Monday will see the greatest risk for severe weather, Van Dam said, as a cold front moves from the West into the Plains.
The threat of severe storms will ease across the Plains on Sunday as numerous storms will move into the Great Lakes and the northeast US. Additionally, damaging winds, large hail and strong tornadoes will be possible across parts of the Southern Plains from Midland, Texas, to Wichita, Kansas.
The National Weather Service issued a tornado watch until 8pm last Saturday for the western half of Arkansas.
On Saturday, waves of severe thunderstorms struck the Southern Plains, bringing tornadoes, large hail and flooding rains.
Meteorologist Jordan Thies in Hastings says the service received more than a dozen credible reports of tornado sightings from around south-central Nebraska, but says some of those were likely of the same tornado.
Over 40 million Americans are under the threat of severe weather today and an additional 13 million are under threat for Sunday, Van Dam said.More news: Trump says ‘Pro-Life’ but favours exceptions for rape, incest
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Storms in this area will be capable of producing isolated tornadoes, wind gusts of up to 70mph, significant hail, flooding downpours and frequent lightning strikes.
Several areas of the country face threats Friday.
The tornado formed and touched down, remaining on the ground for around 15 minutes, according to Flickinger. In Natchez, Mississippi, the Mississippi River has been at flood stage for 133 consecutive days, the National Weather Service tweeted Friday.
Early May, the MS broke its July 9, 1993 record, during the "Great Flood of 1993" when much of it was flooded from Minnesota to the Gulf of Mexico after heavy rainfall, CNN affiliate WQAD reported.
During that time, the flood gauge at Rock Island, Illinois, topped out at 22.63 feet. Its level this month reached 22.64 feet, WQAD said.
Stay tuned to WBZ-TV and CBS Boston.com for updates as warranted through the day. There were reports of a risky and large tornado in Beauregard Parish, Louisiana, early Sunday morning.