Update 3:47 p.m.:
A good news update - it looks like the numbers of those without power have gone down dramatically in the last half hour or so.
Updated 3:18 p.m. with approximate boundaries of outage - map below
A planned power outage, announced Wednesday afternoon by Ameren, has, at our last check just before 3 p.m., affected approximately 4,800 people in the Missouri portion of the St. Louis area.
The outage was necessary, Ameren said in a statement, to make repairs following a cable failure Tuesday night. Those repairs, Ameren said, are being made to "prevent a more widespread and extensive outage."