Severe thunderstorms and tornadoes struck the central High Plains and southern Plains on Tuesday, causing damage in Texas and Oklahoma before merging into a line of thunderstorms that marched east. The instigating cold front was unleashing flooding Wednesday in the Ozarks and may bring a second round of damaging winds and hail into Texas.

The National Weather Service Storm Prediction Center hoisted a Level 3 (out of 5) alert for enhanced risk of severe weather for much of Texas, warning that hail the size of softballs could accompany tornadic thunderstorms that will bubble up during the afternoon heat.

Farther north and east, a flash-flood risk spans from the Mexican border through the Ozarks to the mid-Mississippi Valley. That risk will expand eastward Thursday.

Wednesday’s flooding and severe storm potential

Because of ongoing heavy rain, flash-flood warnings were issued from central Oklahoma, through the northwest corner of Arkansas into southwestern Missouri on Wednesday morning as storms streamed north and east. Flash-flood watches expanded to the Indiana-Kentucky border.

An additional two to four inches of rain will be possible in some spots, with an outside chance that two-day totals for some could close in on the seven- or eight-inch mark.

“Training thunderstorms containing high rainfall rates will be possible, leading to rapid onset flooding,” wrote the Weather Service in Springfield, Mo.

As showers and embedded thunderstorms continued to trek northeast into the Midwest, the atmosphere was set to reload by early to midafternoon in Texas, producing another round of severe thunderstorms and exacerbating flood risk in areas already affected by moderate to excessive rainfall.

A Level 3 enhanced risk of severe weather stretches from roughly Abilene, Tex., to Del Rio, on the Mexican border, where new thunderstorms should begin between 4 and 5 p.m. In northern areas, storms could be strengthened by the outflow boundary, or edge of cool-air exhaust, exhaled by Tuesday’s complex of overnight storms. That will also bolster low-level helicity, or spin, allowing them to tap into rotation.

The Weather Service is warning that some of these storms, a second area of which will blossom just northeast of the Rio Grande in western South Texas, could produce hail 2 to 4 inches in diameter, as well as sporadic tornadoes and damaging winds.

By Thursday, the instigating cold front is expected to move farther east, bringing a marginal risk of severe weather from the Gulf Coast to the Great Lakes and Midwest. Gusty winds and hail are the primary concerns. The risk of flash flooding will linger from Arkansas into the Tennessee Valley.

The next chance of larger-scale severe weather looks to arrive around Monday, with signs that the pattern could favor a marked uptick in severe weather on the Plains by the second week of May.

Looking back at Tuesday

Wednesday’s heavy storms come after severe storms Tuesday dropped a rain-wrapped tornado north of Benjamin, Tex., or southwest of Wichita Falls, with a number of other funnels spinning up west of Abilene. Another damaging tornado struck overnight in Pauls Valley, about 60 miles south of Oklahoma City on Interstate 35.

Storm chasers followed the Benjamin storm to near Wichita Falls, capturing incredible views of a textbook, striated updraft — resembling a crisp but ominous mushroom cloud whirring as air spiraled inward from the south and east.

The image shows the rotating updraft of the storm. Rain-cooled air can be seen on the right feeding into it, while dry air circulating counterclockwise from the backside sculpts out a sloping birthday-cake-shaped “mesocyclone,” or area of spin. Down below, the rotation is more concentrated in the wall cloud, hanging low and looming in the middle of the mesocyclone, while a blur of rain and hail, some as large as baseballs, falls to the north on the right.

A few storms formed near the low-pressure center on the High Plains, too. They produced landspouts, or weak tornadoes, resulting from swirling winds near the surface that stretched upward to the base of a towering cloud.

The High Plains storms also poured swaths of hail in eastern Colorado and western Nebraska that left strips of white that slowly melted beneath the late-afternoon sun.

By mid-evening, storms on the southern Plains began moving along a southwest-to-northeast boundary, congealing into a messy complex that trained over, or repeatedly passed over, the same areas in North Texas and south central Oklahoma. At least 1.47 inches of rain had fallen by 9 a.m. in Wichita Falls, with 2.07 inches in Pauls Valley, Okla., where the overnight tornado hit. Some places may have seen up to four inches of rainfall.

Abilene picked up 1.76 inches of rain in a single hour, more than average for the month of April. According to Greg Diamond, a meteorologist at the Weather Channel in Atlanta, the 3.21 inches that had fallen between midnight and 9 a.m. Eastern time made Wednesday Abilene’s second-wettest April day on record. Abilene will almost undoubtedly claim top spot as additional storms roll through later Wednesday.