At one time this was allowed. All you had to do was pay a small prorated amount to upgrade just for the remaining time left on the original AP. But no longer.
They will now treat this like any other upgrade in that they will give you a dollar credit for the unused portion of the AP to apply towards the purchase of a brand new PAP that will run one year from the day of the upgrade. In your case since it's the last week you pass is valid, you'll probably get about an $8 credit (+/- a few cents).