The Chevrolet 400, which will finalize the field of 12 drivers who will be eligible to compete for the 2008 series championship, is now scheduled for 1 p.m. Sunday.
"We just felt this was the right thing to do," NASCAR spokesman Jim Hunter said, adding that the decision was made after consultations with emergency officials in the area who warned that besides heavy rain, the storm was expected to bring high wind on Saturday.
"Tomorrow's going to be a tough day," track president Doug Fritz said, based on the forecasts. "Sometimes there's hope and sometimes there's not. This is one of those moving targets. ... We're still looking for two days of great racing, all crammed into one now."
The Nationwide Series race scheduled for Friday night was moved to Sunday at 7 p.m.
NASCAR said the field for both races will be set based on driver's standings and that the garage will be closed and the cars impounded from Friday night until 7:30 a.m. on Sunday.
The postponements are particularly bad news for rookie sensation Joey Logano, who was scheduled to make his debut in NASCAR's premier series driving for Joe Gibbs Racing. Because qualifying was washed out, he didn't get a chance to make the field.
"I can't change the weather, so I just go with it," said Logano, who will replace the departing Tony Stewart in Gibbs' No. 20 next season.
Fritz said the hundreds of motor homes already in place on the grounds of the track will be allowed to stay, even though there are no activities planned at the track on Saturday.
It was the number of fans that come from far away that made the decision hard, he said.