Tropical Storm Karen was stationary in the Gulf of Mexico for several hours late Saturday with the center expected near or over southeastern Louisiana overnight into Sunday, forecasters said.
The storm is expected to bring rain and some coastal flooding before it moves just south of the Gulf Coast from Alabama to the Florida panhandle Sunday night and Monday, according to the National Hurricane Center.
At 0001 GMT, Karen was located about 115 miles (185 kilometers) south-southwest of Morgan City, Louisiana, packing maximum sustained winds of 40 mph (64 km/h).
A tropical storm warning remained in effect from Grand Isle, Louisiana, to the mouth of the Pearl River. All other warnings and watches have been dropped.
"Karen is expected to weaken to a tropical depression on Sunday and become a remnant low by Monday," the Miami-based NHC said.
The storm surge "will be accompanied by dangerous waves," with surge-related flooding dependent on the "timing of the surge and the tidal cycle."
Karen is forecast to drop between one to three inches of rain (up to 7.6 cm) over the central Gulf Coast and southeastern US region through late Monday.
"Isolated storm total amounts of six inches (15.24 cm) are possible," the NHC said.
Florida Governor Rick Scott said Saturday that 12 counties were under a local state of emergency and urged residents not to become complacent because the storm was weakening.
"As Tropical Storm Karen continues to disorganize, families should still use today as an opportunity to get ready," he said in a statement.
"Communities along the panhandle are expected to experience heavy rains, and storm surges are predicted for our coastal regions."
Oil prices rose Friday on falling production as companies evacuated staff from sensitive refining and production areas along the Gulf Coast.
On Thursday, President Barack Obama was briefed on disaster preparations and his administration recalled emergency workers who had been told to stay home due to a government shutdown linked to a bitter budget dispute.