10pm UPDATE: Isolated thunderstorms continue to move across north-central Illinois Tuesday evening, producing very heavy rainfall and frequent lightning for some.
Widely isolated showers and thunderstorms have developed Tuesday evening, sandwiched between an area of low pressure to the southwest and high pressure to the northeast. Any storms that do develop during the evening will have the potential for locally heavy rainfall, but the risk for flooding remains extremely low. Some of the stronger storms could also have a few stronger wind gusts.
The showers and isolated storms will last through sunset with partly cloudy skies expected during the overnight. An area of low pressure, known as an MCV (mesoscale convective vortex) currently sits in west-central Illinois and has been responsible for heavy rain and thunderstorms across central Illinois for much of Tuesday. As that low slowly lifts north Tuesday night, it will run into a little more dry air due to high pressure focused over the Great Lakes. That high will begin to sink a little further to the southwest, closer to northern Illinois and southern Wisconsin Wednesday morning and afternoon. As a result, it’ll focus the higher rain and storm chances across northwest Illinois during the day Wednesday. Temperatures near 70 degrees overnight Tuesday will once again warm into the upper 80s, to near 90 degrees Wednesday.