Snow has been falling all night and all day. However, when Carter chases and confronts Del Amico on the El platform, there is no snow on the El or on the streets below them.
At 37:07, in the hallway, a man in a gray coat and scarf walks by Dr. Carter, Dr. Del Amico, and Chase. At 37:16, he walks by again, going in the same direction.
When Carter slips and falls walking in the ambulance doors you never hear the food containers or bags hit the ground spilling all the contents which is clearly visible when they show the close up of him on the floor. The styrofoam containers would have made some slight cracking sounds as they hit the floor.
In the beginning of episode#4.13 in the staff lounge, Doug Ross places his coat in a locker with a big band aid sticker on it. At end of episode the locker with the big band aid has Carter's name on it.