The Storm Prediction Center is adding two threat levels to its U.S. weather outlooks so people aren't surprised by really bad storms on days with just a "slight risk" of tornadoes, hail or high winds.
Beginning Oct. 22, forecasters can say whether slight risk days are "enhanced" or "marginal."
Other categories remain, including "high" and "moderate."
The Norman, Oklahoma-based center proposed the change after finding that some days had conditions worse than a "slight risk" but not as bad as a "moderate risk."
The center evaluates the chance of threatening weather daily, then generates a map showing where it could strike.
The National Weather Service said Monday that more than 80 percent of people who responded during a comment period favored changes.
But some feared the maps will be confusing.