The Bureau of Meteorology is forecasting an 80 percent chance of showers in the late afternoon and evening with a chance of a thunderstorm.
Rain has already mixed up the grid for the Great Race after a shower hit mid-qualifying before another heavy downpour arrived ahead of the Top 10 Shootout.
“The car needs to be good in both the dry and wet,” Coulthard told Speedcafe.com of the race ahead.
“We will have to come to some agreement as to how we will set the car up and hopefully be there at the end.
“A lot of it is going to be thinking on your feet with the weather. It will rain at some point, it could be a wet-dry-wet-dry race. It could be one of those days.
“It throws it wide open. It could have the potential of being a race where it is decided by the person who is on the right tyre at the right time.
“Knowing how much rain and when we are going to get it is going to be the key to being successful.”
The Shootout provided drivers with their first taste of the Mount Panorama circuit in wet conditions since it was resurfaced ahead of last year's event.
“It certainly behaves differently to what the old surface did in the wet,” said Coulthard's team-mate Jason Bright, whose BOC Holden will start third.
“I think we are in for a day where there could be a few showers and that usually makes a pretty interesting day at Bathurst.
“You always feel like you're on the wrong tyre at the time because it can be wet at the top and dry at the bottom. We've got a very mixed up grid. I think we are in for a big day.”
Mixed conditions could play into the hands of the more experienced campaigners, such as pole-sitting co-driver Dean Canto.
“I have driven in the wet before here and it doesn't really bother me,” he said.
“It's just going to be one of those things. There is no give here. If you have a little moment, it's a big moment.
“As a co-driver I probably won't be driving as hard as the main guys. Usually when I'm in the car its not at the end.
“Dave (Reynolds) is third in the championship as well so I've got to keep that in mind.”