Widely isolated showers developed Tuesday afternoon and evening and produced brief heavy downpours. Lightning was absent from most of the shower activity, so thunder was extremely limited.
The showers developed as an upper level low moved over southern Wisconsin and northern Illinois. At the surface, there was a weak boundary (wind convergence line) over northern Illinois. Cumulus clouds started to build high in the sky as the low passed overhead. The quickly rising clouds and boundary near the surface allowed enough convergence and spin to develop in the atmosphere to produce brief funnel clouds.
The pictures above were taken shortly after 12:30pm Tuesday afternoon from Browns Mill Road in Stephenson County, looking to the east/southeast. The photos are from Patrick Murray. You’ll notice the funnel isn’t very big and is not attached to a thunderstorm cloud. These types of funnel clouds rarely touch down and typically don’t last too long. If they do touch down, minimal damage can occur.