A sprawling line of supercells tore through eastern Arkansas and western Tennessee overnight, killing at least 14 people and reducing parts of two small towns to debris fields, emergency officials said Thursday, as the National Weather Service confirmed at least 31 tornado touchdowns in a single 10-hour stretch.

The hardest-hit communities were Wynne, Arkansas, where a long-track tornado rated preliminarily as EF-4 cut a path more than 38 miles long through residential neighborhoods, and Dyersburg, Tennessee, where a separate twister struck shortly after 1 a.m. local time as families slept. State troopers said search-and-rescue teams were still moving through collapsed homes and a destroyed mobile-home park late Thursday afternoon, and the death toll was expected to rise.

“We have whole blocks where the only thing left standing is the foundation slab and the front steps,” Arkansas Gov. Sarah Huckabee Sanders said in a midday briefing from Wynne, her voice catching at one point. “We are going to need every bit of federal help we can get, and we are going to need it fast.”

President Donald Trump approved an emergency declaration for 14 Arkansas counties and eight Tennessee counties before noon, freeing up Federal Emergency Management Agency assistance for shelter, debris removal and temporary housing. A White House statement said the president would travel to the region “in the coming days.”

The outbreak was the deadliest single-night tornado event in the United States since the December 2021 Quad-State outbreak, according to figures released by the Storm Prediction Center in Norman, Oklahoma. Forecasters had warned for nearly 48 hours that conditions were aligning for a major event, with a rare high-risk outlook issued Wednesday morning across a corridor stretching from northeast Arkansas through western Kentucky.

“All of the classic ingredients lined up — extreme low-level wind shear, a powerful warm sector, and a sharp dry line surging east after dark,” said Dr. Marisa Calderon, a research meteorologist at the National Severe Storms Laboratory. “When supercells fire in that environment after sunset, you get exactly the scenario we fear most: violent, long-track tornadoes hitting populated areas while people are asleep.”

In Wynne, a town of about 8,200 residents some 50 miles west of Memphis, daylight revealed scenes that residents struggled to describe. The local high school’s gymnasium had been peeled open. A church steeple lay across a state highway. At the Cross County Hospital, which lost part of its roof, staff worked through the night under emergency generators to stabilize patients while moving 22 of them to facilities in Jonesboro and Little Rock.

Mayor Jennifer Hobbs said the city had confirmed nine deaths within its limits and counted more than 200 destroyed structures. “We are a small town. Everybody knows everybody,” she said, standing in front of a destroyed pharmacy. “These are our neighbors. These are our kids.”

In Dyersburg, Tennessee Emergency Management Agency Director Patrick Sheehan reported five confirmed deaths and roughly 60 injuries, with at least a dozen people still unaccounted for as of Thursday evening. A Sheehan deputy said the missing figure was expected to drop as cell service was restored and residents reached relatives.

The storm system also produced damaging straight-line winds and softball-sized hail across portions of Missouri, southern Illinois and western Kentucky. A man was killed in Caruthersville, Missouri, when a tree fell on his vehicle. Power outages peaked at just over 410,000 customers across six states, according to PowerOutage.us, with Entergy Arkansas warning that some rural restorations could take a week or longer.

Climate scientists urged caution about attributing any single outbreak to climate change, but several pointed to a now-familiar pattern of severe-weather activity shifting eastward out of the traditional Great Plains “tornado alley” into the more densely populated and heavily forested mid-South.

“What we are seeing, decade over decade, is more frequent significant tornadoes in the Mississippi and Tennessee valleys, and more of them happening at night,” said Dr. Walker Reinhardt, a climate-and-extremes researcher at the University of Oklahoma. “Nighttime tornadoes in this part of the country are roughly twice as deadly as their daytime counterparts. That is a population-exposure problem on top of a meteorological one.”

Insurance industry analysts said early loss estimates were still preliminary but would likely run into the billions. “We are clearly looking at a top-five tornado loss event for the spring season, and the spring season is barely a month old,” said Diane Petrov, a senior catastrophe analyst at Aon. “Reinsurers will be watching what comes next very closely.”

The Red Cross opened nine shelters across the two states and said donations of blood and cash were urgently needed; officials discouraged in-kind donations of clothing and bottled water, citing logistical strain. Volunteer chainsaw crews from as far as east Texas and southern Indiana began arriving in Wynne by Thursday afternoon.

Forecasters at the Storm Prediction Center said a second, smaller round of severe weather was possible Friday evening across Alabama and northern Georgia, though the setup appeared less volatile. A broader Plains pattern in the first week of May was already drawing attention from long-range forecasters.

Sanders, asked whether her state was prepared for what could be a difficult severe-weather season, said the focus for now was on the missing and the displaced. State and federal officials said damage assessments and a fuller casualty count would be released in the coming days.