Tropical Storm Helene formed over the northwestern Caribbean on Tuesday and triggered a tropical storm warning for the Lower Florida Keys. The storm is forecast to be a major hurricane for the Florida panhandle Thursday.

Helene’s storm clouds are expected to become better organized with a more defined rotation as it enters a favorable environment.

As Tropical Storm Helene approaches, airlines are issuing waivers for those who may need to change their travel plans. Here's what to know.