Cardiff - Wales coach Warren Gatland has maligned France's decision to leave the Millennium Stadium's retractable roof open for Saturday's final Six Nations match.
With Wales going for the Grand Slam after having gone unbeaten in their opening four matches, a fervent atmosphere is expected from a sell-out 74 500 crowd.
But with rain forecast on Friday and Saturday, Gatland said the decision to leave the roof open was indicative of France's likely gameplan masterminded by coach Philippe Saint-Andre.
"They're going to be very, very physical," the New Zealander said.
"The roof's open and I think they picked an old, tough forward pack. It's not going to be a pretty game from them so we have to expect that tough physical confrontation they're capable of bringing to the Millennium Stadium.
"It's going to be tough up front. And if the weather conditions are a bit showery and the roof's open and it's raining, the side that they've picked will likely be more physical than ... more open."
Gatland added: "Having coached against him in the past, Philippe is relatively conservative in the way he approaches the game. He's very pragmatic in terms of set piece and scrums and line-outs and big physical players.
"I don't think he'll care too much about the type of rugby they'll play. His whole focus is trying to win the match."
Currently, the decision on whether to leave the roof closed or open lies at the mercy of the visiting team, with both teams having to agree on whether to close it.
"It's okay if it's a nice day" to leave it open, said Gatland.
"It's something maybe as a Welsh rugby union we need to make some representation to the IRB because if it's our stadium and we have the ability to open and close the roof, then maybe we should be the team who decides that.
"I'd hate to think that on Saturday if it's pouring down with rain we've got the chance to close the roof and potentially make the game less open or attractive because the rain may affect it.
"We all have a responsibility not just to the broadcaster but the public and the game as whole to make it as attractive as possible and if that means closing the roof when it's wet, then we should be able to do it.
"But the rules are the rules and both teams have to agree and if one team decides they want the roof open, as Italy did in the last game, unfortunately it stays open."
Gatland insisted that the Wales team were trying to have as normal a week as possible in the run-up to the Grand Slam decider.
"This week's just been a normal week training. We've carried on training, kept within ourselves as a team, tried not to take too much on this week in terms of building up the hype, that will take care of itself," he said.
"We're trying to stay calm, not to use emotional imagery which can sometimes catch a team out."