The Washington PostDemocracy Dies in Darkness

Flash flooding in Mississippi inundates streets and prompts rescues

The highest totals seen in the past day or two are at least 1-in-200-year or 1-in-500-year rainfall events

The high levels of rain recorded in Mississippi on Aug. 24 are only seen in the region once every few hundred years. (Video: The Washington Post)

The summer of big flash floods strikes again.

Up to a foot of rain fell across parts of central Mississippi on Wednesday, leading to life-threatening situations and numerous rescues. The intense rain swept away portions of a highway, while floodwaters partially submerged cars and trees.

Multiple rare flash-flood emergency warnings were issued at midday Wednesday along Interstate 20 in central Mississippi, including in the capital city of Jackson. I-20 was closed in spots east of the city, according to the Transportation Department.

Additional major rainfall totals occurred in parts of western Alabama, as flash-flood warnings briefly stretched from that state to Louisiana. The heaviest rain slid east. The National Weather Service office in Mobile, Ala., stated that the wet pattern will persist through at least Thursday evening and may result in heavy rain and flooding issues.

“Doppler radar indicated thunderstorms producing heavy rain across the warned area. Between 6 and 10 inches of rain have fallen,” wrote the Weather Service in Jackson. “Additional rainfall amounts of 2 to 4 inches are possible in the warned area. Flash flooding is already occurring with numerous roads flooded and homes threatened or inundated.”

A handful of confirmed rainfall totals over the past 24 hours near and east of Jackson include 8.89 inches in Forest, 8.20 inches in Wiggins and 7.98 inches in Goshen Springs. Near Walnut, Miss., over 15 inches has fallen in two days. Given radar estimates and the reality on the ground, some totals may exceed these 24- and 48-hour values.

The highest totals seen in the past day or two are at least 1-in-200-year or 1-in-500-year rainfalls, rare events that have only a 0.5 to 0.2 percent chance of occurring in any given year.

A full analysis may show some locations end up with an even rarer rainfall. This flooding event could be the sixth 1-in-1,000-year rainfall in recent weeks in the United States. In other words, it has a 0.1 percent chance of happening in any given year. Increased moisture availability in a warming world is a factor in these events.

Five 1,000-year rain events have struck the U.S. in five weeks. Why?

Widespread flash flooding and rescues were underway in places such as Canton, on the northeast of the Jackson metro area, and Brandon, on the eastern edge. Numerous road closures and power outages were also reported.

At least 42 residents of a nursing home in Brandon have been evacuated because of rising waters. Rankin County, which includes Brandon, deployed three water rescue vehicles, two regular boats and one airboat, Sheriff Bryan Bailey said.

In Canton, some people were dealing with flooding for the second time in a month. Crisco Creek topped its banks, inundating nearby parks and forcing some residents from their homes.

The Mississippi Emergency Management Agency, along with other state officials, requested that people stay off roadways in the areas with flooding.

Wednesday’s rainfall is the latest in a slew of similar events over recent weeks across the country. Triggered by low pressure along a stalled frontal boundary, plentiful moisture from the Gulf of Mexico was sitting in wait.

The region was under a moderate risk from the Weather Prediction Center, and flash-flood watches were up before heavy rain began.

Despite warnings leading up to and during the event, rainfall totals of multiple inches per hour and 8 to 12 inches or more over a short period are bound to cause flooding. This is especially true on soil already saturated by previous rains.