Nightime cooling of the atmosphere within a thousand feet of the ground often occurs in Wisconsin, resulting in formation of a low-level inversion. Below the temperature inversion fog can develop if the air cools down ot its dew-point value. Additionally, the inversion acts as a lid and traps any smoke or pollution.
Just after sunrise on the morning of June 11, 2013, fog and smoke was trapped below a low-level temperature inversion in the Wales area of Waukesha County. Mark Was, photographer at WTMJ-4 Milwaukee, took a picture of the trapped fog and smoke. Note how the ridge tops poke above the trapped fog and smoke. The smoke was likely related to a fire and was drfting into the picture from the mid-point of the left side of the picture. Click on image for larger version.