Folks, there were some nasty storms rolling through DC this evening. There were a bunch of delays and cancellations. Flightaware is showing 83 cancellations for DCA today. If that's not weather related, I don't know what is.
The MARC train is only $6 up to BWI from Union Station. I just took it today. It was raining like crazy at Union Station (I was on train 430 which departed at 4:20PM).
FYI. MARC trains don't run on weekends. You'll have to take regular Amtrak which will be $18-$23.