Flood warnings in Montgomery and Prince George's counties and flood watches for the Baltimore area are in effect this morning as rain falls intermittently throughout much of Maryland and Northern Virginia.

The National Weather Service issued an advisory at 6:15 a.m., saying that up to two inches of rain had fallen on southern Montgomery County and northern Fairfax County in the previous three hours. The agency said additional heavy rains were likely as storms moved repeatedly over the same areas.

The downfalls, which persisted in the greater Baltimore area shortly after 9 a.m., made rush-hour driving hazardous in some places, although few serious accidents were reported.

An exception was a crash reported at 7:44 a.m. by the State Highway Administration. The accident, on Interstate 97 in Anne Arundel County, forced the closure of all the highway's southbound lanes as well as the ramp leading to Route 100. Maryland State Police reported 30 minutes later that the ramp and two lanes had reopened.

A state police spokesman also reported an earlier crash, at 5:50 a.m., in the northbound lanes of I-95 near its intersection with Route 100. All lanes were reopened 30 minutes later, he said.

Police dispatchers in Baltimore, Howard, Harford and Carroll counties said they were aware of no accidents they could attribute directly to the weather. The NWS issued a flood watch for Baltimore and the counties until 3 a.m. Thursday.

nick.madigan@baltsun.com