CNN
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A major, multi-hazard storm is barreling across the country on Tuesday and continues to bring the risk of strong tornadoes and flooding to the South, and ice and snow to the Plains and Upper Midwest.

The storm, which triggered deadly floods in California over the weekend, has tracked east and is pulling moisture from the Gulf of Mexico into the South, where above-normal temperatures have set the stage for severe thunderstorms.

More than 35 million people are under some sort of severe weather threat in the South, with the highest risk near the Gulf Coast. Southeast Louisiana and southern Mississippi and Alabama were under a level 3 out of 5 “enhanced” risk of severe weather. Places like Baton Rouge, Montgomery and Gulfport could all see strong storms. A level 2 out of 5 “slight” risk of severe weather covered Nashville, New Orleans and Atlanta.

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Strong tornadoes, large hail and wind gusts topping 70 mph are possible in the most extreme thunderstorms.

“Severe convection with all three modes (tornadoes, hail and damaging winds) is likely,” the National Weather Service office in Mobile warned.

Heavy rainfall is also accompanying the severe storms, creating the threat of flash flooding across the South. Southeastern Alabama and Southwest Georgia are under a level 3 out of 4 “moderate” risk of excessive rainfall. However, portions of Southeast Louisiana, Mississippi, Alabama, Tennessee and Georgia are also under a level 2 out of 4 “slight” risk of excessive rainfall.

Rainfall totals across the South through Wednesday are forecast to be between 2 to 4 inches and some areas could see up to 6 inches.

The system produced dangerous thunderstorms overnight. By 6 a.m., 30 storm reports had been submitted to the National Weather Service, including two tornado reports, 22 high wind reports and six large hail reports. One of the tornadoes that was reported was in Jonesboro, Louisiana, where large trees were knocked downed and damaged. The other was reported in Haywood, Tennessee.

Damage was also reported after a possible tornado in Jessieville, Arkansas, according to Garland County officials.

“Damage was sustained to areas of (a) school due to trees, and power lines. The school was currently in session at the time, however all students have been accounted for and reports of no injury,” the Garland County Sheriff’s Office said in a release.

In Jackson Parish, Louisiana, residents were told to stay off the roads as the severe weather toppled trees and covered roadways with water. Jackson Parish Sheriff’s Department said tarps will be given out to those whose homes are damaged.

“We are trying to work to get to houses that are damaged and clear roads,” the Sheriff’s Department said.

As the risk persists, forecasters have been concerned about tornadoes forming at night, according to Brad Bryant of the National Weather Service office in Shreveport, Louisiana.

“You can’t see them coming. A lot of the time, people are asleep and not paying attention to the weather,” Bryant said. “Many areas around here don’t have good cell phone coverage and storm alerts are not as effective in those areas, especially once people are asleep.”

Anyone in areas at risk of tornadoes should seek safe shelter immediately, Bryant said.

“If you wait around for a warning to be issued, it is too late,” Bryant said Monday. “You need to have a safe shelter plan in place in advance of these storms.”

Damage reports were also coming from across northern Louisiana, including several transmission highline towers being damaged in the Haile community in Marion. One of the towers was knocked over and several others are damaged, according to the National Weather Service in Shreveport.

A wind gust of 81 mph was reported in Adair, Oklahoma – a gust equivalent to a Category 1 hurricane.

Heavy rainfall is also accompanying the severe storms, creating the threat of flash flooding across the South. Southeastern Alabama and Southwest Georgia are under a level 3 out of 4 “moderate” risk of excessive rainfall. However, portions of Southeast Louisiana, Mississippi, Alabama, Tennessee and Georgia are also under a level 2 out of 4 “slight” risk of excessive rainfall.

Rainfall totals across the South through Wednesday are forecast to be between 2 to 4 inches and some areas could see up to 6 inches.

As the South braces for floods and tornadoes, the storm continues to bring heavy snow, sleet and freezing rain across the Plains and Upper Midwest on Tuesday, significantly impacting travel.

Over 15 million people are under winter weather alerts from Colorado to Michigan.

Residents in parts of Nebraska, South Dakota and Minnesota are likely to see intense snow rates of 1 to 3 inches per hour.

Blowing and drifting snow on Tuesday may result in snow-covered roads and make it “hazardous, if not impossible” to travel, the weather service warned.

Road conditions were already deteriorating Monday night in northwestern Iowa, northern Nebraska and eastern South Dakota, according to the weather service in Omaha. Portions of northern Nebraska have already reported nearly a foot of snow and could get an additional 12 to 18 inches on Tuesday, according to the weather service.

Roughly 200 miles of eastbound Interstate 80 in Wyoming, from Evanston to Rawlins, are closed due to the ongoing impacts of the storm, according to the Wyoming Department of Transportation. The department said westbound traffic is further blocked from the Rawlins section of I-80 to the Interstate-25 junction in Cheyenne, which covers more than 120 miles.

“Snow (and) blowing snow to impact Wyoming roads into tonight,” an agency Facebook post read. “A high wind event will then create blowing (and) drifting snow, poor visibility and possible whiteout conditions Tuesday afternoon through Wednesday afternoon for sections of I-80, I-25, South Pass and various secondary roads!”

“If you can, please stay home. If you must travel, ensure you have an emergency kit in your car,” the weather service in Sioux Falls told residents, saying travel will become difficult to impossible by Tuesday morning.

A vehicle winter emergency kit includes snacks and water, a battery-powered weather radio, flashlights and batteries, a first aid kit, a shovel and ice scraper, a jumper cable and other items.

Significant ice accumulations from freezing rain are expected, possibly over a quarter inch, from northeastern Nebraska through northwestern Iowa into southern Minnesota.

The freezing rain poses a significant hazard to those on foot. Even a light glaze can make for slippery sidewalks and driveways. Accumulations more than 0.25 inches can cause scattered power outages and break tree limbs, the weather service says.