Alert archive / Virginia / Mesoscale Discussions in 2004

Mesoscale Discussion 809

May 21, 20048 counties in North Carolina; 65 counties in Virginia; 5 counties in West Virginia

The Storm Prediction Center issued this mesoscale discussion at May 21, 2004, 9:34 PM EDT for 8 counties in North Carolina; 65 counties in Virginia; 5 counties in West Virginia. It was in force for 86 min.

The area

The outline as issued.

The facts

Issued: May 21, 2004, 9:34 PM EDT (01:34 UTC)
Expired: May 21, 2004, 11:00 PM EDT
In force: 86 min
Issued by: the Storm Prediction Center

All 78 counties

Caswell County, NC, Person County, NC, Rockingham County, NC, Stokes County, NC, Surry County, NC, Vance County, NC, Warren County, NC, Yadkin County, NC, Albemarle County, VA, Alleghany County, VA, Amelia County, VA, Amherst County, VA, Appomattox County, VA, Augusta County, VA, Bath County, VA, Bedford County, VA, Bland County, VA, Botetourt County, VA, Brunswick County, VA, Buckingham County, VA, Campbell County, VA, Carroll County, VA, Charlotte County, VA, Chesterfield County, VA, City of Buena Vista, VA, City of Charlottesville, VA, City of Colonial Heights, VA, City of Covington, VA, City of Danville, VA, City of Emporia, VA, City of Galax, VA, City of Hopewell, VA, City of Lexington, VA, City of Lynchburg, VA, City of Martinsville, VA, City of Petersburg, VA, City of Radford, VA, City of Richmond, VA, City of Roanoke, VA, City of Salem, VA, City of Staunton, VA, City of Waynesboro, VA, Craig County, VA, Cumberland County, VA, Dinwiddie County, VA, Floyd County, VA, Fluvanna County, VA, Franklin County, VA, Giles County, VA, Goochland County, VA, Greene County, VA, Greensville County, VA, Halifax County, VA, Hanover County, VA, Henrico County, VA, Henry County, VA, Louisa County, VA, Lunenburg County, VA, Madison County, VA, Mecklenburg County, VA, Montgomery County, VA, Nelson County, VA, Nottoway County, VA, Orange County, VA, Patrick County, VA, Pittsylvania County, VA, Powhatan County, VA, Prince Edward County, VA, Prince George County, VA, Pulaski County, VA, Roanoke County, VA, Rockbridge County, VA, Spotsylvania County, VA, Greenbrier County, WV, Mercer County, WV, Monroe County, WV, Raleigh County, WV, Summers County, WV

The radar

The Roanoke radar (KFCX), 102 km from the middle of the area, began a volume at 01:34 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

Roanoke, VA (KRNK), launched 00:00Z, 1.6 hours before the alert went out and 39 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: 1456 J/kg
Mixed-layer CIN: -2 J/kg
Mixed-layer LCL: 1526 m above ground
0-6 km bulk shear: 14 kt
0-1 km storm-relative helicity: 16 m²/s²
0-3 km storm-relative helicity: -12 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.

155 
ACUS11 KWNS 220134
SWOMCD
SPC MCD 220134 
VAZ000-NCZ000-WVZ000-220300-

MESOSCALE DISCUSSION 0809
NWS STORM PREDICTION CENTER NORMAN OK
0834 PM CDT FRI MAY 21 2004

AREAS AFFECTED...SRN WV...VA AND NRN NC

CONCERNING...SEVERE THUNDERSTORM POTENTIAL 

VALID 220134Z - 220300Z

A LARGE-SCALE BOW ECHO IS CURRENTLY MOVING SWD AND SHOULD AFFECT VA
AND SRN WV OVER THE NEXT FEW HOURS. A MARGINAL SEVERE POTENTIAL WILL
EXIST WITH THE LINE WITH THE MAIN THREAT BEING WIND DAMAGE.

THE AIRMASS AHEAD OF THE CONVECTIVE LINE IS MODERATELY UNSTABLE AND
THE LINE COULD CONTINUE SWD INTO VA LATE THIS EVENING. THE 00Z
SOUNDING FROM IAD SHOWS 0-6 KM SHEAR AROUND 15 KT AND THIS MAY BE
PROBLEMATIC CONCERNING STORM ORGANIZATION. AS THE LINE MOVES INTO
THIS WEAKER SHEAR ENVIRONMENT...THE WEAKENING TREND SHOULD CONTINUE
AND THE SEVERE THREAT SHOULD BECOME MARGINAL. ISOLATED WIND DAMAGE
WOULD BE THE PRIMARY THREAT IF THE STORMS CAN REMAIN ABOVE SEVERE
LIMITS.

..BROYLES.. 05/22/2004

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

ATTN...WFO...AKQ...LWX...RAH...RNK...RLX...

37838139 38397929 38467765 37507712 36417744 36118076

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
May 22, 2:25 AM EDT	Mesoscale Discussion	SPC	Brooke, Hancock, Marshall, Ohio	2 hr

Nearby

Mesoscale Discussions in Virginia, 2004 Mesoscale Discussions in North Carolina, 2004 Mesoscale Discussions in West Virginia, 2004 Every mesoscale discussion in 2004

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.