Alert archive / Virginia / Mesoscale Discussions in 2011

Mesoscale Discussion 264

March 23, 20117 counties in Maryland; 22 counties in Virginia

The Storm Prediction Center issued this mesoscale discussion at Mar 23, 2011, 8:13 PM EDT for 7 counties in Maryland; 22 counties in Virginia. It was in force for 92 min.

The area

The outline as issued.

The facts

Issued: Mar 23, 2011, 8:13 PM EDT (00:13 UTC)
Expired: Mar 23, 2011, 9:45 PM EDT
In force: 92 min
Issued by: the Storm Prediction Center

All 29 counties

Anne Arundel County, MD, Baltimore County, MD, Charles County, MD, City of Baltimore, MD, Howard County, MD, Montgomery County, MD, Prince George's County, MD, Albemarle County, VA, Arlington County, VA, City of Alexandria, VA, City of Charlottesville, VA, City of Fairfax, VA, City of Falls Church, VA, City of Fredericksburg, VA, City of Manassas, VA, City of Manassas Park, VA, City of Waynesboro, VA, Culpeper County, VA, Fairfax County, VA, Fauquier County, VA, Greene County, VA, King George County, VA, Loudoun County, VA, Madison County, VA, Orange County, VA, Prince William County, VA, Rappahannock County, VA, Spotsylvania County, VA, Stafford County, VA

The radar

The Sterling radar (KLWX), 34 km from the middle of the area, began a volume at 00:13 UTC, the scan nearest the moment this went out.

Open the radar archive at this moment

The archived warnings, watches and discussions in force at that minute are drawn over the scan, this one among them.

The nearest sounding before it

Washington/Dulle, VA (KIAD), launched 00:00Z, 0.2 hours before the alert went out and 35 km from the middle of its area. This is the routine balloon launch nearest before it, the air the forecaster had in hand, not a measurement taken for the alert.

Skew-T log-p

Temperature in red, dew point in green, the mixed-layer parcel dashed.

Hodograph

The wind turning with height, colored by layer: ground to 1 km, 1 to 3 km, 3 to 6 km, 6 to 10 km.

Mixed-layer CAPE: 0 J/kg
Mixed-layer CIN: No buoyant parcel
Mixed-layer LCL: 604 m above ground
0-6 km bulk shear: 92 kt
0-1 km storm-relative helicity: 529 m²/s²
0-3 km storm-relative helicity: 564 m²/s²
Significant tornado parameter: 0.0
Supercell composite: -0.0

Open this sounding in Storm Lab

The text

As transmitted, in the capitals the NWS used until 2016.

575 
ACUS11 KWNS 240014
SWOMCD
SPC MCD 240013
MDZ000-VAZ000-DCZ000-240145-

MESOSCALE DISCUSSION 0264
NWS STORM PREDICTION CENTER NORMAN OK
0713 PM CDT WED MAR 23 2011

AREAS AFFECTED...SRN PA...NE WV...NRN VA

CONCERNING...SEVERE THUNDERSTORM WATCH 57...

VALID 240013Z - 240145Z

THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 57
CONTINUES.

SEVERE THREAT CONTINUES ACROSS MAINLY SE THIRD OF SEVERE
THUNDERSTORM WATCH 57. DOWNSTREAM OF WATCH...THREAT BECOMES MORE
MARGINAL AND AN ADDITIONAL WW IS NOT ANTICIPATED.

INITIAL TSTM ACTIVITY HAS MOVED OUT OF THE WATCH AREA...WHILE A
BROKEN LINE OF TSTMS HAS MOVED IN FROM THE WEST AND HAS CLEARED THE
NW HALF OF THE WATCH. 23Z OBJECTIVE ANALYSIS INDICATES ONLY MARGINAL
INSTABILITY /MU CAPE AOB 500 J/KG/ AHEAD OF THIS ACTIVITY.
HOWEVER...30-40 KTS OF EFFECTIVE SHEAR BE SUFFICIENT TO SUPPORT SOME
STORM ORGANIZATION...WITH STEEP MID-LEVEL LAPSE RATES CONTINUING TO
SUPPORT A THREAT OF MARGINALLY SEVERE HAIL. A LACK OF SFC-BASED
INSTABILITY WILL LIMIT THE OVERALL SEVERE WIND THREAT...WITH THE
GREATEST THREAT ACROSS THE SERN THIRD OF THE WATCH WHERE SFC TEMPS
ARE STILL CURRENTLY IN THE UPPER 50S/LOWER 60S.

DOWNSTREAM OF THE WATCH ACROSS SE PA...CNTRL MD...AND FAR NE
VA...STEEP LAPSE RATES WILL SUPPORT A MARGINAL THREAT OF SEVERE
HAIL...BUT THE OVERALL THREAT APPEARS TOO LOW FOR ANOTHER WW
ISSUANCE.

..DEAN.. 03/24/2011

...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT...

ATTN...WFO...AKQ...LWX...

LAT...LON   38437850 38667825 38897810 39107786 39297762 39427728
            39487697 39487687 39487674 39467646 39267635 39047640
            38627653 38287669 38127698 38067737 38057793 38007862
            38037892 38117908 38147902 38297883 38437850

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Mar 23, 8:39 PM EDT	Mesoscale Discussion	SPC	Alleghany, Amherst, Appomattox, Bath, Bedford, Bland and 37 more	66 min
Mar 23, 10:26 PM EDT	Mesoscale Discussion	SPC	Amelia, Brunswick, Charles City, Chesterfield, Dinwiddie, Gloucester and 31 more	64 min

Nearby

Mesoscale Discussions in Virginia, 2011 Mesoscale Discussions in Maryland, 2011 Every mesoscale discussion in 2011

Sources

The product and its follow-ups from the Iowa Environmental Mesonet's archive of National Weather Service and Storm Prediction Center text; the sounding from the Mesonet's radiosonde archive; radar from the NEXRAD Level II archive.