The conditions are ripe for a series of storms to gain strength and buffet Middle America over the next two days, with hail and tornadoes possible in parts of the nation's geographic heartland, forecasters warned Wednesday.

Large hail, damaging winds and a number of tornadoes were possible Wednesday from the southern Plains westward to Illinois. The focus shifts to the mid-Mississippi River Valley for Thursday, including Chicago, Indianapolis and St. Louis.

Thunderstorms were already rolling through Indiana and Missouri at dawn, and the Storm Prediction Center said multiple bouts of severe weather would develop through the day. The highest chance of tornadoes Wednesday extended from the Kansas-Oklahoma border south of Wichita, Kansas, to the St. Louis area — with storms forming in the afternoon and early evening.

Another day of warmth Thursday, mixed in with humidity, instability, an approaching front and the jet stream, would contribute to steadily worsening weather.

"By Thursday, it looks like all those ingredients come together. ... You can really blow up some big storms," said Greg Carbin, the warning coordination meteorologist at the Oklahoma-based Storm Prediction Center.

Areas that don't see strong storms Thursday could see heavy rain instead.

The Storm Prediction Center said Wednesday's storms in an area from northern Oklahoma to western Illinois could be significant — defined as having 2-inch hail, 75 mph winds and tornadoes rated at EF2 or higher.

On Thursday, similar storms were forecast for an area from the Arkansas-Missouri border to southern Wisconsin to central Indiana.

The week was already off to a blustery start. Emergency officials said a tornado touched down briefly Tuesday night in southeastern Kansas, and hail and high winds caused problems from St. Louis to southwestern Indiana.