A Texas-size onslaught of wild weather is set to slam the Lone Star State this week, with the potential for very large hail, destructive wind, tornadoes and major flooding.

Areas near Dallas and Houston were under flash-flood warnings for a time as heavy thunderstorms rumbled through Texas on Sunday. That’s just the start of a waterlogged week on tap for much of Texas and parts of Louisiana, Oklahoma and Arkansas, with repeated rounds of excessive rainfall likely to bring the threat of localized urban and flash flooding. Flash-flood watches stretch from Oklahoma City through Dallas and Houston to southwest Louisiana.

A flash flood emergency, the most severe flooding declaration, was issued on Lake Charles, La. Monday afternoon until 4:45 p.m. local time due to torrential rainfall. “This is a PARTICULARLY DANGEROUS SITUATION. SEEK HIGHER GROUND NOW!,” the National Weather Service warned.

Lake Charles Airport had received more than a foot of rain through late afternoon, its third wettest day on record.

Social media footage showed homes, roads and businesses engulfed by floodwaters in the same communities slammed by both hurricanes Laura and Delta in the fall.

“The flash flooding throughout Lake Charles and Southwest Louisiana is dangerous and potentially life threatening,” tweeted La. governor John Bel Edwards (D).

The excessive rainfall comes in addition to the potential for severe storms from western Louisiana into the Southern Plains. A tornado caused damage in North Dallas on Sunday afternoon, hitting some of the same homes struck by a destructive tornado in October 2019. The Weather Service received more than 120 reports of severe weather on Sunday, including more than 90 instances of large hail.

Rainfall forecast

More than six inches of rain is on the way for many along the Interstate 35 corridor in Texas and eastward, with the risk of excessive rainfall extending to other cities such as Galveston, Waco and Austin. It’s not out of the question that a few locales pick up double-digit rainfall totals by the end of the workweek.

A whopping 17 inches of rain had fallen in Fannett, Tex., about midway between Lake Charles and Houston, as of Monday afternoon. 13.5 inches of rain came down Sunday in Ganado, Tex., just southwest of Houston in Wharton County. Parts of nearby Jackson County picked up to 9.61 inches, with Bay City in Matagorda County reporting 5.39 inches.

The Weather Service’s Weather Prediction Center has included areas from the Dallas-Fort Worth Metroplex northeastward into southeastern Oklahoma in a Level 3 out of 4 “moderate risk” of flash flooding and excessive rainfall for Tuesday and Wednesday.

“Given the impressive amount of moisture forecast the next three days over the Southern Plains, an extensive area will likely see numerous areas of impactful flooding ... which includes several urban/metropolitan areas,” the agency wrote Sunday.

“We find ourselves in a very conducive environment for showers and thunderstorms each day across Southeast Texas,” the Weather Service’s office in Houston echoed in a forecast discussion. “The Tuesday night through Thursday morning stretch likely carries the highest threat for flooding rains ... please make it a point to be aware of the weather situation this week and keep up with the latest forecast information.”

Forecasters were growing increasingly concerned and dismayed at the projection, evidenced by levity sprinkled in their discussion.

“To quote the scientist who must predict the future, ‘Sometimes science is so difficult it makes me sad,’ ” read the discussion.

The forecast is tricky because of the chaotic behavior of thunderstorms, but there is confidence in multiple such systems affecting western Louisiana, eastern Texas and Oklahoma. A broad 2 to 4 inches of rain is likely in central and eastern Oklahoma, with a general 3 to 6 inches in the eastern half of Texas and western Louisiana and 4 to 8 inches in southeastern Texas, including Houston. A few places could top 10 inches.

It appears that Wednesday will be the wettest day of the bunch in Houston, with continued heavy rain Thursday before a drying trend on Friday.

High-end rainfall events are twice as common in Houston nowadays compared with in the 1970s, in large part because of climate change; continued urban sprawl, development and land use have caused the city’s vulnerability to rainfall to skyrocket, resulting in frequent high-impact flooding.

Risk of severe storms with large hail and tornadoes

Rounds of strong to severe thunderstorms are expected Monday and Tuesday afternoons, with more potentially dangerous thunderstorms likely later in the week.

The National Weather Service Storm Prediction Center highlighted parts of western Texas as being under a Level 4 out of 5 risk of severe weather, driven mainly by the potential for large to giant hail. A few instances of baseball- to softball-size hail are expected in the corridor between Lubbock and Abilene, Tex.

A similar environment will support storms on Tuesday and Wednesday.

After initial isolated storm development on Monday, which would present a risk of damaging winds, large hail and tornadoes, storms are expected to merge into clusters by late each afternoon around sunset. Eventually, they may bow into arcing squall lines capable of producing strong wind gusts, prolific lightning shows and a quick 1 to 2 inches of rainfall.

Those “mesoscale convective systems” have a tendency to race east or southeast at night, lasting until their demise the following morning.

Contributing to the active pattern is high pressure located in the eastern United States; clockwise winds around it are inducing a moist flow out of the south and southeast, pumping humid air northward. Those southerly winds are being reinforced by counterclockwise winds surrounding stagnant low pressure to the west. That low is also bringing very low temperatures aloft, supporting continued thunderstorm activity.

Additional rounds of severe weather are expected across western and Central Texas over the coming days, but predicting where storms will occur often depends on factors influenced by previous days’ storms. The wet pattern in eastern areas, meanwhile, should finally relent by the weekend.

Sunday’s storms were picturesque, thrilling storm chasers

The weekend featured rounds of severe thunderstorms from Texas Hill Country and the panhandles north through the Colorado Front Range and adjacent western Kansas. At least one highly photogenic storm on Sunday dropped a picturesque tornado about 50 miles northwest of Lubbock near the town of Amherst, dazzling storm chasers.

Here are some breathtaking images:

Jason Samenow contributed to this article.