Chepstow's Coral Welsh Grand National meeting on Sunday is subject to a precautionary inspection at 8am on Saturday due to heavy rain.
The course is currently heavy, waterlogged in places and with more rain forecast ahead of the big meeting, officials felt it best to have a look.
After almost an inch of rain on Monday and Tuesday, a further 10 millimetres fell on Thursday morning. The forecast has also changed from being dry for the weekend, to the prospect of further showers.
"We've has a bit of rain this morning, which has now gone through, and in conjunction with that the forecast has changed for the weekend," said clerk of the course Keith Ottesen.
"We looked like we were going to be clear on Saturday and Sunday. The band of rain that was tracking north of us now looks like dipping down and getting us, so we are following it closely.
"We thought it would be prudent to call an inspection now for Saturday morning before declaration time so we can let everyone know where we are.
"The rain we've had was a bit more than we thought and after what we've had it raises our concerns if we do get rain.
"Saturday and Sunday were looking clear but it now looks as though it's going to rain and it is not going to be completely dry between now and Saturday.
"The forecast is for light patchy rain all day then showers on Saturday followed by the possibility of a band of rain coming through on Saturday night into Sunday morning.
"We are hoping that rain takes a different track. If we are clear on Saturday and Sunday, we'll be fine, but because we're getting that information about rain and after that extra bit of rain this morning, we have got some concerns.
"It's a precautionary inspection because we need to re-group on Saturday."