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Posted at 4:45 PM ET, 06/ 6/2010

Alert: Tornado Watch for entire area until 8 p.m.

By Jason Samenow

* Storms spell end to heat wave: Full Forecast | Weather Wall *

watch-area.png
Large area covered by tornado watch.

NOAA's Storm Prediction Center has issued a tornado watch for the entire region and much of the mid-Atlantic and Northeast as a strong cold front interacts with very humid, unstable air over the region. Damaging winds, hail, and an isolated tornado or two could develop with developing thunderstorms this afternoon.

4:45 p.m. update: With the exception of eastern Charles and St. Mary's county in Maryland, most significant thunderstorm activity has now moved south, east and southeast of the metro region (some weaker thundershower activity continues in Stafford and southern Fauquier counties). Skies will gradually clear and cooler, less humid air will settle into the region.

4:00 p.m. update: Tornado warning has expired for parts of Stafford, Culpeper and Fauquier counties. Severe thunderstorm warning in effect for central Stafford and southeastern Prince William counties until 4:15 p.m. and for parts of Charles and St. Mary's county until 4:45 p.m. Winds gusts to 60 mph and ping-pong ball sized hail possible with these storms.

Severe Weather Tracking Station
Warning Text: DC | MD | VA * New: Lightning Map
Radar: Latest D.C. area radar loop shows movement of precipitation over past three hours. Powered by HAMweather. Refresh page to update. Click here to see radar bigger.
LWX Warnings
Warnings: Severe alerts from National Weather Service. Updates w/o refresh (most browsers). Hint: Alert on map? Click matching label in key for details.

Keep reading for more on this watch...

Previous updates

3:30 p.m. update: From National Weather Service: TORNADO WARNING FOR...CENTRAL STAFFORD COUNTY IN NORTHERN VIRGINIA...SOUTHEASTERN CULPEPER COUNTY...SOUTHEASTERN FAUQUIER COUNTY [UNTIL 4 P.M.]. NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A SEVERE THUNDERSTORM CAPABLE OF PRODUCING A TORNADO OVER WESTERN STAFFORD COUNTY...OR 11 MILES WEST OF STAFFORD...MOVING EAST AT 40 MPH. If you're in this area, take cover!

3:15 p.m. update: Tornado warning has expired for Anne Arundel and PG counties. Have not received any report of confirmed tornado (so far). Intense line of storms now headed over Chesapeake Bay towards Delmarva Peninsula where Severe Thunderstorm Warnings are in effect. Elsewhere less organized showers and thunderstorms are producing some downpours and gusty winds scattered throughout the region. A lot of this activity should start winding down over the next couple of hours.

2:45 p.m. update:: Tornado Warning from 2:42 PM to 3:15 p.m. for parts of Anne Arundel County, Prince Georges County including Annapolis and Bowie. Warning text: AT 241 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A SEVERE THUNDERSTORM CAPABLE OF PRODUCING A TORNADO NEAR MITCHELLVILLE...OR NEAR LARGO...MOVING EAST AT 30 MPH. Take cover if you're in this area!

2:30 p.m. update:: Line of storms heading through the District and towards eastern suburbs (Prince George's and Anne Arundel counties). No major damage reports coming in from these storms so far -- though frequent lightning and gusty winds sufficient to take down tree limbs have been reported. We also got a report of some hail on Capitol Hill from Twitter. Follow CWG on Twitter - @capitalweather. Areas that have seen storms already are not out of the woods; more storms are developing to the west (just east of the mountains) and will head east towards the region late afternoon into early evening.

1:45 p.m. update: Severe Thunderstorm warning for northern Fairfax County, DC, and Montgomery county (see map below) until 2:30 p.m. From the warning statement -- NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A LINE OF SEVERE THUNDERSTORMS CAPABLE OF PRODUCING DAMAGING WINDS IN EXCESS OF 60 MPH. THESE STORMS WERE LOCATED ALONG A LINE EXTENDING FROM 5 MILES NORTH OF POOLESVILLE TO COUNTRYSIDE TO 6 MILES WEST OF ASHBURN...AND MOVING EAST AT 45 MPH.

