Tropical Storm Helene formed Tuesday in the Caribbean Sea and could strengthen into a major hurricane while moving north toward the U.S., forecasters said.

Tampa Bay residents should prepare for potential hurricane conditions within 48 hours, officials say, with Tropical Storm Helene expected to become a hurricane in the Gulf of Mexico Wednesday. A stretch of Florida’s west coast including Pinellas and Pasco counties is under a hurricane watch.

A storm system could soon become Hurricane Helene, and strike Florida later this week with winds as high as 115 mph.