* WHAT. Flash flooding caused by thunderstorms producing excessive rainfall is possible. * WHERE. A portion of north central Illinois, including the following counties, Boone, Lee, Ogle and Winnebago. * WHEN. From 2 PM CDT this afternoon through this evening. * IMPACTS. Creeks and streams may rise out of their banks. Flooding may occur in poor drainage and urban areas. Roads and streets may be flooded. * ADDITIONAL DETAILS. - Additional showers and thunderstorms are expected later this afternoon into this evening. The stronger storms will be capable of producing rainfall rates in excess of 2 inches per hour. If storms persist over a given area for a couple of hours, then those isolated locations could see rainfall totals in excess of 4 inches this afternoon and evening. Rainfall of this magnitude would likely result in flash flooding, particularly if it occurs in areas that saw heavy rainfall and flooding Thursday. - http://www.weather.gov/safety/flood