Showers and thunderstorms are on the increase Wednesday evening ahead of an advancing warm front and low pressure system.
As of 7pm a line of heavy rain and thunderstorms extend from near Brodhead, WI all the way down to Dixon. Very heavy downpours will occur with this line as it advances north and northeast. Thunderstorms this evening are forming north of a strong a warm front and are moving through an environment with little instability. However, wind shear in the atmosphere over northern Illinois is very high. Wind shear is the changing of wind speed/direction with height.
While our overall severe threat remains low the high wind shear environment could cause some of these storms to rotate producing brief funnels as they move through. Very rarely do these types of funnels reach the ground. The biggest concern as these storms pass will be the heavy rainfall.
This line will pass through by 10pm with scattered showers and thunderstorms expected into Thursday morning.