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Posted at 06:15 PM ET, 06/12/2011

Strong storms move away from region; drier, cooler air moving in

6:15 p.m. update: The Severe Thunderstorm Watch that had been in effect until 8 p.m. for the entire metro region has been canceled from the District and to the north and west. To the southeast and east, where the watch remains in effect, storms will move away by 8 p.m. when the watch expires. Much cooler, drier and air is now filtering into the region. A sunny, pleasant Monday is on tap - with low humidity and highs 75-80. See Brian Jackson’s full forecast into next week for more details.

Storm Reports: Trees knocked down in Vienna (near Dunn Loring, onto house), Centreville and Clifton in Fairfax county according to National Weather Service.

Commenter SeahawkDad reports: “That was one hell of a storm that formed up over south western Loudoun and headed south east along Route 50. We were in Upperville when it hit and two of the routes North to Purcellville were blocked by downed trees. Finally had to go all the way to 15 to find a clear path North.”

5:45 p.m. update: Storms are slowly working their way out of southeast Fairfax county and mainly concentrate across Prince William county and into extreme southern Prince George’s county and Charles county where there’s a Severe Thunderstorm Warning until 6:30 p.m. La Plata and Port Tobacco River are in the path of this storm which may produce quarter size hail and winds to 60 mph.

5:30 p.m. update: If you live along and south of I-66 in Fairfax county, you have seen heavy rain and storms. To the north and northeast extending into NW DC and southern Montgomery county, you missed out it appears. The most intense activity currently stretches across the northern half of Prince William county into southeast Fairfax county. This entire area of storms is headed towards southern Prince George’s and Charles counties.

Overview (from 2:15 p.m. - no longer valid): A Severe Thunderstorm Watch is in effect until 8 p.m. for the entire metro region, as an incoming cold front clashes with warm and humid air . From the Storm Prediction Center:

HAIL TO 1.5 INCHES IN DIAMETER...THUNDERSTORM WIND GUSTS TO 70 MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE IN THESE AREAS.

Follow live updates via our Twitter feed above. And monitor radar and severe warnings below. Keep reading for earlier updates & technical discussion from the Storm Prediction Center.

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Earlier updates:

5:10 p.m update: Severe thunderstorm warning for southern half of Fairfax county, northeast Prince William, southwest Prince George’s and northwest Charles county until 5:45 p.m. In path: Burke, Springfield, and Ft. Belvoir. Quarter size hail and winds to 60 mph possible with these storms.

5:00 p.m. update: While the most intense activity remains in western Fairfax county, some storms are finally popping up around/inside the beltway - including a cell near Tysons, in the District, and near Suitland.

4:45 p.m. update: Amazingly, yet again, the storms that were headed towards D.C. are breaking up. Many areas inside the beltway may be bypassed as the strongest activity passes to the south and north. D.C. split rears its ugly head again.

4:30 p.m. update: Strongest activity is currently in SE Loudoun county moving into northwestern Prince William and southwest Fairfax county. Activity to the north and northeast is broken, with one stronger cell into north central Montgomery county. Video from Twitter follower @dalison: T’storm in eastern Loudoun.

4:10 p.m. update: It doesn’t look like this line of storms - which now extends from NW MoCo through central Loudoun into western Fauquier co - is going to miss. A new severe t’storm warning is in effect for eastern Loudoun, southwest Fairfax, western Prince William and northern Fauquier county through 4:45 p.m. Hail as large as half dollars and winds to 60 mph are possible with these storms which look to impact the Plains, South Riding, Dulles airport, Centreville, and Chantilly. The storms are about an hour from the north and west side of the beltway.

4:00 p.m. update: Storm in Loudoun county - nearing Leesburg - has history of wind damage (reports of power lines down in Lovettsville) and likely also contains hail. This storm is about 45 minutes from western Fairfax county.

3:30 p.m update:Broken line of severe storms extends from north central Frederick county to the western border of Loudoun county. Severe thunderstorm warnings are in effect for the southern two-thirds of Frederick county and the western two-thirds of Loudoun county until 3:45 p.m and 4-4:15p.m., respectively. Wind gusts to 60 mph and hail are possible with these storms. Montgomery county is likely to be impacted by theses storms between 4 and 5 p.m. (west to east), and Fairfax county between 4:30 and 5:30.

2:15 p.m. update: Strong to severe thunderstorms are developing along a cold front in Pennsylvania into eastern West Virginia and advancing southeast. The most likely timing for storms in the D.C. metro region ranges from 3 p.m. in the far NW suburbs (Frederick county) to 6:30 p.m. in the SE suburbs (Calvert and St. Mary’s county, assuming it holds together). The most likely time for storms inside the beltway is between 4:30 and 6:00 p.m. - however, isolated storms may develop prior to that. At the moment, some isolated storms are affecting Charles and Calvert counties. Not everyone will see storms and changes in this timeline are possible.

Technical Discussion from the Storm Prediction Center:

DISCUSSION...THUNDERSTORMS ARE STRENGTHENING ALONG THE COLD FRONT IN PA...AND ADDITIONAL DEVELOPMENT IS BEGINNING FARTHER TO THE S/SW OVER THE HIGHER TERRAIN AND IN THE OPEN WARM SECTOR. STRONG SURFACE HEATING IS SUPPORTING MLCAPE VALUES OF 1500-2000 J/KG...WHILE VERTICAL SHEAR IS SUFFICIENT FOR ORGANIZED CLUSTERS FROM NRN VA INTO PA. FARTHER S...THE ENVIRONMENT IS MORE FAVORABLE FOR PULSE TYPE SEVERE STORMS WITH DAMAGING OWNBURSTS...GIVEN THE WEAKER VERTICAL SHEAR AND STEEP LOW-LEVEL LAPSE RATES. DAMAGING WINDS WILL BE THE MAIN SEVERE THREAT...THOUGH MARGINALLY SEVERE HAIL WILL ALSO BE POSSIBLE IN THE STRONGER STORMS.

By  |  06:15 PM ET, 06/12/2011

Categories:  Thunderstorms, Forecasts

 
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