Large Wind Damage Threat across N. IL and S. WI

Here is a look at the derecho composite parameter:

It appears that the environment has become extremely supportive of cold pool development across this area, which would start a potential squall line capable of widespread wind damage.  Once storms initiate, they will be elevated, which basically means that a storm is not rooted in the boundary layer.  Once they become surface-based, a squall line will develop.  As soon as this happens, and possibly earlier, a severe thunderstorm/possibly tornado watch will be issued.  However, I will not be able to cover this event until after seven o'clock, possibly later.  Stay tuned.