You can take either Amtrak or Marc Commuter service from the BWI Rail Station to Union Station in DC. You will need to take the shuttle bus from Baltimore Washington Airport to the rail station (about a 10 - 15 minute trip) before continuing on to DC.

You will find further information and links to schedules at: http://www.bwiairport.com

Hope the weather gets a bit warmer so you can enjoy your weekend in DC!

Winnie Alexandria, VA