Major and secondary routes were threatened by rising waters, particularly the Susquehanna River, which is forecast to eventually rise to 29 feet in Harrisburg on Friday, six feet above what is consider major flood stage.
PennDOT has closed hundreds of roads across the eastern half of the state. Department spokesman Steve Chizmar urged caution even if waters receded by Saturday, as inspectors still needed to check on the structural integrity of roads and bridges.
"It's going to be challenging at best to get into Penn State," Chizmar said Thursday night.
A sellout crowd of 108,000 was expected at Beaver Stadium for the showdown between the third-ranked Crimson Tide and 23rd-ranked Nittany Lions.
Deluges in State College subsided by Wednesday morning, though days of rain earlier in the week still left several grass lots used too saturated for parking. About 2,500 vehicles will need to be redirected to off-site lots, with free shuttle service provided.
The vast majority of fans will not be affected by the changes, though Penn State urged attendees to carpool or use shuttle services to the game. Patrons were urged to leave RVs at home.