Severe thunderstorms will tear through a part of the nation's midsectionovernight. The squeeze between southern Plains heat and central Plains coolwill spark powerful thunderstorms over the northern two-thirds of Illinois andMissouri as well as southern Iowa, southeastern Nebraska and eastern Kansas.Major cities at risk will include Kansas City and St. Louis. The severeweather threat could also extend to Chicago as well as Omaha.

Bursts of wind above 60 mph could cause damage in stronger thunderstorms. Afew will even spew large hail an inch or more in diameter. Flooding downpourswill be possible, too.

There will be eastward expansion of the at-risk area on Tuesday as theatmospheric setup favorable for severe thunderstorms persists.

Story by AccuWeather.com Meteorologists Jim Andrews