WASHINGTON - US southeastern states Mississippi and Florida on Saturday separately declared emergency ahead of subtropical storm Alberto's heading toward Gulf Coast, threatening to bring heavy rainfall and flash floods.

Florida Governor Rick Scott said Saturday morning that his declared state of emergency covers all 67 counties to "prepare for the torrential rain and severe flooding this storm will bring."

Mississippi Governor Phil Bryant also announced a state of emergency and an order "making the National Guard and other resources available should they become necessary."

Storm Alberto is forecast to move northward into the Gulf of Mexico over the weekend, with its center passing west of Cuba, the Florida Keys and Florida's mainland, and setting its sights on eastern Louisiana, the Florida Panhandle and the coasts of Alabama and Mississippi, according to an ABC News report.

Since Alberto is a lopsided storm, the most notable impacts will be to east of the center of circulation. Heavy rain is expected to affect much of Florida and the Gulf Coast later this weekend, said the report.