Story highlights Tropical Storm Cindy is projected to make landfall on Thursday

Up to 15 inches of rain could fall from Louisiana to Florida Panhandle

(CNN) Tropical Storm Cindy is churning slowly toward the US Gulf Coast, where millions of residents are expecting heavy rain and potential flash flooding.

At least 17 million people are under a tropical storm warning from San Luis Pass, Texas, to the Alabama-Florida border, CNN meteorologist Michael Guy said.

The storm has already claimed at least one life. A 10-year-old boy died Wednesday in Fort Morgan, Alabama, when he was struck by a log that was being carried by a wave, the Baldwin County sheriff's office said.

The storm could bring up to 15 inches of rain to parts of southeastern Louisiana, southern Mississippi, southern Alabama and western portions of the Florida Panhandle through Thursday night.

"This rainfall could cause life-threatening flash flooding in these areas," the National Hurricane Center said in its latest advisory.

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