While an isolated shower can't be ruled out overnight, those that are getting in line at stores Friday morning will be dry. Temperatures will be in the mid-30°s as stores open.
Temperatures will be slow to rise through the day due to cloudy skies. Temperatures will eventually top out in the low/mid 40°s.
If you are going to Monument Circle in downtown Indianapolis for the Circle of Lights program plan on temperatures to be around 40° with cloudy skies.
I think Circle of Lights should be able to get in before rain arrives. However, if you're out late Friday night, expect rain showers to start falling. At this time it appears rain will start to move in to central Indiana - from the west - after 10 p.m.
Rain will intensify overnight in to Saturday morning. Heavy rain could fall at times through the morning and in to the afternoon. I think the intensity of the rain will start to decrease later in the afternoon and in to the evening.
Computer models suggest rainfall totals could be hefty. A three computer model average suggests 1.37" of rain in Indianapolis through 8 p.m. Saturday.
The highest rain totals should be over the southern third of the state. As you can see in the above image, some areas could receive in excess of 2". Localized flooding is not out of the question.
Rain will come to an end by early Sunday morning. In fact, we will likely see a few hours of sunshine Sunday morning before clouds move back in late morning/early afternoon. Along with the clouds, temperatures will be falling from the low 50°s shortly after midnight Sunday to the 30°s by Sunday afternoon.
Rain will return to central Indiana Sunday afternoon and the rain will change over to snow showers. Snow showers could linger as late as early Monday morning.