Where is an artifact during post-processing?

I created an Ant target to run during post processing of an artifact build.  It copies the artifact from the "out" sub directory to another location on disk where it is actually launched.  However, when the post-processing occurs,  the artifact hasn't yet been placed in the out directory, so it can't be copied (or the previous version is copied).

I've verified this by testing to see when the artifact jar appears, and it appears AFTER the post-processing step completes.

Where is the artifact during post-processing?  How can I ever do anything with it if I can't get to it?  I dumped all the parameters in the post processing environment (echoparameters) and didn't see anything that looked like a reference to it.