When the data becomes more secure (less variables.) As of now, NBC5 says 1 inch on Mon and maybe another inch or 2 Tue/Wed. Nothing major. Now if the bulk of the storm moves further north, expect a waiver, but as of now, they expect the big snow to be south and east of the city (and ORD is in the opposite direction of that.) Maybe Midway will get more.

http://www.nbcchicago.com/weather/