Dangerous Thunderstorms in Texas Begin Southern Severe Weather Outbreak

“Several tornadoes, including the possibility of a few strong tornadoes, along with very large hail and damaging winds, are expected this afternoon through tonight, especially across parts from central/east Texas to western Louisiana,” the National Weather Service writes. Storm Prediction Center.

A tornado watch is in effect for much of eastern Texas from roughly Dallas to San Antonio through 10 p.m. Monday, affecting nearly 14 million people.

On Tuesday, an acute risk of severe thunderstorms shifts to the deep south. The Storm Prediction Center warns that a “regional outbreak of severe weather, including potential for strong tornadoes, is possible.”

By Wednesday, storms will enter the forecast for parts of the southeast and south of the Mid-Atlantic. While the risk of severe weather should decrease somewhat, a few tornadoes are still possible.

Amid the damaging thunderstorm threat comes an equally formidable flood hazard. Parts of Texas and Louisiana can expect widespread flash flooding and excessive rainfall on Monday, and that danger will expand through Mississippi, Alabama and western Georgia on Tuesday. More than two inches of rain could fall in some places.

The multi-day event marks the first classic spring episode of severe weather of 2022, but overarching weather patterns favor continued active weather. Another round of strong to severe thunderstorms could enter the equation to round out the month.

A lobe of cold air, low pressure and high-altitude spin — known as a “shortwave” — is ejected eastward across the southern plains. Cold air acting over mild, moist air near the ground will create an “unstable” atmosphere that allows the surface air to rise.

At ground level, a low surface pushes through the southern Texas Panhandle and Hill Country. The low’s counterclockwise vortex stirs southerly winds, dragging a filament of air from the Gulf of Mexico. That will fuel thunderstorms.

Those storms will erupt along a “dryline,” the leading edge of dry air from the desert’s southwest penetrating the aspirated air to the east. A fierce dive in the jet stream meanwhile causes an increase in wind shear, or a change in wind speed/direction with height. This allows storms to spin and become rotating supercells.

Dangerous Monday in Texas

A level 4 out of 5 severe weather risk is a bull’s eye in east central Texas, and includes Austin and College Station. Around it, a level 3 risk out of 5 includes Houston and Dallas. A broader “light risk” is for San Antonio and Wichita Falls.

While morning storms have swallowed some of the instability, or fuel, for afternoon storms, there is still enough to support the rapid development of thunderstorms along and west of Interstate 35 between just south of Dallas and near San Antonio through Monday evening.

“A few longer-trail supercells could start over parts of central TX late in the afternoon and move northeast, posing a threat of tornadoes and very large hail, with some strong tornadoes possible,” the Storm Prediction Center writes.

Evening commutes can be severely disrupted as thunderstorms with destructive winds, hail bigger than golf balls and perhaps a few tornadoes working eastward.

Tornado risk will be maximized with all storms able to remain isolated and discrete, away from neighboring cells. This will most likely be early in the storms’ life cycle. After that, they will transition into a squall line overnight with continued wind and tornado risk as the rough weather shifts to the deep south.

Devastating storms likely in the deep south on Tuesday

Tuesday has a level 4 out of 5 severe weather risk. In the red zone, Baton Rouge and Jackson, Hattiesburg, Pearl and Clinton, Miss New Orleans and Lake Charles, La., have an increased level 3 risk.

A cluster of thunderstorms will leave Texas around dawn and move across the Sabine River along the Louisiana border. The storms may have coalesced into a QLCS, or “quasi-linear convective system,” at the time. That is a squall line with embedded circulations. Harmful straight-line winds and a few high-speed tornadoes are likely.

Clouds ahead of the front will counteract the warming of the day and the build-up of instability, but extreme shear will allow any storms to rotate.

As the day progresses, that squall will move to the east. Before that, advection of warm air, or a conveyor belt of warm air from the south, can result in widely distributed supercells that are rotating thunderstorms. Those have the highest risk of significant tornadoes, some of which could be on the ground for extended periods of time. Some areas may have multiple severe weather events, with one or two supercells and then the squall line.

“You have to have a plan to get out of your [manufactured] go home and go to the shelter BEFORE the tornado warning is issued,” tweeted Stephen Strader, a hazard researcher at Villanova University who has published research on communities vulnerable to severe weather. “Know your shelter locations. Get a weather radio to wake up when you sleep.”

Thunderstorms will move across the southeast by mid-week. A wide swath of the Florida Panhandle through Georgia and the Carolinas and Southern Virginia will be in the “warm sector” of approaching low pressure ahead of the front. Raleigh, Charlotte, Wilmington, Charleston, Savannah, Atlanta and Tallahassee are included in a level 2 of 5 light risk. Sporadic gusts, isolated hail and some tornadoes are possible.

In addition to the threat of a tornado, flash flooding will also become an increasing threat as the multi-day stretch of storm unfolds.

Much of the mid-south and deep south will end with widespread rain of 2 to 4 inches, with a shot from outside an isolated total of 6 inches. East Texas, northern Louisiana, southern Arkansas, western Tennessee, and northern Mississippi and Alabama have the highest probability of flooding.

The National Weather Service signed moderate risk zones for those areas Monday and Tuesday, writing “accumulations of 3 to 6 inches will certainly be possible, with highly isolated larger amounts embedded as well.”

The rainfall can cause flooding in cities and small streams and, in high rainfall, also cause some flash floods.

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