Flash flood warnings are posted tonight across most of western Maryland as torrential rains continue to pound the region. Emergency officials were investigating a suspected tornado, which damaged structures earlier this evening down in Chaptico, in St. Mary's County. Voluntary evacuations are also taking place along portions of the bay shore in Anne Arundel and Baltimore counties as abnormally high tides cause minor to moderate coastal flooding.

The forecast map shows a broad swath of flood-warned areas. Water vapor images from space show plenty of moisture continuing to stream north across the state, from Washington County east to Carroll, and south the Montgomery and Prince George's.

The heaviest rains - described as "torrential" - appeared to be falling in the Catoctins, according to the weather service. Flooding was expected in Wolfsville, Pleasant Walk, Bolivar and Arnoldtown. Heavy rain was also reported this evening in Rockville, Emmitsburg and Mt. Airy.

"Significant" rises were reported in the Potomac and Rappahannock rivers. Little Falls, on the Potomac, was expected to surpass flood stage by Thursday morning and runoff from the rains flowed out of the tributaries and reached the main stem of the river. The Potomac was expected to rise above flood stage at Wisconsin Avenue in Washington by Thursday night.

Two to 4 more inches of rain were forecast tonight for Prince George's County, including Upper Marlboro, New Carrollton, College Park, Beltsville and Hyattsville (which saw some of the heaviest rain over the past four days -more than a foot).

All that said, it doesn't look - at least from the radar image - that this rain can last long into the morning. The echoes seem to be closing in on our region, with drier air close behind. By this time Wednesday, we're going to be much more focused on rising rivers than rainfall.