A "large and extremely dangerous" tornado that touched down west of Oklahoma City on Friday, causing some damage, was headed toward the city, and a tornado emergency has been declared in the area, the National Weather Service said.
Weather Service meteorologists and storm spotters were tracking the tornado just west of Yukon, a suburb of Oklahoma City, the agency said in a statement. They said it touched down on Interstate 40 and was headed toward Oklahoma City.
Oklahoma television station KFOR reported that the twister had overturned vehicles and done other damage.
The National Weather Service declared a tornado emergency, which is more serious than a warning, for communities west of Oklahoma City including Yukon.
Will Rogers Airport in Oklahoma City has been shut down, and was sheltering 1,200 people, local station KWTV reported.
The Weather Service had earlier issued a tornado watch for parts of Oklahoma, describing weather conditions as "particularly dangerous" a day after more than a dozen reported twisters ripped through the region.
Forecasters said several intense tornadoes were likely, along with storms bringing hailstones of up to 4 inches (10 cm) and damaging wind gusts that could reach 80 miles per hour (129 kph).
"An extremely unstable air mass has developed across much of Central (and) Eastern Oklahoma," the weather service said in an advisory. "This will likely result in rapid development of severe thunderstorms this afternoon and evening."
Forecasters said the winds would pose an increasing threat through the evening and urged residents to watch for severe weather.
"This is a particularly dangerous situation," the advisory said.
Storms in Oklahoma and Arkansas on Thursday left an Arkansas county sheriff dead and at least one man missing in an attempted water rescue, while at least seven other people were injured elsewhere, officials said.
The body of Scott County Sheriff Cody Carpenter was recovered early on Friday, said Keith Stephens, a spokesman for the Arkansas Game and Fish Commission. Authorities continued to search for a missing state game warden after Thursday night's rescue attempt along the Fourche La Fave River.
A man died in Tull, Arkansas, when a tree fell on his car during a possible tornado, said Grant County sheriff's chief deputy, Pete Roberts. A Scott County official said a woman's body was found in floodwaters on Friday.
Arkansas had numerous reports of damage from high winds, heavy rain and possible tornadoes. Entergy Arkansas reported about 15,000 people were without power, down from a peak of about 30,000 customers early on Friday.
Brian Smith, a National Weather Service forecaster in North Little Rock, said damage assessment teams were surveying several counties on Friday after the reports of several tornadoes.
Several storms produced straight-line wind damage and heavy repeated rain, causing flash flooding across Arkansas, he said. Little Rock received more than 3 inches (7.6 cm) of rain in an hour, breaking the hourly record for the state capital, with more thunderstorms and heavy rain possible on Friday, he said. Large, long-lasting thunderstorms known as supercells are responsible for producing the strongest tornadoes, along with large hail and other dangerous winds.
Oklahoma City and Tulsa, as well as Springfield, Missouri, may all be buffeted by Friday's severe weather and possible tornado touchdowns, said Rich Thompson, a lead forecaster at the National Weather Service's Storm Prediction Center in Norman, Oklahoma.
The danger zone included Joplin, Missouri, he added. Joplin was hit by a monster tornado, one of the most catastrophic in U.S. history, that killed 161 people and destroyed about 7,500 homes two years ago.
On Friday, the focus was going to be from southwest Missouri into Oklahoma, Thompson said, referring to the area often referred to as "Tornado Alley."
The twisters on Thursday sent Oklahoma residents scrambling for cover 10 days after a deadly EF-5 tornado struck Moore, Oklahoma, and killed 24 people. The May 20 tornado damaged or destroyed about 13,000 homes in the Oklahoma City suburb.