Severe storms could deliver tornadoes, damaging winds and hail from the Gulf Coast to the Midwest from Tuesday afternoon into early Wednesday (local time) - but especially in Southern states including Louisiana and Mississippi, where flooding also is a risk, forecasters say.
More than 40 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.
The largest potential for severe weather, including tornadoes, large hail and strong winds, is for about 1.2 million people from east-central Louisiana to much of Mississippi, including Jackson, the center said. The threat for that area -- a Level 4 of 5, or moderate -- is relatively rare for this time of year, as is the risk for tornadoes, which happen more frequently 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 3.6 million people across parts of Mississippi and Louisiana as well as a small part of eastern Texas, eastern Arkansas, southwestern Tennessee and western Alabama.
"Multiple rounds of severe thunderstorms -- some capable of long-tracked tornadoes with EF3+ damage potential will be possible this afternoon into tonight over parts of the lower Mississippi Valley region and Mid-South," the center said, referring to a scale of EF0 to the strongest EF5.
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 has 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.
Storms could cause flooding, especially in the South
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.
In anticipation of the storms, the Mississippi Emergency Management Agency urged residents to document property that could get damaged.
"We encourage Mississippians to take photos of their home BEFORE the storms. These photos can be used for insurance purposes and/or possible assistance if your home is damaged in the storm," the agency said on its Twitter account.
This is the first time since the Storm Prediction Center started using its five-tier risk system in 2014 that a Level 4 risk of severe storms has been announced twice in November, CNN meteorologist Taylor Ward said.
The other Level 4 came on the fourth day of this month, when 62 tornado reports were made across Texas, Oklahoma, Arkansas and Louisiana, according to the prediction center. Many homes and businesses were damaged.
CNN
