Alert archive / Virginia / Mesoscale Discussions in 2011

Mesoscale Discussion 174

February 28, 2011Sussex County, Delaware; 8 counties in Maryland; 26 counties in Virginia

The Storm Prediction Center issued this mesoscale discussion at Feb 28, 2011, 12:49 PM EST for Sussex County, Delaware; 8 counties in Maryland; 26 counties in Virginia. It was in force for 56 min.

The area

The outline as issued.

The facts

Issued: Feb 28, 2011, 12:49 PM EST (17:49 UTC)
Expired: Feb 28, 2011, 1:45 PM EST
In force: 56 min
Issued by: the Storm Prediction Center

All 35 counties

Sussex County, DE, Calvert County, MD, Caroline County, MD, Charles County, MD, Dorchester County, MD, Saint Mary's County, MD, Somerset County, MD, Talbot County, MD, Wicomico County, MD, Appomattox County, VA, Bedford County, VA, Buckingham County, VA, Campbell County, VA, Caroline County, VA, Carroll County, VA, City of Fredericksburg, VA, City of Galax, VA, City of Lynchburg, VA, City of Martinsville, VA, Cumberland County, VA, Essex County, VA, Fluvanna County, VA, Franklin County, VA, Goochland County, VA, Henry County, VA, King George County, VA, Louisa County, VA, Northumberland County, VA, Patrick County, VA, Pittsylvania County, VA, Prince Edward County, VA, Richmond County, VA, Spotsylvania County, VA, Stafford County, VA, Westmoreland County, VA

The radar

The Norfolk radar (KAKQ), 112 km from the middle of the area, began a volume at 17:50 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 12:00Z, 5.8 hours before the alert went out and 147 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: 525 m above ground
0-6 km bulk shear: 76 kt
0-1 km storm-relative helicity: 705 m²/s²
0-3 km storm-relative helicity: 770 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.1

Open this sounding in Storm Lab

The text

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

242 
ACUS11 KWNS 281750
SWOMCD
SPC MCD 281749
DEZ000-MDZ000-VAZ000-281845-

MESOSCALE DISCUSSION 0174
NWS STORM PREDICTION CENTER NORMAN OK
1149 AM CST MON FEB 28 2011

AREAS AFFECTED...CNTRL VA / EASTERN SHORE

CONCERNING...TORNADO WATCH 32...

VALID 281749Z - 281845Z

THE SEVERE WEATHER THREAT FOR TORNADO WATCH 32 CONTINUES.

SEVERE THREAT CONTINUES TO EXIST ACROSS THE ERN PORTIONS OF TORNADO
WATCH 32.  DMGG WINDS APPEAR TO BE THE PRIMARY THREAT.

REGIONAL RADAR MOSAIC SHOWS A CONVECTIVE LINE ELONGATED FROM NEAR
D.C. SWWD TO ROA WITH LITTLE IN THE WAY OF LIGHTNING BEING OBSERVED
OVER THE PAST HOUR.  RECENT SURFACE ANALYSIS PLACES A COLD FRONT
WELL W OF THE CONVECTIVE LINE IN WV AND KY.  THE SW-NE ORIENTATION
OF THE COLD POOL IS LARGELY PARALLEL TO MEAN DEEP LAYER FLOW...AND
LESS SUPPORTIVE OF SUSTAINED DEEPER LOW LEVEL CONVERGENCE AS LOW
LEVEL WINDS HAVE VEERED TO SWLY.  AHEAD OF THE LINE...BROKEN HIGH
LEVEL CLOUD COVER HAS ALLOWED TEMPS TO RISE INTO THE 70S WITH
LOWER-MID 50S DEWPOINTS IN PLACE RESULTING IN WEAK CONVECTIVE
INSTABILITY.  ALTHOUGH THE PRIMARY MID-LEVEL TROUGH IS OVER THE MS
VALLEY MOVING INTO THE TN VALLEY REGION...SUFFICIENT SURFACE HEATING
LEADING TO STEEPENING LOW LEVEL LAPSE RATES MAY LEAD TO AN INCREASE
IN CONVECTIVE LINE INTENSITY ACROSS THE EASTERN SHORE DURING THE
NEXT HOUR OR SO.

..SMITH.. 02/28/2011

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

ATTN...WFO...PHI...AKQ...LWX...RNK...

LAT...LON   36628102 37527908 38917670 38887546 38497501 37837598
            37767776 36587923 36628102

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Feb 28, 8:36 AM EST	Mesoscale Discussion	SPC	Allegany, Carroll, Frederick, Garrett, Howard, Montgomery and 1 more	24 min
Feb 28, 8:57 AM EST	Tornado Watch	SPC	Allegany, Calvert, Carroll, Charles, Frederick, Howard and 4 more	9 hr
Feb 28, 5:47 AM EST	Tornado Watch	SPC	Buchanan, Dickenson, Lee, Russell, Scott, Washington and 3 more	5 hr
Feb 28, 6:59 AM EST	Tornado Watch	SPC	Lee, Russell, Scott, Washington, Wise, City of Bristol and 1 more	7 hr
Feb 28, 12:25 PM EST	Mesoscale Discussion	SPC	Russell, Scott, Washington, City of Bristol	95 min
Feb 28, 4:36 PM EST	Mesoscale Discussion	SPC	City of Danville	84 min

Nearby

Mesoscale Discussions in Virginia, 2011 Mesoscale Discussions in Maryland, 2011 Mesoscale Discussions in Delaware, 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.