Funnel clouds with thunderstorms Thursday evening

John Mershon - Forreston, IL

 Thunderstorms became more numerous over northwest Illinois Thursday evening, producing gusty winds, small hail, torrential downpours and even funnel clouds. The First Warn Weather team received several pictures of funnel clouds from a thunderstorm over northwest Ogle County, and northwest of Forreston, Thursday afternoon. This also prompted the sirens to be activated across Ogle County, although there were no reports of any tornadoes.

It's possible that the funnel cloud that formed northwest of Forreston, IL may have had brief contact with the ground, but then lifted very quickly. These funnel clouds were produced from thunderstorms that were not quite as strong as the thunderstorms that produce tornadoes, known as supercell thunderstorms. However, the funnel clouds were very pronounced!

If the funnel clouds did in fact reach the ground, they would have been called landspouts. A landspout is from a non-supercell thunderstorm and usually has a very narrow, rope-like funnel cloud that forms while the thunderstorm is still growing. This type of thunderstorm has no rotating updraft, like a supercell thunderstorm does, and the spinning typically originates near the surface.

Often times we see this occur when there are smaller scale boundaries - like an old thunderstorm boundary or front. Landspouts look like tornadoes, but form in a different manner than a tornado. They also aren't known to cause a lot of damage like tornadoes. Either way, if you do see a funnel cloud or landspout it's best to seek shelter until the storm has passed. 

Scattered thunderstorms will continue through the remainder of Thursday evening. The overall strong to severe threat has diminished some, however, a few thunderstorms may continue to pose a threat for brief funnel clouds through the 9pm hour before transitioning more to a heavy rain threat through the night. A Flood Watch has been issued for Ogle, Lee and DeKalb counties until 7am Friday for the potential of some localized flooding rain.