Here is some of the tornado watch text:

TORNADOES...HAIL TO 1.5 INCHES IN DIAMETER...THUNDERSTORM WIND GUSTS TO 80 MPH...AND DANGEROUS LIGHTNING ARE POSSIBLE.

REMEMBER...A TORNADO WATCH MEANS CONDITIONS ARE FAVORABLE FOR 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.

Just an hour or so before the watch was issued, NOAA's Storm Prediction Center posted a discussion describing the favorable environmental conditions for severe thunderstorms and tornadoes here today:

STRONGER DEEP LAYER SHEAR WILL OVERSPREAD MUCH OF THE MIDDLE ATLANTIC...PRIMARILY NO FARTHER SOUTH THAN THE DELMARVA REGION. BOUNDARY LAYER FLOW IS LESS VEERED ACROSS THIS REGION WHICH DOES PROVIDE MORE LOW LEVEL SHEAR FOR POTENTIAL TORNADIC DEVELOPMENT WITH ANY SUPERCELLS THAT MANAGE TO DEVELOP LATER THIS AFTERNOON.
ENHANCED SURFACE HEATING ACROSS CENTRAL VA INTO DE SUGGESTS FURTHER DESTABILIZATION WILL OCCUR PRIOR TO THUNDERSTORM INITIATION RESULTING IN MID LEVEL CAPE VALUES LIKELY EXCEEDING 2000 J/KG. LATEST RADAR DATA SUGGESTS STRONGER FORCING IS BEGINNING TO SPREAD EAST OF THE HIGHER TERRAIN ACROSS MD/WV PANHANDLE AND WITH TIME STRONG UPDRAFTS SHOULD DEVELOP EAST OF THE MOUNTAINS. SEVERE THUNDERSTORM POTENTIAL WILL INCREASE THROUGH THE AFTERNOON HOURS PRIOR TO FRONTAL PASSAGE.

Strong deep level shear suggests lots of rotation in the atmosphere as the wind changes direction with height from surface up to cloud level. This spin in the atmosphere is the rationale for the tornado watch. Also, this discussion refers to a metric known as CAPE - which means convective available potential energy. The more CAPE there is, the more lift and instability in the atmosphere for creating strong updrafts in thunderstorms. We have substantial CAPE quantities today -- which will enhance thunderstorm development and the potential for damaging winds and hail.

Monitor severe warnings issued by the National Weather Service and radar on our Severe Weather Tracking Station above. Also, comment below with conditions where you are.

By Jason Samenow  | June 6, 2010; 4:45 PM ET
Categories:  Alerts, Thunderstorms  
Save & Share:  Send E-mail   Facebook   Twitter   Digg   Yahoo Buzz   Del.icio.us   StumbleUpon   Technorati   Google Buzz   Previous: Forecast: Storms to spell end of heat wave
Next: Tornado Watch discontinued

Comments

Is this the kind of storm where unsecured items outdoors might get thrown around?

Posted by: mmurphy70 | June 6, 2010 1:42 PM | Report abuse

Severe Thunderstorm warnings for Loudoun, Montgomery, DC, northern Fairfax, Arlington, Alexandria, and parts of Howard and Prince Georges. Until 2:30 except for Loudoun. I can hardly wait.

Posted by: Murre | June 6, 2010 1:50 PM | Report abuse

I should learn to read the gang's posts more carefully too.

Posted by: Murre | June 6, 2010 1:53 PM | Report abuse

@mmurphy

Yes-- would secure unsecured items that would be vulnerable to winds in excess of 50 mph.

Posted by: Jason-CapitalWeatherGang | June 6, 2010 1:55 PM | Report abuse

To our north, storm cells have been moving east at 75 mph,. fast even in the winter, but a phenomenal speed in June! Add this forward motion to wind gusts of 35 mph and you get a potential straight-line wind speed as high as 110 mph.

Not sure how this would translate to any tornadoes which might form, but I'd hazard a guess that EF3, possibly EF4 could occur.

Posted by: Bombo47jea | June 6, 2010 1:59 PM | Report abuse

rian and thunder hit downtown Herndon about 5 minutes ago...

