The Principality Stadium roof will be partially open for Wales' Autumn Series finale against Australia on Saturday because of a fault in the closing mechanism.
Heavy rain is forecast throughout the afternoon in Cardiff.
But the Welsh Rugby Union (WRU) says the stadium's retractable roof is not functioning properly, meaning there will be a three-metre wide opening.
The issue cannot be fixed before the game's 15:15 GMT kick-off.
"The computer software which controls the roof mechanism has encountered a mechanical fault which could take several hours to repair, and therefore cannot be resolved before kick-off," a WRU statement said.
"For this reason the roof will remain with its current three-metre gap for this afternoon's match."
Wales go into the game in need of victory amid pressure on head coach Wayne Pivac's position.
Phone: (800) 737. 6040
Fax: (800) 825 5558
Website: 
Email: 
