Updated 600 pm CST Thu Jan 12 2012
Doppler radar produces estimates of snowfall based on a simple relationship between the snowdepth and the amount of melted liquid in the snow, called the Snow to Liquid ratio. This ratio varies from storm to storm and even from hour to hour during a storm, but can give you a pretty good idea of how much snow fell in areas where you do not receive snow reports. Right now our best guess is that the ratio is 15:1, meaning that 15" of snow would have 1" of melted liquid water in it.
The maps below are estimates from about 530 pm CST today. These estimates will be better the farther west you go away from Lake Michigan, where it was relatively warm and there was a good deal of melting snow early in the storm.
The first map shows about how much snow fell in the past hour from roughly 430 pm to 530pm CST. Areas in the dark blue had about 0.5" of snow in the past hour, and the light blue color about 0.75" in the last hour.
The second map shows an estimate of the total snowfall in the past 24 hours ending at the same time. The dark blue shows about 4" or more and the light blue 5" or more.
For comparison, here are the latest available snowfall reports we have received. Keep in mind that some of these reports are a few hours old.
Jeff Craven, Science and Operations Officer
National Weather Service Milwaukee/Sullivan WI