How can I get notifications to pop up in my active display?

I have an MBA running Yosemite. Apps like Mail, messages, calendar, and FaceTime have 'banner' notifications that pop up in my laptop's built-in display but they don't pop up on my external monitor that's plugged in via a thunderbolt adapter.

How can I get notifications to display on my active display?

Is this even possible or a feature that is yet to be implemented by Apple?