Amtrak and MARC Penn Line service has been suspended between Baltimore and D.C. since 7:45 a.m., thanks to a major water main break affecting tracks between the BWI Thurgood Marshall Airport and Baltimore Penn stations. Amtrak reports that tracks in the area are covered with mud, trees and other debris. Service restoration is not expected until at least noon today, and could be hours later. There’s literally no alternative rail service between the two cities, so if you had plans to travel north from D.C. via train this morning, you ought to look into a bus. You can call 800-USA-RAIL for train status updates later in the day.