A cut-off low pressure system spinning to the south will continue to feed moisture north into Illinois and Wisconsin Wednesday evening, keeping the chance for isolated thunderstorms through Thursday morning. The biggest impact of any storm during the overnight will continue to be heavy rainfall.
Isolated showers will be possible Thursday morning, but storm coverage is expected to increase during the late morning and afternoon. Low pressure to the south will provide moisture into the Stateline as a cold front moves in from the northwest. Weak winds in the atmosphere won’t do much to push storms along during the afternoon, increasing the risk for heavy rainfall to occur as storms move over the same areas from the southwest to the northeast.
Rainfall amounts over one inch will be possible Thursday, especially over southern Wisconsin and far northern Illinois. The risk for widespread flash flooding is low, but rainfall amounts over one inch could increase flash flooding locally. Soil moisture is back within the 95th percentile over northern Illinois and southern Wisconsin, so any additional heavy rain that comes down could cause some flooding concerns. The cold front is expected to pass through Thursday evening with drier conditions expected during the overnight, and into Friday.