LITTLE ROCK, Ark. — The Storm Prediction Center intends to broaden its advance warning system for severe weather after finding that days it labeled with a “slight risk” turned out to be pretty nasty.

State emergency managers say they’re already attuned to bad weather, but believe a new warning system with two additional categories, “enhanced” and “marginal,” could keep them from crying “wolf” ”“ and the public from tuning them out.

“We try to educate everybody that a tornado can pop out of thunderstorm at any time,” said Greg Flynn, a spokesman for the Mississippi Emergency Management Agency. “I don’t think it will change the way we prepare, but if it changes the mind of one person in the public, if it gets one more person to pay attention, then it’s worth it.”

When significant severe weather is forecast, the current rating system labels days as having a slight, moderate or high risk, based on the chance of tornadoes, high winds or significant hail.

Russ Schneider, the director of the Storm Prediction Center in Norman, Okla., said the agency has found over the years that some conditions warranted more than a “slight risk” label, but not quite a “moderate risk” one. The center’s default action has been to label the areas as a slight risk and advise National Weather Service offices to tell local residents and emergency managers that th

“Some ”˜slight risk’ days are really quite active,” Schneider said Thursday. “You can get some strong tornadoes those days.”

So, sometime this spring ”“ after National Weather Service administrators in the Washington area weigh in, likely in April ”“ areas at the upper end of the current “slight risk” will be said to have an “enhanced risk.” There also would be a “marginal” category for risks less than slight.

“That will not raise many eyebrows around here,” Schneider said, speaking in Oklahoma, “but could as you move into the eastern United States” where storms generally aren’t as strong. “The ”˜enhanced risk’ category will be a pretty high category if you get into the East Coast.”

Television stations throughout Tornado Alley, the Midwest and the southeast commonly show maps days in advance, asking viewers to note that bad weather could arise. And meteorologists have worked with social scientists over the years to study how people interact with weather warnings and to address any sense of complacency, Schneider said.

He cited a storm last February near Hattiesburg, Miss., that blew up on what had been a “slight risk” February day and could have been better described as an “enhanced” risk. Isolated strong storms, like one that hit near Meridian, Miss., last April and killed a man, wouldn’t have required an upgraded advisory because the threat wasn’t as broad.

The criteria are being changed only at the lower levels. Current guidelines for moderate risk and high risk days remain the same.

David Maxwell, the director of the Arkansas Department of Emergency Management, said the sense of alarm grows as forecasters go up the scale.

“We start paying attention on slight risk,” he said. By the time a moderate risk or high risk approaches, he’s holding conference calls with county emergency managers to ensure they’re prepared.

“You don’t want to have the effect of crying ”˜wolf,’” Maxwell said.

But even on slight risk days, Maxwell said, he will trust his gut and reach out if a sixth sense kicks in.

“There are some days you can walk outside and smell a tornado,” he said.

Flynn said Mississippi’s emergency managers were ready for last February’s storms because local forecasters had already put them on a heightened alert.

“Even if it’s slight, that still means something is coming,” Flynn said. “Nobody was killed because emergency managers did a great job getting everyone ready.”