 after the competition in St. Louis will play in the Tour Championship at East Lake outside Atlanta, Georgia, next week.
Ahead of the event, Alex Norén - who has never played in the Tour Championship - needed to finish no worse than 17th to have any chance of climbing into the top 30.
After two tentative days, the 44-year-old found his game on Saturday. Norén was level par after seven holes, but then birdied five holes to finish the day five under par. He is also five under overall and tied for 15th place heading into Sunday's conclusion.
Ludvig Åberg, who has already qualified for the Tour Championship, is also five under overall.
Leading the competition is Wyndham Clark at 17 under.
