|RED: 1000-700mb = 2840m CYAN: 850-700mb = 1540m YELLOW: 1000-850mb = 1300m PURPLE: 700-500mb = 2560m||GREEN: 850-500mb = 4100m WHITE: 1000-500mb = 5400m BLUE: 850mb 0°C Isotherm|
The latest GFS model forecast is showing critical thickness values on the left half of the image above. Critical thickness is a term used by forecasters to deem whether the air is cold enough for snow. Any precipitation above a critical thickness line may be snow- the more critical thickness lines are south of precipitation, the better snow potential there is.
This potential snow event looks to be in the early hours of Monday, roughly around 1 AM central time. All thickness lines, minus the yellow 1000-850mb thickness line, are south of the projected precipitation. Now, this could very well be cold rain or a slight ice event, but I think that cities like Milwaukee have a shot at flakes flying, while Chicago has a lesser potential for such activity. Not a zero chance, but less than areas to the north.
The 6z GFS does show some very slight accumulations in central and southern Wisconsin, but nothing major.
(Caption copy-pasted from COD-NexLab)