Update at 3:00 p.m. — A Flash Flood Warning has been issued for Arlington, D.C., Alexandria and Fairfax County. The National Weather Service says very heavy rain has produced the imminent risk of flash flooding around streams and low-lying areas.

A Tornado Watch has been issued for Arlington and the surrounding region.

The National Weather Service says weather conditions are conducive to the formation of tornadoes.  The watch is in effect until 10:00 p.m.

From an earlier weather advisory:

A FLASH FLOOD WATCH IS IN EFFECT FOR THE OUTLOOK AREA UNTIL MIDNIGHT. EPISODES OF HEAVY RAINFALL WILL LEAD TO FLASH FLOODING IN SOME AREAS…PARTICULARLY THIS AFTERNOON AND EVENING.

IN ADDITION…SOME THUNDERSTORMS MAY BECOME SEVERE DURING THE AFTERNOON AND EARLY EVENING. THE PRIMARY THREAT WILL BE DAMAGING WIND GUSTS…HOWEVER A FEW TORNADOES ARE POSSIBLE.