Alert archive / Virginia / Mesoscale Discussions in 2011

Mesoscale Discussion 895

May 23, 20115 states

The Storm Prediction Center issued this mesoscale discussion at May 23, 2011, 2:33 PM EDT for 5 states. It was in force for 87 min.

The area

The outline as issued.

The facts

Issued
May 23, 2011, 2:33 PM EDT (18:33 UTC)
Expired
May 23, 2011, 4:00 PM EDT
In force
87 min
Issued by
the Storm Prediction Center
All 117 counties

Allegany County, MD, Carroll County, MD, Charles County, MD, Frederick County, MD, Howard County, MD, Montgomery County, MD, Washington County, MD, Alamance County, NC, Caswell County, NC, Chatham County, NC, Davidson County, NC, Durham County, NC, Forsyth County, NC, Franklin County, NC, Granville County, NC, Guilford County, NC, Orange County, NC, Person County, NC, Rockingham County, NC, Stokes County, NC, Vance County, NC, Warren County, NC, Adams County, PA, Bedford County, PA, Blair County, PA, Cambria County, PA, Centre County, PA, Clearfield County, PA, Clinton County, PA, Cumberland County, PA, Dauphin County, PA, Franklin County, PA, Fulton County, PA, Huntingdon County, PA, Juniata County, PA, Lycoming County, PA, Mifflin County, PA, Perry County, PA, Snyder County, PA, Union County, PA, Albemarle County, VA, Amelia County, VA, Amherst County, VA, Appomattox County, VA, Arlington County, VA, Augusta County, VA, Bedford County, VA, Botetourt County, VA, Brunswick County, VA, Buckingham County, VA, Campbell County, VA, Caroline County, VA, Charlotte County, VA, Chesterfield County, VA, City of Alexandria, VA, City of Buena Vista, VA, City of Charlottesville, VA, City of Colonial Heights, VA, City of Danville, VA, City of Fairfax, VA, City of Falls Church, VA, City of Fredericksburg, VA, City of Harrisonburg, VA, City of Lexington, VA, City of Lynchburg, VA, City of Manassas, VA, City of Manassas Park, VA, City of Martinsville, VA, City of Richmond, VA, City of Roanoke, VA, City of Staunton, VA, City of Waynesboro, VA, City of Winchester, VA, Clarke County, VA, Culpeper County, VA, Cumberland County, VA, Dinwiddie County, VA, Fairfax County, VA, Fauquier County, VA, Fluvanna County, VA, Franklin County, VA, Frederick County, VA, Goochland County, VA, Greene County, VA, Halifax County, VA, Hanover County, VA, Henry County, VA, Highland County, VA, King George County, VA, Loudoun County, VA, Louisa County, VA, Lunenburg County, VA, Madison County, VA, Mecklenburg County, VA, Nelson County, VA, Nottoway County, VA, Orange County, VA, Page County, VA, Pittsylvania County, VA, Powhatan County, VA, Prince Edward County, VA, Prince William County, VA, Rappahannock County, VA, Rockbridge County, VA, Rockingham County, VA, Shenandoah County, VA, Spotsylvania County, VA, Stafford County, VA, Warren County, VA, Berkeley County, WV, Grant County, WV, Hampshire County, WV, Hardy County, WV, Jefferson County, WV, Mineral County, WV, Morgan County, WV, Pendleton County, WV

The radar

The Sterling radar (KLWX), 95 km from the middle of the area, began a volume at 18:35 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 watches that followed

Watches SPC issued over any of the same counties within four hours of this discussion.

The nearest sounding before it

Washington/Dulle, VA (KIAD), launched 12:00Z, 6.6 hours before the alert went out and 101 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-pSkew-T log-p diagram, Washington/Dulle, VA at 12:00Z on 2011-05-23Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 22 joules per kilogram.LCLLFCEL10008507005003002001001 km2 km3 km6 km9 km12 km15 km-30°-20°-10°0°10°20°30°40°
Temperature in red, dew point in green, the mixed-layer parcel dashed.
HodographHodograph, Washington/Dulle, VA at 12:00Z on 2011-05-23The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 152 square meters per square second.193958Sfc1 km3 km6 km9 kmRMLM
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
22 J/kg
Mixed-layer CIN
-131 J/kg
Mixed-layer LCL
581 m above ground
0-6 km bulk shear
32 kt
0-1 km storm-relative helicity
152 m²/s²
0-3 km storm-relative helicity
177 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.

