Atmospheric conditions, along with a favorable wind direction, has resulted in the area wind farms showing up clearly on the radar display overnight (see image below.) Given the low level inversion that was in place, and the superrefraction of the radar beam that was likely occurring, the radar energy was intercepting the large blades of the wind turbines. See this related web page about how our radar "sees" these wind farms. The returned energy is plotted on the display and looks just like precipitation, or even thunderstorms. Also, due to the easterly flow, the motion of the wind turbine blades is generally parallel to the radar beam, maximizing the radars ability to interpret their motion. The radar has the ability to remove "targets" that aren't moving (something we call clutter suppression.) This is why you generally won't see the interference from the terrain surrounding the radar. But, the wind turbines are moving and therefore the radar assumes they are real precipitation targets.
In the image above, the red circles highlight the wind farm locations. The light green diamond area over Ozaukee county is a shower with no wind farm interference. The one wind farm over Columbia county has a shower moving through it. This is easily determined by looping a few images of the radar display. The wind farms were stationary, while any showers were moving to the north at around 15 mph.