Portions of the Gulf Coast are entering day two of relentless rain Wednesday, increasing the odds of flash flooding for millions.
Roughly 9 million people are under a flood watch, including the Houston metro area and parts of Louisiana.
“Slow-moving thunderstorms within a moisture-rich environment will be capable of containing intense rainfall rates and lead to the threat of flash flooding through early Thursday,” warned the Weather Prediction Center. “Urban regions and flood-prone areas will be most at risk to rapid onset flooding, as well as locations that possibly experience over 5 inches of rain.”
A slow-moving area of low pressure will meander to the north through the day Wednesday, leading to the slow nature of these downpours and increasing the risk of flooding.
The prediction center has expanded the Level 3 out of 4 moderate risk of flash flooding for much of southeast Texas and western Louisiana, including Houston and Beaumont in Texas, and Lake Charles and Shreveport in Louisiana.
The biggest concern will be where the heaviest downpours set up and have little movement.
These are called “training storms.” They dump tremendous amounts of rain on the same area, causing flash flooding and dangerous scenarios in an instant.
The Houston area could see an additional 2-4 inches of rain Wednesday, after as much as 4 inches of rain fell Tuesday in some areas. Some isolated locations could get up to 5-7 inches around the heaviest downpours.
Farther north, near Shreveport, the heaviest downpours will begin to move in later Wednesday.
“Bottom line up front: A more significant rainfall event appears to be taking shape for later today and tonight,” the National Weather Service office in Shreveport said. “The flooding concerns have ratcheted up significantly over much the region.”
The Ark-La-Tex region could see widespread rainfall amounts up to 3 inches, but isolated locations could pick up more than 5 inches.
A Level 2 out of 4 slight risk of flash flooding expands north into Arkansas and includes Little Rock.
In addition to the flash flooding, there is also a concern for severe storms. A few isolated tornadoes and damaging wind gusts will be a possibility as these storms meander to the north.
The bulk of the storm activity should be wrapping up along the coast Wednesday evening and continue into Thursday morning for areas to the north.
By Thursday evening, much of the flood potential will be over, with just lingering storms through the end of the week.