COLUMBIA — Heavy thunderstorms dumped several inches of rain across the Midlands over the weekend and more is on the way — along with the threat of tornadoes.

The Columbia area has received 4 to 6 inches of rain since May 10, with the Lexington County area getting the most. Another inch of rain is expected this evening.

The final rainfall total could increase due to the sporadic nature of thunderstorms, according to Brad Carlberg, a meteorologist with the National Weather Service office in Columbia.

The Midlands is expected to continue to see heavy rainfall through May 13.

Moisture from the Gulf of Mexico and weather patterns from the Lower Mississippi Valley have led to the prolonged rain in the Midlands. As rain showers become more scattered on May 13 and 14, the threat of flash flooding will decrease, Carlberg added.

The combination of sporadic rain and warmer temperatures is causing instability in the atmosphere that could lead to “stronger cell thunderstorms” and a spin-up tornado — which forms and dissipates quickly.

The Congaree River will crest at 13.7 feet on May 15, rising more than 5 feet from its current status of 8.5 feet. This will flood the riverwalks in Lexington and Richland counties, Carlberg said.

A map showing heavy rainfall in the Southeast.

“The biggest thing to watch out for is flooded roadways,” Carlberg said. ”We use the slogan of ‘turn around, don't drown.' So if you see a flooded roadway, you don't know how deep it is, so you want to turn around and not drive through it.”