Posted by: fsd50 | June 6, 2010 2:04 PM | Report abuse

rain, of course...

Posted by: fsd50 | June 6, 2010 2:05 PM | Report abuse

Thunder now off to the west in Silver Spring.

Posted by: Murre | June 6, 2010 2:06 PM | Report abuse

Some light rain in Centreville VA along with dark skies & some gusty winds.
No thunder/lightning.....yet.

Posted by: FIREDRAGON47 | June 6, 2010 2:15 PM | Report abuse

well, we dodged the bullet friday and saturday afternoons/evenings 'round here, but our pool here in falls church just closed for thunder...how inconvenient...

Posted by: walter-in-fallschurch | June 6, 2010 2:15 PM | Report abuse

Very brief cloudburst in Woodley Park about five minutes ago, but now it's just barely sprinkling.

Posted by: spacecadetkid | June 6, 2010 2:29 PM | Report abuse

spacecadetkid - same here in Logan... looks like we have a break now.. this stuff is moving quickly!

Posted by: Camden-CapitalWeatherGang | June 6, 2010 2:37 PM | Report abuse

Lost power twice in Oakton yet not enough rain to prevent me from having to water.

Posted by: rHairing | June 6, 2010 2:39 PM | Report abuse

I haven't checked in here for quite a while. I was looking at Walter's snow sculptures yesterday. Do you have a summer sculpture endeavor? Topiary?
We had a few big drops in Falls Church, some wind too. Now it's just threatening skies.

Posted by: tbva | June 6, 2010 2:40 PM | Report abuse

Ashburn - wind gusted for about 10 min now everything is calm, barely sprinkles.

Just very hard to get some decent rain out here.

Posted by: LoudounGeek | June 6, 2010 2:40 PM | Report abuse

We've only seen a splatter of rain here in Arlington.

Hubby and I were planning on seeing a 4 p.m. movie in Alexandria. Should we hunker down instead? We're not generally ones to fear the weather, but I don't want to risk our lives either...
(plus, I hate being in a movie when the power goes out...)

Posted by: dinergirl1 | June 6, 2010 2:49 PM | Report abuse

Doppler indicated tornado warning in Anne Arundel PG county

Posted by: rHairing | June 6, 2010 2:49 PM | Report abuse

North Bowie: rain/lightning for about 15 minutes. No hail; winds were gusty, but not too severe

Posted by: Chris737 | June 6, 2010 3:04 PM | Report abuse

Major lightning in College Park at approx 2:30 - 2:45, then a quick rain. Ear piercing boomers. The air still feels electric; lots of car alarms going off. Seems to have passed through quickly. Though the dog is still hiding ...

Posted by: cady123 | June 6, 2010 3:11 PM | Report abuse

Maybe just a quick passing shower in S. arlington. Doppler shows it may have passed. I don't like tornado watches/warnings on a Sunday. I remember that big La Plata tornado happened on a sunday.

Posted by: jojo2008 | June 6, 2010 3:17 PM | Report abuse

well. we're finally had some "weather" here. medium rain and occasional medium thunder and a bit of wind. appears to be done for a while.

tbva,
wow...that's so cool (haha..get it?) that you were looking at them just yesterday. what made you think to do that?! i've threatened to post that link here in the middle of a late-summer stretch of hot, muggy weather. i have done a few sand sculptures. sand isn't nearly as good for sculpting. and it dries out and crumbles pretty quickly.

Posted by: walter-in-fallschurch | June 6, 2010 3:30 PM | Report abuse

walter! I state the obvious. SAND clearly isn't SNOW and has none of the magical qualities.

Posted by: manassasmissy | June 6, 2010 3:34 PM | Report abuse

New tornado warning has been issued.

330 PM EDT SUN JUN 6 2010

THE NATIONAL WEATHER SERVICE IN STERLING VIRGINIA HAS ISSUED A

* TORNADO WARNING FOR...
CENTRAL STAFFORD COUNTY IN NORTHERN VIRGINIA...
SOUTHEASTERN CULPEPER COUNTY IN NORTHERN VIRGINIA...
SOUTHEASTERN FAUQUIER COUNTY IN NORTHERN VIRGINIA...

