Need help with falling snow effect

Hi, I’m trying to create a Flash animation where there are photos of people in the middle and I want to put snow falling on both sides but not in the middle, so as not to cover their faces. I followed the Kirupa falling Snow tutorial (http://www.kirupa.com/developer/mx/snow.htm) and it came out beautiful, except the snow falls in the middle as well as the sides.

How do I make it fall just on the sides? PLEASE HELP!