Tornado watch dropped for metro region

By Jason Samenow

Showery through the afternoon

1:50 p.m.: The tornado watch has been dropped for the southeast suburbs (Prince George's, Calvert, Charles, and St. Mary's counties)

1:40 p.m. update: At least one report of damaging winds has come in from Prince Frederick in Calvert co. where a tree came down on a power line.

1:30 p.m. update: The tornado watch has been canceled for the entire metro region except southern Maryland where it should be dropped soon. Though some areas experienced ominous skies, heavy downpours and gusty winds, I have yet to see any reports of severe weather. The early onset of the storms limited their intensity. Although the cold front won't come through until later and more rain showers are possible through the evening commute, severe storms aren't likely to develop as the atmosphere has stabilized quite a bit from the recent rain. Temperatures should generally be around 60. Gusty winds and colder air move in tonight. Ian will have more in his PM Update around 3:30 p.m.

Keep reading for earlier updates...

Basic information: Due to the potential for severe thunderstorms which may produce a few tornadoes in the region, NOAA's Storm Prediction Center has issued a tornado watch through 4 p.m. for points south and southeast of the District. Previously the watch was in effect for much of the metro region but at 11:31 a.m., the watch was discontinued for Montgomery, Howard, Loudoun, and Frederick counties in Md. The watch was then canceled for the District and western suburbs in Va. at 12:40 p.m and the southeast suburbs at 1:50 p.m.

The most likely timing for storm activity to impact the metro region is late morning to around noon in the northwestern and northern suburbs and noon through the late afternoon and evening elsewhere. However, a few storms could break out ahead of this line, affecting areas in the immediate metro region around or even prior to noon. During the afternoon, additional storms likely fire up behind the initial line that passed through the north and northwest suburbs.

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Earlier updates:



1:15 p.m update: The threat of severe weather has largely cleared the region. The severe t'storm warning that had been in effect in eastern suburbs has been canceled. On and off showers are now likely through the evening commute, but not should reach severe levels.

12:50 p.m. update: The tornado watch has been canceled except for counties east and southeast of the District - i.e. Calvert, Charles, Prince George's and St. Mary's counties.

12:40 p.m. update: Severe thunderstorm warning issued for storm (mentioned below) over extreme southern Prince George's, Charles and St. Mary's co until 1:30 p.m.. These storms are rapidly heading toward Chesapeake Bay, but may produce some gusts to 60 mph before exiting the region.

12:35 p.m. update: The strongest activity has passed east of the District and stretches from southern Prince George's county through western Charles county (and somewhat into eastern Stafford county). Though heavy rains and gusty winds are accompany the activity, no warnings are in effect. That means the threat of severe weather has diminished from D.C. and points west. However, rain showers remain possible through this evening.

12:10 p.m. update: South and southwest of the beltway in southern Fairfax county, central Prince William county and southern Fauquier county, the line of storms is intensifying. Heavy rain and strong winds are likely with this line of storms as it moves east toward Alexandria, southern Prince George's county, and Charles county.

12:00 p.m update: While the north and northwest suburbs are no longer under a tornado watch, it has has been extended southeast to include Calvert and St. Mary's county.

11:45 a.m. update: Heavy rain showers have raced into eastern Fairfax county and will enter NW D.C. in the next 15 minutes. More showers and storms to the southwest will approach and move through the southern suburbs in the next hour. Still no reports of severe weather, and the likelihood of much materializing is lowering. The best odds of severe now look to be from Fredericksburg and to the south and southeast.

11:35 a.m. update: Tornado watch canceled for Montgomery, Loudoun, Frederick and Howard counties

11:30 a.m. update:: Still not seeing any severe weather, just some heavy rain and gusty winds - mainly in Loudoun county and northern Fauquier county. This activity will continue racing northeastward, affecting Montgomery county and possibly western Fairfax county during the next 30 minutes. The rain/storms may impact eastern Fairfax county and the District between noon and 1 p.m. before heading toward the eastern suburbs.

11:10 a.m. update This northern branch of the squall line impacting Loudoun and western/central Montgomery county has weakened quite a bit, though some downpours and gusty winds have been reported. This activity is racing off to the northeast and may miss a good part of Fairfax county and the District. These areas and especially points south are those to watch for the development of stronger activity early this afternoon as temperatures have spiked well into the 60s and even the low 70s, potentially destabilizing the atmosphere. There is still a lot of activity to the west and southwest to monitor as it advances northeast over the next few hours.

10:45 a.m. update: Storms have now reached extreme western Montgomery county and are impacting Leesburg in Loudoun county. The good news is that the line of storms has weakened and no severe thunderstorm warnings are in effect. However, heavy downpours and gusty winds to 30 mph are likely with these storms. This line of storms should head through Montgomery county in the next 45 minutes to hour. In Fairfax county, the storm should arrive in 30-45 minutes and reach the beltway by around noon. The storms, if they hold together, could impact the District by lunchtime. This line of storms is likely to be followed by additional activity later this afternoon.

10:20 a.m. update: These storms are flying to the east around 65 mph - and headed toward the metro region sooner than anticipated earlier today and last night. Frederick county will experience strong storms in the next 45 minutes and they will bear down on northwest Montgomery county shortly before 11 a.m. To the south, northwest Loudoun county will get hit by strong storm in next 30 mins, line to near Dulles in about an hour.

9:45 a.m. update The northeastern edge of the squall line is already producing intense storms in West Virginia panhandle, extreme northwest Virginia and Washington county in Maryland where a Severe Thunderstorm Warning is in effect until 10:30 a.m.. The warning extends into western Frederick county as well and should impact Frederick itself in another 45 minutes to hour.

9:05 a.m update: Due to the potential for severe thunderstorms which may produce a few tornadoes in the region, NOAA's Storm Prediction Center has issued a tornado watch through 4 p.m. for much of the metro region, except the southeast suburbs.

Currently, a strong squall line stretches from western Maryland to eastern Kentucky (see regional radar). This is the line to monitor, as it advances northeast late this morning and this afternoon.

Here are some of the key excerpts from SPC's watch statement:



Area covered by tornado watch

TORNADOES...HAIL TO 0.5 INCH IN DIAMETER...THUNDERSTORM WIND GUSTS TO 70 MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE . . .



TORNADOES AND SEVERE THUNDERSTORMS IN AND CLOSE TO THE WATCH AREA. PERSONS IN THESE AREAS SHOULD BE ON THE LOOKOUT FOR THREATENING WEATHER CONDITIONS AND LISTEN FOR LATER STATEMENTS AND POSSIBLE WARNINGS.

DISCUSSION... QUASI LINEAR CONVECTIVE SYSTEM [i.e. squall line] CURRENTLY MOVING THROUGH THE CENTRAL APPALACHIANS IS EXPECTED TO MOVE EAST OF THE BLUE RIDGE BY LATE MORNING. AIR MASS EAST OF THE HIGHER TERRAIN IS CHARACTERIZED BY STEEP MIDLEVEL LAPSE RATES AND A WARMING/MOISTENING BOUNDARY LAYER. GIVEN THE STRONG VERTICAL SHEAR IN PLACE...SETUP WILL REMAIN FAVORABLE FOR EMBEDDED BOWING AND/OR SUPERCELL FEATURES WITH THE THREAT FOR DAMAGING WINDS AND PERHAPS A TORNADO OR TWO.