UPDATE: My observer aboard MARC reports that the train that had  been stalled reached Penn  Station about 25-28 minutes late. She said the Amtrak crew was courteous and communicative about what was happening, but the air-conditioning never did work properly.

REPORTED EARLIER: A source aboard MARC says a northbound Penn Line train was stalled about 10 minutes outside Union Station without air-conditioning before power was restored 15 minutes later. The MTA said the problem was with the Amtrak-owned overhead power supply but that the train is moving again -- but slowly.

Amtrak must have learned something from the June 21 fiasco. My source says there is water aboard -- not cold, but at least it's something.

Here's an update from aboard: "After approx. 15 minutes, the lights came on, followed by the A/C. 10 minutes later, we started moving. We traveled maybe 2 miles before the lights and A/C went out again, but we kept moving. As I write this sentence, we are approaching Bowie at speed."