Deadly Midwest Tornadoes: At Least 18 Killed in 3 States

MAYFLOWER, Arkansas (CNN) -- Parts of the South and Midwest could be in for more severe weather Monday, a day after suspected tornadoes killed at least 18 people in three states, including 10 who died in one devastated Arkansas county."It's chaos here," said James Firestone, mayor of Vilonia, Arkansas, one of the two hard-hit towns in Faulkner County. "Our downtown area seems like it's completely leveled.""There's a few buildings partially standing, but the amount of damage is tremendous," he said Sunday. "There's gas lines spewing. Of course, power lines down. Houses are just a pile of brick."Widespread damage was also reported in the nearby Arkansas town of Mayflower."There were cars flipped everywhere, there were people screaming," James Bryant, a Mississippi State University meteorology student who witnessed the storm, told CNN's "New Day" on Monday. "It was a tough scene."As rescue crews continued to search for anyone who may remain trapped and residents began the long job of cleaning up, forecasters warned of more potentially dangerous weather Monday. About 3 million people were under a moderate threat of severe weather Monday, CNN meteorologist Indra Petersons said. About 24 million were at slight risk of severe storms, she said.Monday's forecast calls for a moderate risk of severe thunderstorms, tornadoes and hail in parts of the South. Portions of Mississippi, Alabama, Tennessee and Louisiana are at the greatest risk, according to the Storm Prediction Center.The storms also will stretch into the Midwest and Ohio River Valley, with much of Illinois, Indiana and Kentucky at a slight risk of severe weather, according to forecasters.'A huge black cloud'In Sunday's storms, at least 16 people died across Arkansas. In addition to the Faulkner County deaths, the Arkansas Department of Emergency Management said five people died in Pulaski County and one died in White County. Authorities reported one storm-related death in Oklahoma and another in Iowa.The storms boiled up after nearly a week of forecasts calling for severe weather, including a rare "high risk" warning from the National Weather Service's Storm Prediction Center.Resident Bryant Pruitt said he ducked into his house when he saw a storm cloud approaching from the southwest."It was huge. It was by far the biggest one I've ever seen," he told CNN affiliate KTHV. "It was a huge black cloud ... and I ran inside."It was much the same in Mayflower, a town of 1,600 about 20 miles to the southwest.Authorities shut down a section of Interstate 40 after a tornado "as much as a half-mile wide" roared through the area, according to the National Weather Service. The heavily used road was littered with crushed and overturned trucks and cars.CNN meteorologist Chad Myers, who was in Mayflower, estimated the winds from the storm were at 130 to 150 mph.Emergency workers tended to the scene throughout the night. Shelters were set up at the high school and at a local church.The city's official website said schools would be closed Monday.In Vilonia, a community of about 3,800 people, the nightmare of a tornado strike is all too familiar. Another storm ransacked the town almost three years ago to the day and followed essentially the same path, the mayor said.National Weather Service meteorologist Jeff Hood said that at least one long-track tornado began in Pulaski County northwest of Little Rock and moved northeast from there. The office will survey the damage in the coming days to determine the rating of the tornado and if any other tornadoes hit in the region, he said.President Barack Obama offered his condolences to storm victims while on a four-nation tour of Asia."I want all affected to know FEMA is on the ground and will help Americans in need, and your country will be there to help and rebuild as long as it takes," he said from the Philippines.'Tell the public to stay away'Before the bad weather slammed into Arkansas, witnesses spotted a twister in the northeast Oklahoma town of Quapaw, where one person died, the Ottawa County Sheriff's Office said.Joe Dan Morgan, the county's emergency manager, said rescuers were working in an area where a concrete wall crashed onto a car.There were other reports of damage in the community, stretching thin local resources."Search and rescue is under way involving several agencies," county emergency dispatcher Kelly Flecks said. "Please tell the public to stay away so they can do their