Flash has the ability to dynamically create and delete symbol instances on the stage by using the Duplicate Movieclip action.

This action takes a symbol instance on the stage and makes an exact copy of it. These duplicate movieclip's have all the properties of the first symbol instance and, once created, can also be deleted using the same action. Although only movieclip's that have been generated using the Duplicate Movieclip action can be deleted from the stage using the RemoveMovieClip action.

To duplicate or remove movie clip instances, use the duplicateMovieClip() or removeMovieClip() global functions.

The duplicateMovieClip() method creates a new instance of an existing movie clip instance, assigns it a new instance name, and gives it a depth, or z-order. A duplicated movie clip always starts at Frame 1 even if the original movie clip was on another frame when duplicated, and is always in front of all previously defined movie clips placed on the Timeline.

duplicateMovieClip(target, newname, depth)
removeMovieClip(target)

ex. this is only one snowflake repeating

download this file (file name: snowing.fla)

download the duplicate movie tutorial (file name: 8dupmovie.fla)
right click on the file (control-click for Mac) and select to download to your drive.