Blizzard poster Rishgur has announced emergency maintenance for select realms, starting at 3:00 a.m. PDT / 6:00 a.m. EST Friday morning and lasting approximately four hours until 7:00 a.m. PST / 10:00 a.m. EST.
There is no indication as to what this maintenance corrects, and there hasn't been any widespread reports of realm or connectivity issues (at least that we've heard). So who knows why the realms are getting fixed tomorrow morning, but they are.
The realms will remain active and playable during this maintenance, but some stability issues may occur!
The maintenance appears to involve multiple battlegroups. The specific realms include the ones listed below and after the break.