jobs. We can't confirm anything else at the moment."Quapaw is near the border with Kansas and Missouri.The same line of storms hit Baxter Springs, Kansas, just a few miles to the north.Sixty to 70 homes and at least 20 businesses were reported destroyed, said Cherokee County emergency manager Jason Allison. A tornado estimated to be three blocks wide rumbled through the town of 4,200, he said. A sprawling storm front also hit eastern Iowa, killing a woman in the tiny community of Kinross in Keokuk County, the sheriff's department said.The one bright spot amid Sunday's devastation were the forecasts that predicted the severe weather days ago, said storm chaser Brett Adair.The advance notice helped save lives, said Adair, whose team witnessed the Faulkner County storm, then helped victims."This definitely was not something to take lightly," he said.------------------------------------------------------------------------------- (CNN) -- Here's a look at what you need to know about tornadoes, which are funnel-shaped clouds that form under thunderclouds and contain rapidly rotating air.Facts: Most tornadoes form from severe thunderstorms. Hurricanes can also produce tornadoes.Tornado winds may exceed 300 miles (480 kilometers) per hour.Tornadoes can lift cars, mobile homes, and animals into the air.Tornadoes are sometimes called "twisters."The damage path of a tornado is usually less than 1,600 feet wide.Most tornadoes move at less than 35 miles per hour.Most tornadoes last only a few minutes.The most destructive and deadly tornadoes occur from supercells, which are rotating thunderstorms with a well-defined radar circulation called a mesocyclone. Supercells can also produce damaging hail, severe non-tornadic winds, unusually frequent lightning, and flash floods.A tornado over a body of water is called a "waterspout."The United States has the highest number of tornado occurrences in the world with an average of 1,000 tornadoes reported each year. According to the National Weather Service, in 2013 there were 55 tornado-related deaths in the United States. Most of the tornadoes in the United States strike in Tornado Alley, which spans the Midwest and the South. Tornadoes usually occur during the spring and early summer, most often in the late afternoon and early evening.A tornado watch is issued by the National Weather Service when atmospheric conditions promote the forming of tornadoes.A tornado warning is issued when Doppler radar detects a mesocyclone in a thunderstorm, or when a funnel cloud has been spotted. A tornado emergency is enhanced wording in a tornado warning indicating a large tornado is moving into a heavily populated area. Significant widespread damage and numerous fatalities are likely. The term was coined by forecasters in May 1999 and is used sparingly. Enhanced Fujita Scale: The Fujita scale is used to estimate the wind speed of a tornado by the damage the tornado causes. EF0 is the weakest point on the Enhanced Fujita Scale and EF5 is the strongest.An EF5 tornado can tear a house off its foundation.Category EF1 Wind speed: between 86 and 110 miles per hour. Moderate damage. Peels surface off roofs; mobile homes pushed off foundations or overturned; moving autos blown off roads. Category EF2 Wind speed: between 111 and 135 miles per hour. Considerable damage. Roofs torn off frame houses; mobile homes demolished; boxcars overturned; large trees snapped or uprooted; light-object missiles generated; cars lifted off ground. Category EF3 Wind speed: between 136 and 165 miles per hour: Severe damage. Roofs and some walls torn off well-constructed houses; trains overturned; most trees in forest uprooted; heavy cars lifted off the ground and thrown. Category EF4 Wind speed: between 166 and 200 miles per hours. Devastating damage. Well-constructed houses leveled; structures with weak foundations blown away some distance; cars thrown and large missiles generated. Category EF5 Wind speed: 200 plus miles per hour. Incredible damage. Strong frame houses leveled off foundations and swept away; automobile-sized missiles fly through the air in excess of 100 meters (109 yards); trees debarked; incredible phenomena will occur.Timeline: March 18, 1925 - One of the worst tornado disasters in the United States. 