Green card Interview done, when can i expect the confirmation via MAIL (POSTAL SYSTEM

[daddyhood]

Hi all,
I applied via AOS i485. EAD and Advance parole received in the first week of October 2015 (i had applied first week august 2015)
My green card interview was on the 7th of december 2015, and went pretty well. But of course i am awaiting the decision via post. I want to travel to canada for christmas as i already have the advance parole. what is your recommendation? and if anyone has similar dates please share your experience.
thanks

[burkinamer]

AOS Interview in NYC - December 8, 2015

Text/E-notification of Approval - December 8, 2015

Received Welcome Letter via snail mail- December 12, 2015

Green card received - December 15