The National Weather Service has issued repeated advisories warning that several rounds of thunderstorms will sweep across northern Illinois and northwest Indiana from late Monday night into Tuesday evening. Forecasters say the best-organized storms are expected along and southeast of Interstate 55, with additional activity possible near the I-80 corridor. Any of the storms may generate frequent lightning, pea-size hail, torrential downpours and isolated wind gusts reaching 50–60 mph. Rainfall totals of roughly 0.5 to 1 inch are anticipated for much of the Chicago metropolitan area, with locally higher amounts where cells stall, raising the risk of brief flash flooding. A fast-moving line of storms capable of 40-mph gusts was already moving through southern Wisconsin early Tuesday, and meteorologists expect new development over northern Illinois by afternoon. Residents are advised to monitor updated warnings, move indoors when thunder roars and use caution on water-logged roads.