The flooding is the result of heavy downpours that have been thrashing the southeastern US since Wednesday, bringing record rainfalls in some areas.
The city of Mobile, for example, was walloped with 4 inches (10 centimeters) of rain Wednesday, smashing the previous record of 2.2 inches (5.6 centimeters) set in 1990.
Unseasonably warm weather this week helped stimulate the high winds, tornadoes and torrential precipitation that by today had left at least 15 people dead and dozens of families homeless.
Six people were killed in Tennessee, including three who were found in a car submerged in a creek, according to the Columbia Police Department.
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The Tennessee Emergency Management Agency said the victims were a 19-year-old female and two 22-year-old males.
One person died in Arkansas, and dozens of homes were damaged or destroyed.
Alabama Governor Robert Bentley announced today that he would visit weather-damaged areas in Coffee County.
A statement from the governor's office said that about 190 roads across Alabama were closed due to flooding.
Major flooding is forecast for Big Nance Creek, which runs through the town of Courtland in northern Alabama.
The area is about 40 miles (64 kilometers) east of Huntsville.
The creek is not expected to fall below flood stage until early Monday.
A flood warning was also in effect for the Coosa River, swollen by up to 8 inches (20 centimeters) of rain over the past week, and threatening the city of Gadsden.
The Texas and Oklahoma Panhandles are bracing for what National Weather Service forecasters are calling a "historic blizzard," but the areas under threat are lightly populated.
High winds will drive wind chills as low as 10 below zero Fahrenheit (minus 23 Celsius) and cause low visibility due to blowing and drifting snow.