Rare flash flood emergencies were declared in Lake Charles and parts of Baton Rouge, La., Monday afternoon and night after more than a foot of rain fell, inundating streets and sending water gushing into homes and businesses.
The National Weather Service Weather Prediction Center highlighted parts of Texas, southeast Oklahoma and much of Louisiana as having a “moderate risk” of flash flooding and excessive rainfall on Tuesday and Wednesday. About 30 million people are under flash flood watches, including those in cities like Dallas-Fort Worth, Austin, San Antonio, Waco, Oklahoma City, Little Rock, Ark., and New Orleans, Baton Rouge and Lake Charles, La.
Rainfall could last into the weekend in some spots, with widespread 6-to-12-inch totals and a chance that some places could see as much as 15 inches.
Serious flooding has already occurred in Louisiana and Texas
Lake Charles, La., a city ravaged by two hurricanes, Laura and Delta, in 2020, received 12.49 inches of rain on Monday, including 6.35 inches between 1 p.m. and 3 p.m. as rainfall rates topped three inches per hour. Vehicles became fully submerged beneath rising floodwaters as water rushed into homes and forced residents to swim to safety.
A rain gauge 2 miles south-southwest of Lake Charles measured 15.07 inches of rain.
“This is a PARTICULARLY DANGEROUS SITUATION,” warned the National Weather Service. “SEEK HIGHER GROUND NOW!”
Monday proved the third wettest calendar day on record in Lake Charles, beating out the myriad hurricanes and tropical systems that have plagued the beleaguered community over the years.
One Twitter user whose house experienced flooding wrote “after 2 hurricanes, a freeze, and now flooding … I think I’m done.”
Soils in Louisiana were already saturated from multiple bouts of excessive rainfall in the past several weeks amid a wet and active weather pattern. New Orleans has recorded upward of 2 feet of rain since the start of April, roughly three times the average.
In Baton Rouge, La., 4.33 inches of rain came down Monday at the airport, but areas just south of the state capital saw upward of 13 inches. That forced the rescue of 250 people and rendered more than four dozen roadways impassible. Vehicles were abandoned beneath overpasses near the Mall of Louisiana in Baton Rouge; one person died when their vehicle hydroplaned off a roadway and careened into a ditch.
A flash flood emergency was issued for southeastern portions of East Baton Rouge Parish at 1:15 a.m. local time Tuesday.
“Please, we beg you not to drive over flooded roads,” pleaded the Weather Service in New Orleans.
Louisiana’s Gov. John Bel Edwards (D) declared a state of emergency due to the excessive rainfall in the southwest portion of the state.
In Texas, prolific rainfall first came down Sunday southwest of Houston in the city of Ganado, where 13.5 inches was measured in parts of Wharton County.
The deluges continued Monday, including in Fannett, Tex., to the east of Houston, where an automated rain gauge measured 17.16 inches.
Nearby parts of Jefferson County saw over a foot of rain, including along Highway 87 at the Keith Lake Public Boat Launch, where 12.64 inches fell. The same area was hit hard when Tropical Depression Imelda dumped more than 40 inches of rain in September of 2019, barely two years after Hurricane Harvey unloaded as much as five feet.
⚠️ Here are the rainfall readings we have received so far from yesterday & last nights rain event.— NWS New Orleans (@NWSNewOrleans) May 18, 2021
Highest measurement was 13.09" at Bayou Manchac. There may have been higher rain between Geismar & Gonzales. #LAwx #MSwx https://t.co/N92VW1VQDv pic.twitter.com/irefTl7cIF
The Beaumont-Port Arthur area received nearly 10 inches of rain on Monday, its eighth wettest day on record.
High-end rainfall events in parts of Southeast Texas, including in the greater Houston area, are becoming considerably more common and severe thanks in large part to climate change.
Now, additional rounds of heavy rainfall are in the offing Tuesday, Wednesday and Thursday, with another six inches or more likely in many spots. The Weather Service in Houston described the situation as “weather madness.”
Contributing to the rainfall is a high pressure system over the Southeast and a low slowly meandering from near the Four Corners region to parts of Central Texas. Clockwise winds around the high are teaming up with counterclockwise flow about the low to drag and continually replenish a strip of warm, moist air across the southern Plains, much of Texas and parts of the Interstate 10 corridor all the way into Louisiana.
That fire hose of moisture will feed repeated rounds of strong to severe thunderstorms over West Texas and the High Plains, like those that brought destructive hail and tornadoes to the region on Monday. Each evening, those storms will congeal into a larger mass known as a “mesoscale convective system” before slowly marching east, lingering over some areas for hours.
The Dallas-Fort Worth Metroplex was expecting heavy rainfall to arrive by noontime Tuesday from the leftovers of tornadic storms that affected the Concho Valley on Monday.
It is tricky to predict in advance where exactly these large-scale complexes will go, but it is likely some areas could see multiple waves of two to three inch rainfalls, quickly stacking up to half a foot or more.
High-resolution computer models are bullish on the prospects for a complex of thunderstorms to sweep through Dallas, Fort Worth and Houston on Tuesday before moving east and affecting Lake Charles. On Wednesday, another storm could lash Houston with pockets of flooding likely again in Corpus Christi, Brownsville and near the Mexican border.
The Weather Service is calling for another four to six inches in Houston and Galveston, with greater amounts of six to eight inches to the northwest in Austin, Temple and College Station. A few 10 inch totals are expected.
Farther east, another eight to 10 inches is likely in Beaumont, Tex., and the Golden Triangle region into western Louisiana.
For SE TX: Flash Flood Watch in effect thru Thursday morning. Much of the area has some potential for excessive rainfall. Tuesday thru Thursday totals are expected to average 4 to 8 inches. Isolated spots could exceed 10 inches. Stay Weather Aware! #txwx #houwx #glswx #bcswx pic.twitter.com/3ww2RhLQbT— NWS Houston (@NWSHouston) May 18, 2021
Wednesday could be the wettest day of the bunch, with continued rainfall Thursday and Friday. A few additional showers are possible Saturday before a desperately needed stretch of more quiet and tranquil weather arrives into next week.