Around 4-5 AM AKST going off what I see others have been saying, sorry I don't know precise timestamps. One of the posts in /r/alaska was at 4:50 AM. One in /r/anchorage was at 4:39 AM.
Edit: Alaska Volcano Observatory just posted this graph of the pressure wave here
Edit: Alaska Volcano Observatory just posted this graph of the pressure wave here
https://www.facebook.com/alaska.avo/posts/296707312495753