Thunderstorms popping up near each other and tracking back to join previously formed storms in Ascension and East Baton Rouge parishes Monday morning dumped heavy rain, causing flash flooding, with parts of Ascension Parish especially hard hit, the National Weather Service said. 

And there's more to come.

A flash flood watch for southeast Louisiana, including Baton Rouge and surrounding areas, has also been issued until 7 p.m. Tuesday.

The storms on Monday were unusual, to say the least.

Kevin Gilmore, a meteorologist with the National Weather Service office in Slidell, said the office send out a flash flood watch early Monday morning for the southeastern Louisiana region, after the 6 a.m. launch of the daily weather balloon — which also goes up at other times throughout the day — detected heavy moisture in the atmosphere.

"The showers started developing at the morning rush hour, then really started blossoming around that time," Gilmore said. 

In a process called "back building," one storm would develop upstream of another one, stoked by rain-cooled air, "then come back over the other storm, causing heavy downpours in a short amount of time, until — boom — you've got spot flooding," he said. 

Close to 4 inches of rain fell in areas of north Baton Rouge on Monday. Other parts of the city that saw more than 3 inches of rain included the Oak Hills Place and Westminster neighborhoods. 

The rain fell unevenly in the parish, with the National Weather Service gauge at Baton Rouge Metro Airport reporting just under an inch of rain through 4 p.m. Monday. 

Firefighters helped residents in the St. Gerard Avenue area in north Baton Rouge get to safety after their homes had taken on water, said Curt Monte, spokesman for the Baton Rouge Fire Department.

High water also forced the closure of 16 streets in Baton Rouge.

Monte said firefighters helped several people get out of their stalled cars to safety after the drivers had attempted to go through high water at three intersections in Baton Rouge: Florida Boulevard at Wooddale Boulevard; Coursey Boulevard at Lake Sherwood Ave., and Greenwell Springs Road at North Sherwood Forest Drive.

Firefighters, with the help of Baton Rouge Police, barricaded intersections, during and following the incidents, he said. 

It's important, Monte said, to remember the words "Turn around, don't drown" when facing a flooded road.

By 1 p.m. in Ascension Parish, Sorrento received close to 5½ inches of rain, portions of Prairieville and Burnside also got more than 5 inches, and Gonzales registered 4 inches, the National Weather Service reported. 

By 3 p.m., the Ascension Parish Sheriff's Office had announced closures of 14 roads due to high water and the Ascension Parish government had activated its large Marvin Braud pumping station in McElroy Swamp and its Sorrento pumping station in Conway Bayou.

For a list of road closures in East Baton Rouge, log onto https://city.brla.gov/emergency/.

Information on road closures in Ascension is available at www.facebook.com/AscensionSheriff.

Sandbags in East Baton Rouge Parish are available at the following BREC facilities: Alsen Street Park, Cadillac Street Park, Doyles Bayou Park, Harley-Vey at Gardere Park and Memorial Stadium. Sand not bagged up can be found at the BREC Lovett Road Park. 

Sandbags in Ascension Parish are available at:

  • Butch Gore Park, Harry Savoy Road, St. Amant.
  • 7th District Fire Dept. Roddy Road, Gonzales.
  • Fire Station No. 1, Hwy 61, Gonzales.
  • Prairieville Fire Dept., Hwy 73 at Miller Road, Prairieville.
  • Jackie Roberson Park, Coco Road, Geismar.
  • 5th Ward Fire Dept. Hwy 22 at Astroland subdivision, Darrow.
  • Stevens Park, Cannon Road, St. Amant.
  • Parish Department of Public Works West, 725 Church St., Donaldsonville.

Email Ellyn Couvillion at ecouvillion@theadvocate.com.