A storm brewing in the Pacific Ocean has forecasters warning of possible severe weather, including tornadoes, in the nation's midsection Wednesday, with Missouri and Arkansas the most likely targets.

The National Weather Service's Storm Prediction Center in Norman, Oklahoma, said Sunday the fast-moving storm is expected to collide with moisture and humidity rising from the Gulf of Mexico, creating unstable weather conditions that could lead to tornadoes as strong as EF3, which include winds of 136 to 165 mph capable of severe damage.

"It's a pretty potent system," Storm Prediction Center meteorologist John Hart said.

Hart said Sunday it is difficult to predict with precision exactly where the systems might meet.

"If the system slows down, it would be in the Oklahoma, Texas, Kansas area. Then, if it sped up, it might be all east of the Mississippi (River) on Wednesday," Hart said. "But everything right now is pointing to that Tennessee, Arkansas, Missouri and Kentucky area."

An SPC map Sunday showed the most threatened areas include most of Arkansas and Missouri and portions of Southern Illinois, western Kentucky, western Tennessee and northwestern Mississippi.

Cities in the most threatened area include Little Rock, Arkansas; St. Louis; Memphis, Tennessee; Jackson, Tennessee; and St. Charles, Missouri.

Among the cities the map shows facing a lesser threat are Dallas, Oklahoma City, Kansas City, Indianapolis and Nashville, Tennessee.

Strong tornadoes in mid-November are not common but not unheard of, Hart said.

"People in that area should be paying attention," he said.