Two things! A method to inform and a method to be informed.
Most events come with a warning. Primary method to inform is your cellphone. Mass text.
Alternative method could be a CB or GMRS mobile in the vehicles.
Item two. How many sources do you want? Vehicles have AM/FM radios that's one. A portable scanner is another. Truck stops sell 12v power outlet mobile televisions, that's a third, a shortwave radio receiver that's four.
Those are the only two communication requirements. Inform those who need to be informed and then a method of staying informed.