Even though temperatures aren't expected to drop below freezing Friday night, it can still snow. According to the Weather Blog, the answer is dry air:
The precipitation will fall into this dry air and evaporate. As it evaporates, it cools the air and this gives Louisville a window when snow could fall. As I see it, that window is late Friday through around 6 am on Saturday and then we go to rain. That window stays open for southern Indiana through mid morning when you will go a rain-snow mix.
According to WDRB Meteorologist Rick DeLuca's Friday morning forecast, southern Kentucky will receive more rain than snow, but southern Indiana could get from one to three inches of snow.
Stay up to date with continuing forecasts throughout the day on the WDRB Weather Page, Weather Blog and Facebook Page.