NFL, CMA among those at Okla. weather conference

Digby told The Associated Press he is working on expanding its guidelines to Australia, with international music tours in mind.

"Last year, when I first announced this initiative, I thought I was throwing a hand grenade in the room," he said with a laugh. "The entire industry — once they figured out what we were trying to do, they have embraced the project."

Event organizers and managers said they're taking Digby's advice to heart.

"We're going to go back and adapt the trigger plan," said Vilma Salinas, the Country Music Association's senior manager of projects. The CMA Music Festival at Nashville, Tenn., which draws 200,000 fans, has emergency plans in place, but could benefit from more precision on when people need to move, she said.

"The biggest thing is who gets to make the call," she said. "Country music fans are die-hard fans. We need to be as clear as possible."

As tornado expert Chuck Doswell told the conference, severe weather is relatively rare but inevitable.

"Imagine the Indianapolis 500 ... with those hundreds and hundreds of RVs with nowhere to go," Doswell said. If a tornado such as one that killed 158 in Missouri two years struck an event that did not have a severe weather plan in place, "it would make Joplin look like a Saturday afternoon picnic."