I really suggest you look over this code, it looks as if your just trying to take examples and put them together. You should learn how this code works and why it works. Also try stuff from scratch, if I'm wrong though I apologize.
What I'm doing here is just adding another if statement to each snowflakes individual EnterFrameFunction event handler function. A simple hitTestObject method works fine in your case.
Please review it and ask questions if you don't understand how this works.