Flash flood warning for District discontinued
Though tornadoes did not materialize overnight, the atmosphere remains humid and unstable and thunderstorms capable of rotating may once again develop this afternoon. The Storm Prediction Center has issued a tornado watch for much of the metro region (map) until 8 p.m., excluding the far western suburbs.
2:55 p.m. update: The tornado watch has been canceled for Prince William, Fauquier, Fairfax, and Montgomery counties as well as the District. But the watch remains in effect in Prince George's and Stafford counties, as well as bordering counties to the south and east. Also, the flash flood warning that had been in effect for the District and close-in suburbs has been discontinued.
Remember that a tornado watch is issued when weather conditions are favorable for severe thunderstorms to produce tornadoes in and close to the watch area. It is not a guarantee that tornadoes, which are relatively rare in this area, will form.
2:40 p.m. update: With the exception of Charles county, where some thundershowers linger, the rains have ended across the metro region. There's a 40% chance of additional activity the rest of the afternoon and evening, with the best storm chances east of D.C. towards the Bay.
Keep reading for earlier updates...
From 2:00 p.m.: Though a Flash Flood Warning remains in effect for the District and close-in suburbs, the rain has stopped for the time being across much of the area except the east and southeast suburbs. A nasty thunderstorm continues to impact northern Charles county and southern PG county, where a severe thunderstorm warning remains in effect until 2:15 p.m. This storm should move into Calvert and Anne Arundel counties in the next 30 minutes.
Everyone else in the metro region should catch a break for the next hour or two, but it's not out of the question additional showers and storms develop late this afternoon into the early evening.
From 1:30 p.m.: A severe thunderstorm warning has been issued for southern Prince George's county and northern Charles county, including La Plata until 2:15 p.m.. Weather service says storm could produce winds in excess of 60 mph. The storm in northern Charles county is the most intense so far today and has the potential to rotate and generate a tornado - though no tornado warning has yet been issued. Stay tuned.
From 1:15 p.m.: The story with the storms so far has been the rain not the wind. Doppler estimated rainfall totals suggest 0.75-1.25" has fallen from central Prince William county through central Fairfax county and into downtown D.C. in under an hour. These heavy rains have prompted the issuance of a Flash Flood Warning for the District and immediate close-in suburbs (Arlington, E Central Fairfax, SE Montgomery and W Central PG counties, Alexandria, and Falls Church)
The current line of storms is progressing to northeast with the strongest activity in extreme eastern Prince William and Fairfax counties. This activity is headed into southern Prince George's county. In the next 45 minutes or so, the District and points to the south and west should see the rain stop or mostly diminish - at least for the next couple hours.
From 12:45 p.m.: A line of thunderstorms with locally very heavy rain is covering Fairfax county, the District, western Prince George's county, and eastern Montgomery county. The line then extends southwest into western Prince William and eastern Fauquier counties. This line is moving northeast, with some areas getting "trained" by multiple storms within this same line. Thus, localized flash flooding is possible. So far, no tornadoes have developed.
From 12:15 p.m.: Strong thunderstorms - with torrential rain - are currently moving through western Fairfax county and will head northeast impacting D.C. and Montgomery County in the next hour. So far, these storms have not produced reports of severe weather and no warnings have been issued. But storms may grow more intense this afternoon - especially east of I-95.
From 11:55 a.m.: NOAA's Storm Prediction Center has just issued a special statement [bold text indicates emphasis added] that it is:
MONITORING FOR AN INCREASING SURFACE BASED SEVERE POTENTIAL THIS AFTERNOON WITHIN A SOUTHWEST-NORTHEAST CORRIDOR FROM NORTHERN NC AND CENTRAL/EASTERN VA INTO DE/EASTERN MD AND NJ/SOUTHEAST PA. A TORNADO WATCH WILL BE COORDINATED SOON.
MODERATE LOW LEVEL TURNING AND OTHERWISE RATHER STRONG DEEP LAYER SOUTHWESTERLY FLOW WOULD BE VERY SUPPORTIVE OF BOTH SUPERCELLS AND SMALL SCALE BOWING SEGMENTS...WITH ASSOCIATED POTENTIAL FOR WIND DAMAGE/TORNADOES.