Look at the impressive images of the floods in California 1:38
(CNN Spanish) --
A major multi-hazard storm sweeping across the United States brings with it the danger of strong tornadoes and flooding in the South, and ice and snow across the Plains and upper Midwest on Tuesday.
The storm, which has already caused deadly flooding in California, was expected to drive moisture from the Gulf of Mexico southward, where above-normal temperatures have set the stage for severe thunderstorms.
More than 2 million people were under a tornado watch in parts of Texas, Louisiana, Mississippi, Arkansas and Oklahoma as of Monday night.
Heavy rains also accompany severe storms, creating the threat of flash flooding in northern Louisiana, southeastern Arkansas and northwestern Mississippi, according to the National Weather Service.
In addition to the risk of tornadoes, areas could see scattered hail and powerful wind gusts of up to 70 mph (112 km/h).
More than 12 million people in the South were under a flood watch Tuesday morning, with the heaviest rains expected in parts of southwestern Alabama and southeastern Georgia.
Flood advisories extended from the northern Texas-Louisiana border along the Mississippi River valley to southern Indiana and Illinois.
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tornadoes
Damage has already been reported after a possible tornado in Jessieville, Arkansas, according to Garland County officials.
Officials search debris fields for victims of the tornado on December 14, 2021 in Dawson Springs, Kentucky.
In Jackson Parish, Louisiana, residents were told to stay off the roads as severe weather downed trees and covered roads with water.
The Jackson Parish Sheriff's Department said tarps will be provided to those whose homes have been damaged.
As the risk persists, forecasters have been concerned about tornado formation overnight, according to Brad Bryant of the National Weather Service office in Shreveport, Louisiana.
Anyone in areas at risk for tornadoes should seek safe shelter immediately, Bryant said.
As of 1 a.m., there were 21 storm reports, including one tornado report, 16 wind reports, and four hail reports.
The reported tornado was in Jonesboro, Louisiana where large trees were downed and damaged.
Reports of damage were also coming in from across northern Louisiana, including several damaged high-line transmission towers in the Marion community of Haile.
One of the towers was brought down and several others were damaged, according to the National Weather Service in Shreveport.
An 81 mph (130 km/h) wind gust was reported in Adair, Oklahoma, a gust equivalent to a Category 1 hurricane.
floods
Rain totals in the South through Wednesday are forecast to be 2 to 4 inches with some areas could see up to 6 inches.
A radar-indicated flash flood warning was issued for parts of central Arkansas, including much of Little Rock, through 12:55 a.m. CST.
They have dropped between 2 and 5 centimeters in the area, and it is possible for up to 5 more centimeters to fall.
In response to severe weather and expected flash flooding in parts of Texas, Governor Greg Abbott activated the state's emergency response resources Monday.
Meanwhile, flooded communities in Northern California could be inundated with more rain later this week.
Heavy rains in California affect the situation of workers 4:03
snowfall
As the southern United States braces for flooding and tornadoes, the storm is expected to bring heavy snow, sleet and freezing rain across the Plains and upper Midwest on Tuesday, significantly impacting travel.
Residents in parts of Nebraska, South Dakota, and Minnesota are likely to see heavy snow rates of 2 to 7 inches per hour.
More than 15 million people are under winter weather advisories from Utah to Wisconsin.
Blizzards and snow accumulation Tuesday could result in snow-covered roads and make travel "dangerous, if not impossible," the weather service warned.
Road conditions were already deteriorating Monday night in northwestern Iowa, northern Nebraska and eastern South Dakota, according to the Omaha weather service.
Parts of northern Nebraska have already reported nearly a foot of snow and could get an additional 12 to 18 inches Tuesday, according to the weather service.
About 200 miles of eastbound Interstate 80 in Wyoming, from Evanston to Rawlins, is closed due to continued impacts from 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 interchange in Cheyenne, which covers more than 120 miles.
Significant ice accumulations due to freezing rain, possibly over a quarter of an inch, are expected from northeast Nebraska to northwestern Iowa and southern Minnesota.
Freezing rain will also make conditions difficult for those on foot.
Even a light polish can make sidewalks and driveways slippery.
Accumulations greater than 0.6 cm can cause scattered power outages and break tree limbs, the weather service says.
FloodsWinter StormTornadoes