MIAMI -- Florida Gov. Rick Scott declared a state of emergency Saturday for all 67 counties ahead of Subtropical Storm Alberto. He said in a tweet he made the declaration "to ensure our state has the resources they need to keep their families safe and prepare for the torrential rain and severe flooding Subtropical Storm Alberto will bring."

At a briefing at the state emergency operations center in Tallahassee, authorities urged Floridians to take the storm seriously.

Wes Maul, the state's emergency management director, said the timing of the storm is uncertain, but the entire state will feel the effects. Swelling riverbanks, tornadoes and localized flooding are possible.

Flood warnings and rip current advisories are in effect across the state. See the most current advisories in your county here - https://t.co/pGryT4ker3 — Rick Scott (@FLGovScott) May 26, 2018

The storm, moving slowly through the Caribbean Sea, is threatening to bring heavy rainfall, mudslides, and flash floods to parts of Mexico, Cuba, Florida and the U.S. Gulf Coast this weekend.

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Alberto -- the first named storm of the 2018 hurricane season -- was continued roiling toward parts of coastal Mexico and Cuba with rip currents and dangerous surf on Saturday. Both countries issued tropical storm watches for portions of their coastlines, with rain totals in some isolated areas of up to 25 inches.

A general view shows an empty beach as subtropical storm Alberto approaches Cancun, Mexico, May 25, 2018. STRINGER/REUTERS

U.S. forecasters followed suit by issuing a tropical storm watch for parts of the Gulf Coast from the Florida Panhandle southwest of Tallahassee to the New Orleans metropolitan area.

Florida Gov. Scott said the Florida National Guard has 5,500 guard members available for deployment if needed.