171 
ACUS11 KWNS 231833
SWOMCD
SPC MCD 231833 
PAZ000-MDZ000-VAZ000-DCZ000-NCZ000-WVZ000-232000-

MESOSCALE DISCUSSION 0895
NWS STORM PREDICTION CENTER NORMAN OK
0133 PM CDT MON MAY 23 2011

AREAS AFFECTED...CNTRL PA/VA/NC...WRN/CNTRL MD...ERN WV PANHANDLE

CONCERNING...SEVERE THUNDERSTORM WATCH 338...

VALID 231833Z - 232000Z

THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 338
CONTINUES.

SCATTERED TSTMS WILL LIKELY DEVELOP ALONG THE APPALACHIANS FROM PA
TO NC IN THE NEXT FEW HOURS. A WW ISSUANCE TO THE S OF WW 338 WILL
BE LIKELY BY 20Z.

ALTHOUGH AN INITIAL BAND OF TSTMS HAD WEAKENED ACROSS CNTRL PA...A
RECENT INCREASE IN SHOWER ACTIVITY HAS OCCURRED ACROSS WRN PA INTO
ERN WV IN A LOBE OF FORCED ASCENT ASSOCIATED WITH AN REMNANT MCV
CENTERED OVER NWRN PA. RECENT HRRR RUNS REMAIN ADAMANT IN THIS
ACTIVITY INCREASING IN INTENSITY DURING THE AFTERNOON AS IT DEVELOPS
EWD INTO WW 338. CONTINUED HEATING DOWNSTREAM INTO AND THROUGH THE
80S WILL RESULT IN A LARGELY UNCAPPED ENVIRONMENT BASED ON A
MODIFIED 16Z IAD RAOB. WITH 50 KT W/SWLYS AT 4 KM AGL SAMPLED IN
FCX/LWX VWP DATA...SUPERCELL STRUCTURES AND ORGANIZED LINE SEGMENTS
WILL BE FAVORABLE FOR SEVERE HAIL/WIND.

WITH GREATER BUOYANCY AND INCREASINGLY AGITATED CU NOTED IN VISIBLE
SATELLITE IMAGERY INTO NWRN NC AHEAD OF A SMALL MCV IN SWRN VA...A
DAMAGING WIND/HAIL THREAT WILL ALSO EXIST TO THE S OF WW 338.
ALTHOUGH LOW-LEVEL SHEAR SHOULD REMAIN MODEST...THE MODERATE TO
STRONGLY UNSTABLE AIR MASS ALONG WITH A POTENTIALLY MORE DISCRETE
MODE COULD FAVOR AN ISOLATED TORNADO THREAT IN PORTIONS OF SRN
VA/NRN NC.

..GRAMS.. 05/23/2011

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

ATTN...WFO...AKQ...CTP...LWX...RAH...RNK...PBZ...RLX...GSP...

LAT...LON   40677871 41257845 41517807 41427710 41087671 39017687
            37627723 36477769 35957838 35667924 35818040 36058050
            36648023 40677871

SPC that day

Everything else SPC issued on the same UTC day.

IssuedProductOfficeCountiesLasted
May 23, 10:33 AM EDTMesoscale DiscussionSPCAllegany, Baltimore, Carroll, Frederick, Garrett, Howard and 4 more87 min
May 23, 10:48 AM EDTSevere Thunderstorm WatchSPCAllegany, Anne Arundel, Baltimore, Calvert, Carroll, Charles and 8 more9 hr
May 23, 4:40 PM EDTMesoscale DiscussionSPCAnne Arundel, Baltimore, Calvert, Carroll, Cecil, Charles and 9 more95 min
May 22, 9:02 PM EDTMesoscale DiscussionSPCAlexander, Alleghany, Catawba, Surry, Wilkes, Yadkin58 min
May 23, 3:16 PM EDTSevere Thunderstorm WatchSPCAlamance, Alexander, Alleghany, Ashe, Avery, Bertie and 41 more7 hr
May 23, 7:02 PM EDTMesoscale DiscussionSPCAlamance, Caswell, Chatham, Davidson, Davie, Durham and 17 more58 min
May 23, 8:25 AM EDTMesoscale DiscussionSPCCrawford, Erie65 min
May 23, 7:20 PM EDTMesoscale DiscussionSPCBoone, Brooke, Cabell, Calhoun, Doddridge, Jackson and 16 more85 min

Nearby

Mesoscale Discussions in Virginia, 2011Mesoscale Discussions in Pennsylvania, 2011Mesoscale Discussions in North Carolina, 2011Every 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.