Constance Lambert embraces her dog after finding it alive when returning to her destroyed home in Tupelo, Miss., Monday, April 28, 2014. Lambert was at an event away from her home when the tornado struck and rushed back to check on her pets. (Photo by Brad Vest/AP Photo/The Commercial Appeal)

People walk between two destroyed houses in Mayflower, Arkansas on Monday. (Photo by Danny Johnston/Associated Press)

Jodi Walls pushes a box of belongings out of a friends house while cleaning up after a large tornado made its way along Clayton Ave in Tupelo, Miss., Monday, April 28, 2014. (Photo by Brad Vest/AP Photo/The Commercial Appeal)

Sunday night, Lauren Watts searches for her dog in Mayflower, Arkansas., after a tornado struck the town. (Photo by Benjamin Krain/The Arkansas Democrat-Gazette)

Residents survey damage along a street in Tupelo, Mississippi on Monday. (Photo by Thomas Graning/The Daily Mississippian)

A concrete slab and rubble are all that is left of a home in a Vilonia, Arkansas neighborhood. (Photo by Danny Johnston/Associated Press)

Nicholas Lee surveys the damage at his parents home off Cemetery Street in Vilonia, Arkansas on Monday. (Photo by Karen E. Segrave/Associated Press)

John Smith reacts after seeing what's left of his auto repair shop in Mayflower, Arkansas on Monday. (Photo by Karen E. Segrave/Associated Press)

A row of lightly damages houses, top, face destroyed homes in a Vilonia, Ark., neighborhood Monday, April 28, 2014 after a tornado struck the town late Sunday, killing at least 16 people. (Photo by Danny Johnston/AP Photo)

John Ward, an automobile and RV dealer, looks at tornado damage to one of his trucks in Mayflower, Ark., Sunday, April 27, 2014. At least 16 people died Sunday night in Arkansas as a tornado carved an 80-mile path of destruction. (Photo by Danny Johnston/AP Photo)

This Friday, April 15, 2011, file photo, shows an SUV that has come to rest on a tree in Tushka, Okla. A large section of the Midwest and South are at risk for strong tornadoes, severe thunderstorms and flash flooding this weekend, forecasters say. (Photo by Sue Ogrocki/AP Photo)

People search through the rubble of destroyed houses a day after a tornado hit the town of Vilonia, Arkansas April 28, 2014. (Photo by Angie Davis/Reuters)

Piles of mangles cars and destroyed homes sit along Aspen Creek Drive in the Parkwood Neighborhood off Naylor Road in Vilonia, Ark., Monday, April 28, 2014 after a tornado struck the town late Sunday. (Photo by Karen E. Segrave/AP Photo)

People sift through the rubble of what is left of homes after a tornado hit the town of Vilonia, Arkansas April 28, 2014. Workers searched for survivors on Monday in the rubble left by a wave of tornadoes that ripped through the south-central United States a day earlier, killing at least 18 people in Arkansas, Oklahoma and Iowa. (Photo by Carlo Allegri/Reuters)

Piles of cars and remnants of homes sit along Highway 64 in Vilonia, Ark., Monday, April 28, 2014, after a tornado struck the town late Monday. Vilonia was hit hard Sunday after a tornado system ripped through several states in the central U.S. and left more than a dozen dead in a violent start to this year's storm season, officials said. (Photo by Karen E. Segrave/AP Photo)

Justin Shaw, left, helps Nick Conway erect a flag pole at his home that was destroyed by a tornado, Monday, April 28, 2014, in Vilonia, Ark. (Photo by Eric Gay/AP Photo)

Travel trailers and motor homes are piled on top of each other at Mayflower RV in Mayflower, Ark., Sunday, April 27, 2014.A powerful storm system rumbled through the central and southern United States on Sunday, spawning tornadoes. (Photo by Danny Johnston/AP Photo)

Twisted trees and power lines remain in a residential block near Military Avenue following the tornado in Baxter Springs, Kan., Sunday, April 27, 2014. A powerful storm system rumbled through the central and southern United States on Sunday, spawning a massive tornado that carved through Little Rock's northern suburbs and another that hit Oklahoma and Kansas. (Photo by Roger Nomer/AP Photo/The Joplin Globe)

A man tries to salvage belongings from a overturned mobile home in Greenville, N.C. on Saturday, April 26, 2014 after a tornado touched down along Black Jack Simpson Road on Friday. Officials said multiple tornadoes damaged more than 200 homes the previous day and sent more than a dozen people to the emergency room. (Photo by Aileen Devlin/AP Photo/The Daily Reflector)

First responders, volunteers and firemen gather on Main Street in Quapaw after a tornado struck the city. (Photo by Gary Crow/AP Photo/Tulsa World)

A man goes throws a pile of clothing Saturday, April 26, 2014, from the debris after a tornado touched down along Black Jack-Simpson Road on Friday, April 25, 2014. (Photo by Aileen Devlin/AP Photo/The Daily Reflector)

A officer talks to people at 15th and Military following tornado in Baxter Springs. (Photo by Roger Nomer/AP Photo/The Joplin Globe)

A damaged vehicle is seen after a tornado hit the town of Mayflower. (Photo by Gene Blevins/Reuters)