Picturesque 7-hour snow a horror on many area roads

The temperature in Chicago hovered at 0° as the first flakes of snow fluttered to earth around 8:35 a.m. Tuesday morning. Seven hours later, the hardest hit south and west suburban areas had measured up to 7" of snow, while 2.5" accumulated at Midway and 2.1" at O’Hare. Snowfall at such low temperatures is “airy” and brings with it special challenges. Street chemicals, lacking additives to lower the freezing point of the water into which the snow melts, act more slowly. The meltwater produced can freeze in short order, complicating the flow of traffic. (Note: Chicago has added calcium chloride to its street salt since the late 1970s to combat snow accumulations which occur at low temps.) Also, the volume of such snow is often two to three times that of snow which falls at warmer readings. That’s why moisture which in warmer conditions would have produced just an inch or two of snow fluffed into a half a foot to the city’s south. ---By Tom Skilling, WGN-TV Chief Meteorologist