It seems like a long time ago that we last saw thunderstorms here in the Stateline. That is because we have been under the influence of fall. That has led to cooler temperatures, low humidity, and a lack of a thunderstorm threat. That trend continues Friday as scattered showers are expected on the back side of an upper-level low that will be situated in Indiana. However, as the low approaches the Illinois border into Saturday, it will bring a slightly more thunderstorm-friendly air mass into the Rockford region. With the center of the low nearby, some minor instability (CAPE) will develop during the day. That is what thunderstorms need to develop and maintain themselves. Think of CAPE (Convective Available Potential Energy) as food for storms.
For the Stateline, there will be minor CAPE in place Saturday. That, in addition to having the upper-level low so close, will support an environment slightly more conducive to thunderstorms than what we have seen lately. It is not a guarantee by any stretch of the imagination that we see thunder and lightning. But the formula for storms will be more complete than it has of late. The good news is that if we do see a thunderstorm or two, it won't be severe.