So we had some light snow in the area today and coming home tonight from work, the roads were a bit wet and the car ended up with a light coat of grime from the drive. I noticed once I got off of the highway and into stop/go conditions, that I could see a flash in the rear view mirror when I applied the brakes. I am not sure if this is something new and I hadn't noticed or if it's been going on and I am noticing tonight since the rear window had a coat of road grime on it. Any ideas? The car appears to be normal - no alerts, dash lights, etc.
I searched and only saw references to emergency breaking causing something similar and I am not doing any emergency breaking.