* UNTIL 400 PM EDT

* AT 329 PM EDT...NATIONAL WEATHER SERVICE DOPPLER RADAR INDICATED A
SEVERE THUNDERSTORM CAPABLE OF PRODUCING A TORNADO OVER WESTERN
STAFFORD COUNTY...OR 11 MILES WEST OF STAFFORD...MOVING EAST AT 40
MPH.

* LOCATIONS IMPACTED INCLUDE...
GLENDIE...
HARTWOOD...
ROSEVILLE...
RUBY...
RAMOTH...
GARRISONVILLE...

PRECAUTIONARY/PREPAREDNESS ACTIONS...

TAKE COVER NOW. MOVE TO AN INTERIOR ROOM ON THE LOWEST FLOOR OF A
STURDY BUILDING AND AVOID WINDOWS. IF OUTDOORS OR IN A MOBILE HOME OR
VEHICLE...MOVE TO THE CLOSEST SUBSTANTIAL SHELTER AND PROTECT
YOURSELF FROM FLYING DEBRIS.

Posted by: Andrew-CapitalWeatherGang | June 6, 2010 3:36 PM | Report abuse

Hi Walter....I was sweltering after working in the yard....saw the bookmark of your page and relived the winter temps.

Posted by: tbva | June 6, 2010 3:50 PM | Report abuse

First line of storms brought a few raindrops and grey skies to Vienna and Oakton - now we're getting some thunder from a potential second wave. Definitely cooler and more comfortable, regardless.

Posted by: PSUMarkDC | June 6, 2010 3:52 PM | Report abuse

Centreville VA Much cooler & dryer air current temp 79. Consistent not so distant thunder to the south. Some sunshine; earlier rain wasn't measurable.
That seemed too easy an end here to a really prematurely hot n muggy stretch of weather. Not a complaint!

Posted by: FIREDRAGON47 | June 6, 2010 4:07 PM | Report abuse

Other than five drops of rain and a brief power outage, nothing happening in Glover Park. Another melodramatic NWS forecast that fizzled out for most of the region (though I hope that no one is getting really severe weather where they are).

Winter, spring, summer, fall, all you gotta do is stall, and the NWS will blow another forecast.

Posted by: JerryFloyd1 | June 6, 2010 4:24 PM | Report abuse

>Another melodramatic NWS forecast that fizzled out for most of the region

Between 2:20 and 2:35, close cloud to ground lightning and very very heavy rain in Silver Spring. I was trying to make it to a friend's performance, was running late, got on the outer loop. The outer loop was really slow so I immediately exited to head home. I was only a half-mile away from the beltway when the skies opened up and buckets of rain came down preceded by gusts of wind blowing many leaves off trees. It ended almost as quickly as it began.

Posted by: Murre | June 6, 2010 4:57 PM | Report abuse

Hey Gang--the PostLocal banner is claiming "Tornado Warning for local area until 8pm." You might want to give the front-web-page people a tutorial on the differences between a watch and a warning!

Posted by: jkuchen | June 6, 2010 5:08 PM | Report abuse

Just to clarify--it's the "On PostLocal" smaller banner that appears on the front national page immediately above the lead photo and headline, not the bigger PostLocal banner that's closer to the "masthead."

Posted by: jkuchen | June 6, 2010 5:12 PM | Report abuse

Why mention it all? Whatever ingredients that existed for a possible tornado are long gone. The front has passed and the temperature is 72 degrees. There is NO longer a chance for a tornado in the metro area.

What is the sense of having a banner headline at 5:35pm when the storm passed three hours ago?

I say its to cause alarm and draw clicks to the site.

Posted by: MKadyman | June 6, 2010 5:36 PM | Report abuse

@MKadyman and @jkuchen

The appropriate folks have been notified about this and it has been fixed. Working on getting everyone up to speed on the difference.

Posted by: Jason-CapitalWeatherGang | June 6, 2010 5:42 PM | Report abuse

It's still not fixed on the regular WaPo home page - first link under "News Columns and Blogs" in the section "above the fold".

Posted by: PSUMarkDC | June 6, 2010 6:09 PM | Report abuse

The comments to this entry are closed.

 
 
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