The combination of a developing upper level low pressure system and lake enhanced snowfall produced significant snowfall across southern Wisconsin on Thursday. Snow overspread southern Wisconsin overnight Wednesday night into early Thursday depositing between 1 and 4 inches across much of the area. The snow continued to fall throughout the day and increased in intensity in the afternoon. At the same time, increasing north to northeast winds in the low levels of the atmosphere and an unstable atmosphere over Lake Michigan produced bands of heavy lake effect snowfall, which began to affect southeast Wisconsin from late afternoon through the evening.
The heaviest band of lake enhanced snowfall affected portions of Sheboygan, Washington, Ozaukee, Milwaukee, Waukesha, Racine, Kenosha and Walworth counties between 8 pm and midnight. This lake enhanced band deposited 2 to 4 inches of snowfall in a period of 1 to 2 hours.
As you can see from the below map which illustrates the estimated snowfall from Thursday, this lake enhanced band of snowfall caused some locations to reach double digit snowfall in this area. The highest reports were about a foot in Jackson, as well as in southeast Racine and Kenosha counties.
For the latest map of how much snow has fallen, check out the following links:
Outside our office we have three acoustic snow sensors that measure snow depth on the ground. These sensors are not official measurements, but they are good with showing trends, and pointing out some interesting features. In the graph below, you can clearly see where the heavy burst of snow occurred late in the evening on the 7th. Sensor 1 was likely affected by some drifting at this time. You can also see how much blowing and settling can affect snow depth in a rather short period of time. The light green line is an average of the readings from each of the three sensors.