695 people in the tri-state area of Missouri-Illinois-Indiana are killed. It is the longest-lived and has the longest path of any recorded U.S. tornado.1950 - The U.S. begins keeping official records about tornadoes. April 3-10, 1974 - There are 148 tornadoes in 16 states.May 12-18, 1995 - There are 173 tornadoes in 18 states.May 5-10, 2003 - There are 395 tornadoes reported in 19 states.February 2, 2007 - At least 20 people are killed in Lake and Volusia counties in Florida after at least three tornadoes touch down in the middle of the night.March 1, 2007 - At least 20 people are killed, one in Missouri, 10 in Alabama, and nine in Georgia from a string of tornadoes. In Alabama, eight of the 10 killed are teenagers from Enterprise High School in Enterprise, Alabama. February 5, 2008 - At least 56 people are killed, 32 in Tennessee, 13 in Arkansas, seven in Kentucky, and four in Alabama from a string of tornadoes.March 14, 2008 - A tornado reaching EF-2 strength at times hits downtown Atlanta, Georgia, damaging the World Congress Center, CNN Center, the Georgia Dome, Cotton Mill Lofts, and many other buildings. May 9-11, 2008 - A series of tornadoes kills 22 in three states including six in Ottawa County, Oklahoma; 13 in Newton County, Missouri; one in Jasper County, Missouri; one in an area of Purdy in Barry County, Missouri, and one in Laurens County, Georgia.April 14-16, 2011 - At least 114 tornadoes touch down in Oklahoma, Kansas, Louisiana, Mississippi, Alabama, Missouri, Illinois, Georgia, South Carolina, North Carolina, Virginia, Maryland, Arkansas and Pennsylvania. Of the 46 fatalities reported, 23 occur in North Carolina. April 25-28, 2011 - An outbreak of 201 confirmed tornadoes occurs from 8:00am ET April 25 to 8:00am ET April 28, 2011. There are approximately 321 fatalities in six states during the entire outbreak from April 25 to April 28. The majority of fatalities occur in Alabama, where as many as 243 people perish. Other states reporting fatalities are Mississippi, Tennessee, Georgia, Virginia and Arkansas. In terms of multi-day outbreaks, this outbreak holds the record for the largest number of tornadoes.May 22, 2011 - An E5 tornado strikes Joplin, Missouri, killing at least 158 people. It is the deadliest single U.S. tornado since federal record-keeping began in 1950. The tri-state tornado of 1925 is still the deadliest tornado in U.S. history. May 24, 2011 - Tornadoes strike Arkansas, Oklahoma and Kansas, killing at least 18 people.August 3, 2011 - The Storm Prediction Center's final report for April 2011 shows 753 tornadoes touched down across the U.S., breaking the previous monthly record of 543 tornadoes in May 2003.March 2-3, 2012 - At least 42 tornadoes sweep across 10 states, killing 39 people. Of the 39 fatalities reported, 21 occur in Kentucky, 13 in Indiana, three in Ohio, one in Alabama and one in Georgia.May 20, 2013 - An EF5 tornado hits the Moore, Oklahoma area. The path of the tornado is 14 miles long. Twenty-four people are killed. Top Ten Deadliest Single U.S. Tornadoes: March 18, 1925 - Tri-state area of Missouri, Illinois and Indiana - 695 fatalities. May 6, 1840 - Natchez, Mississippi - 317 fatalities. May 27, 1896 - St. Louis, Missouri - 255 fatalities.April 5, 1936 - Tupelo, Mississippi - 216 fatalities.April 6, 1936 - Gainesville, Georgia - 203 fatalities. April 9, 1947 - Woodward, Oklahoma - 181 fatalities.May 22, 2011 - Joplin, Missouri - 158 fatalities.April 24, 1908 - Amite, Louisiana and Purvis, Mississippi - 143 fatalities. June 12, 1899 - New Richmond, Wisconsin - 117 fatalities. June 8, 1953 - Flint, Michigan - 116 fatalities. Top Ten Costliest Tornadoes since 1950: (in 2013 dollars) May 22, 2011 - Joplin, Missouri - $2.8 billion (actual cost) - $2.9 billion (adjusted for inflation)April 27, 2011 - Tuscaloosa, Alabama - $2.45 billion (actual cost) - $2.5 billion (adjusted for inflation)June 8, 1966 - Topeka, Kansas - $250 million (actual cost) - $1.79 billion (adjusted for inflation)May 11, 1970 - Lubbock, Texas - $250 million (actual cost) - $1.5 billion (adjusted for inflation)May 3, 1999 - Oklahoma City, Oklahoma - $1 billion (actual cost) - $1.4 billion (adjusted for inflation)April 27, 2011 - Hackleburg, Alabama - $1.2 billion (actual cost) - $1.33 billion (adjusted for inflation)April 3, 1974 - Xenia, Ohio - $250 million (actual cost) - $1.18 billion (adjusted for inflation)May 6, 1975 - Omaha, Nebraska - $250 million (actual cost) - $1.08 billion (adjusted for inflation)April 10, 1979 - Wichita Falls, Texas - $277 million (actual cost) - $893 million (adjusted for inflation)June 3, 1980 - Grand Island, Nebraska - $285 million (actual cost) - $807 million (adjusted for inflation)