article: Forecasters cautioned millions of people in Middle America to keep an eye to the sky Wednesday and Thursday amid threats of hail, high winds and strong tornadoes. The Storm Prediction Center, in a midday update to its forecast Wednesday, upgraded to its second-highest advisory level - a moderate risk - while stressing that a significant tornado or two could form in a narrow stretch from northern Oklahoma to central Missouri. Strong storms swamped Indianapolis, Cincinnati and Charleston, West Virginia, at midday Wednesday and forecasters said more severe weather could form as far away as the plains of West Texas. Scroll down for video . Warning: Some 34 million Midwesterners have been warned of possible powerful tornadoes as a dangerous thunderstorms pummeled the region Wednesday and into Thursday . Not over: A driver in a lifted four wheel drive truck negotiates the deep flood waters on South Shore Drive east of Green Briar Lane after a severe thunderstorm and tornado warning passed through the northeast side of Monroe County, Indiana Wednesday . Indiana State Police said high winds toppled a tractor-trailer on Interstate 69 near Evansville, while utilities reported a number of power outages after wind gusts reached 70 mph. Fewer than 1 million people were in Wednesday's 'moderate risk' area between Wichita, Kansas, and Jefferson City, Missouri, but 34 million were under at least a slight risk of seeing damaging winds, large hail and possibly a tornado. Emergency managers in Kansas and Illinois huddled separately to address the approaching storms. Kansas officials warned that hail could be the size of baseballs, while Illinois officials told residents they should be prepared to seek shelter if bad weather arrives. This car saw the wrong end of a couple of the giant hail stones that fell on Johnson County, Kentucky on Wednesday . Big stones: Hail the size of baseballs battered Missouri, Kentucky and Kansas earlier Wednesday and threatened to do more damage Wednesday night and into Thursday. These fell to Earth in Morgan County, Kentucky around 3pm Central on Wednesday . Rolling through: Strong storms swamped Indianapolis, Cincinnati and Charleston, West Virginia, at midday Wednesday and forecasters said more severe weather could form as far away as the plains of West Texas (map courtesy Weather Channel) Pressure: This NOAA satellite image taken Wednesday showing areas of low pressure systems that is creating areas of severe weather,showers, and thunderstorms. To the south is an area of high pressure, keeping the Southeast clear with calm weather . Heat, humidity and the approach of a cold front and a jet stream could cause severe weather on Thursday, too. Forecasters said 57 million people were at an 'enhanced risk' of seeing storms nearby, including residents in Chicago, Detroit and St. Louis, as well as those in Memphis, Tennessee, and Little Rock, Arkansas. Areas that don't see strong storms Thursday could see heavy rain instead. The Storm Prediction Center said Wednesday's storms in the southern Plains could be significant - defined as having 2-inch hail, 75 mph winds and tornado damage rated at EF2 or higher. Emergency officials said a tornado touched down briefly Tuesday night in southeastern Kansas. Parts of Missouri and Indiana also had severe weather Tuesday. Heat, humidity and the approach of a cold front and a jet stream could cause severe weather on Thursday, too . Forecasters said 57 million people were at an 'enhanced risk' of seeing storms nearby, including residents in Chicago, Detroit and St. Louis, as well as those in Memphis, Tennessee, and Little Rock, Arkansas . h/t Accuweather, Weather Channel .
highlights: Massive hailstones already fell Wednesday during the storm system's first lashings in Missouri, Kentucky and Kansas .
  Strong storms also swamped Indianapolis, Cincinnati and Charleston, West Virginia at midday Wednesday .
  Experts warned that millions were under a moderate tornado threat Wednesday evening into Thursday .
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