Metrorail which so many federal workers rely upon is running only limited underground service from Ballston Monday every 20-25 minutes starting at 7am -
http://www.wmata.com/about_metro/news/PressReleaseDetail.cfm?ReleaseID=6031 Reading into that, doesn't look promising that the federal government will be open. Also Loudoun County also cancelled their commuter bus service for Monday -
https://www.loudoun.gov/index.aspx?nid=221