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Severe weather, tornado chances ramp up across South in coming week

Springtime severe weather season is about to roar to life

A tornado touches down in Selden, Kan., on May 24. (Matthew Cappucci)
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March came in like a lion when tornadoes ripped through Iowa, and, unfortunately, it looks to go out similarly. A growing risk for severe weather, including rotating thunderstorms with tornadoes, will develop late this week into early next.

The area from Texas to Florida, in particular, will need to monitor the severe storm threat over the next week or so.

Already, the National Weather Service Storm Prediction Center has hoisted a level 2 out of 5 “slight risk” for severe weather Tuesday, Friday, next Monday and next Tuesday for parts of the southern United States. Next week’s risks will probably be upgraded further as confidence grows leading up to the multiday severe weather event.

The severe weather potential coincides with a seasonal uptick in warmth and moisture over the Gulf Coast and southern Plains, the first ingredient necessary to spark convection, or shower and thunderstorm activity. April and May tend to be the most active months for severe weather and tornadoes.

Today’s risk

On Tuesday, a slight risk encompassed central parts of the Florida Peninsula, including places like Tampa, Orlando, Port Canaveral and Fort Myers. A lesser “marginal risk” covered the remainder of southern Florida north of Miami, as well as the Gulf Coast west to near New Orleans.

A weak surface low or area of storminess hung near southern Mississippi, with light southerly winds ahead of it helping to build moisture. Showers and thunderstorms will push east ahead of a weak cold front trailing the surface low. Most will be somewhat disorganized clusters, with “pulse-type” shafts of rising and sinking air that could lead to sporadic damaging winds.

An isolated tornado can’t be ruled out, especially near or just northeast of Lake Okeechobee during the first half of Tuesday night. That’s where a more easterly component of the surface winds will amplify wind shear, or a change of wind speed and/or direction with height. Greater wind shear bolsters the risk of rotating storms, especially if individual thunderstorm cells remain “discrete” and isolated.

Friday

Toward the midweek, a shortwave trough, or lobe of high altitude cold air, low pressure and spin nestled within a dip in the jet stream, will dive southeast out of the Four Corners region. The chilly bowling ball-like system at the upper levels will trek over the Texas Panhandle before cruising over Oklahoma and Arkansas.

Ahead of it, moisture-rich air will stream north over Mississippi and Alabama, with pockets of it beginning to rise into cold air aloft by Friday afternoon. Thunderstorms will break out during the afternoon or evening and a few could become rotating “supercells.” Each could pose the risk of hail, wind and perhaps a tornado. Southeast Louisiana to southern Georgia, including parts of Mississippi and Alabama along the Interstate 10 corridor, look most at risk.

Early next week

A particularly robust system looks to enter the equation early next week, with the risk of tornadoes across a wide swath of Texas and the South.

A multiday threat could evolve ahead of another shortwave that will linger over West Texas and New Mexico on Monday and Tuesday. That will shunt a “dryline” eastward, or the leading edge of dry, desert air. It will encroach into a soupy air mass, the resulting clash spawning additional severe thunderstorms.

Changing winds with altitude will favor rotating thunderstorms or supercells, meaning tornadoes could develop in some storms.

On Monday, the risk will extend from the Trans-Pecos and Rio Grande Valley to Dallas and East Texas. Cities like San Antonio, Houston, Austin, Waco, Fort Worth and Lufkin will all be at risk.

By Tuesday, it will be a concern for Louisiana, Mississippi and Alabama, and there’s a chance the risk might stretch farther east on Wednesday. Thereafter, the end of March looks active, too.

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