Much colder air arrived Christmas night, causing slush and standing water from the rain and above freezing temperatures on Christmas day to freeze up. The cold air actually came in from the south, curling around the south side of a low pressure system over Wisconsin.
The arrival of the cold air and an upper air disturbance produced an increase in coverage and intensity of lake effect snow showers from Saturday afternoon the 26th through Sunday the 27th. Since the winds were from the south during this time, the heaviest snow totals were limited to counties along the Lake Michigan Shoreline.
The map below is a graphical estimate of the total snowfall from Saturday afternoon through Sunday evening, using radar data and numerous reports from volunteer weather spotters. The National Weather Service would like to thank everyone who submitted reports.