The National Hurricane Center says tropical storm conditions and heavy rainfall are possible over parts of the central Gulf Coast.

The Miami-based center said Sunday afternoon that a storm system is brewing about 240 miles east-southeast of Marathon in the Florida Keys. Maximum sustained winds of the unnamed system have been clocked at 30 mph (45 kph) and the system is moving west-northwest at 15 mph.

A tropical storm watch has been issued for portions of the central Gulf Coast from the Alabama-Florida line westward to nearly Morgan City, Louisiana. The center says the system will gradually strengthen and is expected to a tropical storm by later tonight.