Multiple rounds of organized thunderstorm activity is expected through the next 7 days as a series of upper-level disturbances track from the Plains into the Midwest. The first round of storms is expected across a familiar corridor of the Great Lakes and Ohio Valley, or from Iowa across portions of Wisconsin, Illinois, Indiana, Ohio, and southern lower Michigan.
Tonight (Monday): Storms are expected to develop after sunset across Iowa as warm, moist air lifts north into the region and interacts with a boundary draped across the area. The atmosphere will be supportive of strong, organized storms, including a few supercells early on.
The main concern with these storms will be large hail, potentially impacting northern Illinois and southern Wisconsin as storms move east this evening. As we lose daytime heating, storms should gradually weaken, but they are expected to continue overnight into Michigan with a lower-end risk of hail and gusty winds.
Here's a model simulated look at how storms could evolve early Monday PM:
Tuesday: Some leftover showers and storms may be ongoing Tuesday morning, but there is potential for the atmosphere to recover by afternoon as the next system approaches.
New thunderstorms are expected to develop by early to mid-afternoon from the Upper Mississippi Valley into areas near Lake Michigan. Early in the development phase, storms may remain somewhat isolated, which could again support a large hail threat.
As the day goes on, storms are expected to organize into clusters or lines along an approaching cold front. This will shift the primary threat toward damaging winds, especially across Michigan and into the Lake Erie region.
There is also a risk for a few tornadoes Tuesday evening, particularly across parts of the lower Great Lakes. This will depend on whether storms can stay somewhat discrete ahead of the main line, but the environment will be supportive of rotation if that occurs.