How to force snapshot version for certain branches

I'm trying to implement a configuration of the release plugin such that certain branches *always* produce a snapshot version.

For example, any branch matching 'PR-.*' must produce a snapshot version, even if it is on a release tagged changeset.

I am aware of the property 'release.forceSnapshot' however I'd like to effectively apply this option programmatically from within scmVersion configuration depending on branch.

Can anyone help if this is possible, and how one might go about it?

Thanks!