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CNN —
Numerous tornadoes – including a few intense ones – are possible Tuesday afternoon and evening for parts of Arkansas, Louisiana and Mississippi as severe storms rake the area, a situation that moved forecasters to issue a special tornado watch alerting residents to an unusual level of risk.
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A “particularly dangerous situation” tornado watch, reserved for the most significant severe-storm threats and used in only 3% of watches, was issued for some areas in those states by the Storm Prediction Center.
The watch, covering nearly 2.5 million people in far southeastern Arkansas, northern and central Louisiana and central Mississippi, was set to be in effect from shortly after noon to 7 p.m. CT.
This comes as severe storms could hit a much wider area of the United States from Tuesday into early Wednesday, from the Gulf Coast to the Midwest, with tornadoes, damaging winds and hail, forecasters said.
But prediction center forecasters focused especially on Arkansas, Louisiana and Mississippi, saying “parameters appear favorable for strong and long-tracked tornadoes,” meaning ones that stay on the ground for an extended period, Tuesday afternoon and early evening in the watch area.
“Numerous tornadoes (are) expected with a few intense tornadoes likely,” along with scattered large hail and scattered damaging wind gusts up to 70 mph, forecasters said in the special tornado watch.
Overall, more than 41 million people from southeastern Texas eastward to Georgia and northward to central Indiana and Illinois are under at least a marginal threat of severe weather Tuesday, according to the Storm Prediction Center.
Separate from the special tornado watch, the prediction center laid out an area where it believed the largest potential for severe weather, including tornadoes, existed – covering 1.6 million people in east-central Louisiana; a sliver of southeastern Arkansas; much of Mississippi, including Jackson; and northwestern Alabama. The threat for that area – a Level 4 of 5, or moderate – is relatively rare for this time of year, and tornadoes, though they can happen year-round, are more frequent in the spring and summer.
“Severe thunderstorms in the fall and winter can be extremely impactful and may sometimes catch people off guard as thunderstorms tend to occur less frequently during the cooler months,” Bill Bunting, chief of forecast operations at the Storm Prediction Center, told CNN Weather.
A Level 3 of 5, or enhanced, risk zone encircles that area, covering 2.8 million people across parts of Mississippi and Louisiana as well as a small part of eastern Texas, southeastern Arkansas, southwestern Tennessee and western Alabama.
What is a long-track tornado?
Some tornadoes could happen overnight Tuesday into Wednesday, making them even more threatening because it’s harder during those hours to alert people to take shelter.
“Another challenge with nighttime tornadoes, especially in the fall and winter, is that storms typically move very quickly, at times 50 or 60 mph,” Bunting said.
“This means that you must make decisions quickly and take shelter based on information contained in the severe thunderstorm or tornado warning, and not wait until the storm arrives,” Bunting added.
The same storm system also brought heavy snowfall to 13 states across the West and Upper Midwest, where millions of people were under winter weather advisories and winter storm warnings Tuesday morning.
Generally about 2 to 4 inches of rain could fall in the south-central United States, and the total could be greater in far southern parts of Mississippi and Alabama, where the storms could stall, the Weather Prediction Center said.
That could cause flooding in those areas, where the soil is damp from recent rains, the prediction center said. Flood watches are in place Tuesday in parts of southeastern Louisiana and southern Mississippi and Alabama.