North American realms are now going down at 5 a.m. PST and will be offline for an unscheduled 4 hour maintenance window.
Original Post at 8:44 p.m. PST:
Only announced within the last few minutes, European realms will be going down imminently for an unscheduled 4 hour maintenance window.
[EU] We'll be performing maintenance on all EU realms beginning at 7 am CEST & lasting approximately 4 hours: http://t.co/xMzRuJKE0h- World of Warcraft (@Warcraft) November 14, 2014
Though wholly undesirable by most players, an emergency maintenance period may turn out to be the best way to get realm stability issues under control.