Travelling abroad while waiting for GC

[popple]

I am referring to after the GC interview. I have my interview in March, and am travelling to Britain in June for a family wedding. I was expecting my application to taker longer ad have applied for advanced parole.

If my interview is successful and I am approved for a GC, but the actual card is not through the mail in time to travel, how can I legally re-enter the coutry.

TIA