The Latest on severe weather across the United States (all times local):

11:30 a.m.

A tropical storm warning is in effect for a large stretch of Florida's Gulf coast from Indian Pass in the northern Panhandle to Englewood south of Tampa.

The National Hurricane Center in Miami issued the warning before noon EDT Sunday. Tropical storm conditions — including heavy rain and strong wind — are expected to reach the area under the warning by Monday afternoon.

The storm — moving north at about 8 mph (13 kph) — is expected to become a tropical storm before reaching the Florida coast. Maximum sustained winds are near 35 mph (55 kph).

Isolated tornadoes are possible Monday afternoon in parts of Florida and southern Georgia.

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Hurricane officials say a storm in the northwestern Caribbean Sea could develop into a tropical storm before hitting Florida with flooding rain.

The National Hurricane Center said a hurricane hunter plane will investigate the storm near Mexico's Yucatan Peninsula Sunday afternoon. It already contained thunderstorms and near tropical storm strength winds.

There is a 90 percent chance the weather system could develop into a tropical depression or named storm by Sunday night or Monday morning.

Regardless of development, heavy rains and flooding are expected in the Yucatan Peninsula, western Cuba, the Florida Keys and Florida's Gulf Coast over the next few days.

Florida Gov. Rick Scott planned a briefing with state emergency management officials Sunday afternoon.

Sand bags were being distributed to residents in St. Petersburg, Tampa and nearby cities.