A strong low pressure system will move out of the northern Plains Wednesday evening and into Iowa and Wisconsin by Thursday afternoon. This will pull the current cold front moving through Wisconsin Wednesday evening, back north as a warm front during the day Thursday. Showers and thunderstorms will develop along the warm front during afternoon, and then ahead of a cold front Thursday evening.
Thunderstorms will come to end once the front passes, which will likely be after 10pm Thursday. Even though the risk for severe weather isn't overly high at the moment, the threat for severe weather is definitely there. Make sure you have a way to receive watches and warnings, and pay attention to the forecast if you're headed out to the Ogle County Fair.