Alert archive / Virginia / Mesoscale Discussions in 2011

Mesoscale Discussion 1321

June 20, 2011Alamance County, Caswell County, Orange County, North Carolina; 12 counties in Virginia; Greenbrier County, Monroe County, Nicholas County, West Virginia

The Storm Prediction Center issued this mesoscale discussion at Jun 20, 2011, 2:36 PM EDT for Alamance County, Caswell County, Orange County, North Carolina; 12 counties in Virginia; Greenbrier County, Monroe County, Nicholas County, West Virginia. It was in force for 54 min.

The area

The outline as issued.

The facts

Issued: Jun 20, 2011, 2:36 PM EDT (18:36 UTC)
Expired: Jun 20, 2011, 3:30 PM EDT
In force: 54 min
Issued by: the Storm Prediction Center

Counties Alamance County, NC, Caswell County, NC, Orange County, NC, Alleghany County, VA, Bedford County, VA, Botetourt County, VA, City of Covington, VA, City of Danville, VA, City of Martinsville, VA, City of Roanoke, VA, City of Salem, VA, Craig County, VA, Franklin County, VA, Pittsylvania County, VA, Roanoke County, VA, Greenbrier County, WV, Monroe County, WV, Nicholas County, WV

The radar

The Roanoke radar (KFCX), 42 km from the middle of the area, began a volume at 18:36 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 12:00Z, 6.6 hours before the alert went out and 45 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: 20 J/kg
Mixed-layer CIN: -183 J/kg
Mixed-layer LCL: 724 m above ground
0-6 km bulk shear: 22 kt
0-1 km storm-relative helicity: 148 m²/s²
0-3 km storm-relative helicity: 210 m²/s²
Significant tornado parameter: 0.0
Supercell composite: 0.4

Open this sounding in Storm Lab

The text

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

698 
ACUS11 KWNS 201837
SWOMCD
SPC MCD 201836
VAZ000-NCZ000-WVZ000-201930-

MESOSCALE DISCUSSION 1321
NWS STORM PREDICTION CENTER NORMAN OK
0136 PM CDT MON JUN 20 2011

AREAS AFFECTED...ERN WV...WRN VA...N CNTRL NC

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE

VALID 201836Z - 201930Z

ISOLATED HAIL AND DMGG WINDS WILL BE POSSIBLE THIS AFTERNOON. SHOULD
COVERAGE APPEAR MORE THAN ISOLATED...A WW MAY BE CONSIDERED.

CONVECTIVE DEBRIS FROM AN EARLIER MCS HAS GENERALLY LIMITED
DESTABILIZATION ACROSS THE REGION. HOWEVER...EAST OF THE THICKER
CLOUD COVER...PATCHES OF CLEARING HAVE LED TO A NARROW CORRIDOR OF
STRONGER DIURNAL HEATING...WHERE MESOANALYSIS INDICATES 1000-1500
J/KG MLCAPE. ALTHOUGH MID LEVEL LAPSE RATES REMAIN MARGINAL AT THE
MOMENT...WNWLY FLOW ALONG THE BACKSIDE OF AN EXITING SHORT WAVE
TROUGH WILL ADVECT MORE FAVORABLE LAPSE RATES THROUGH THE
AFTERNOON...WHILE LOW LEVEL LAPSE RATES WILL CONTINUE TO STEEPEN
AMIDST STRONG SURFACE HEATING AS WELL. AS A RESULT...MODEST WNWLY
DEEP LAYER SHEAR AND FURTHER DESTABILIZATION COULD SUPPORT
MULTICELLULAR CLUSTERS AND BRIEFLY ROTATING STORMS CAPABLE OF DMGG
WINDS AND HAIL. INITIAL DEVELOPMENT APPEARS TO BE OCCURRING ON A
REMNANT NNW-SSE ORIENTED OUTFLOW BOUNDARY...CENTERED ROUGHLY OVER
ROA. HOWEVER...PER 1830Z WV IMAGERY...LARGE SCALE UPPER RIDGING IS
DEVELOPING EWD INTO THE REGION...AND MAY SUPPRESS MORE WIDESPREAD
COVERAGE OF SEVERE STORMS. TRENDS WILL CONTINUE TO BE MONITORED.

..HURLBUT.. 06/20/2011

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

ATTN...WFO...RAH...RNK...RLX...

LAT...LON   35727934 36898007 37818095 38308082 37997985 36767914
            35967909 35727934

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Jun 19, 9:07 PM EDT	Mesoscale Discussion	SPC	Cherokee, Clay, Graham, Haywood, Jackson, Macon and 1 more	53 min
Jun 19, 9:41 PM EDT	Severe Thunderstorm Watch	SPC	Buncombe, Cherokee, Clay, Graham, Haywood, Henderson and 5 more	5 hr
Jun 20, 9:53 AM EDT	Mesoscale Discussion	SPC	Madison, Mitchell, Yancey	97 min
Jun 20, 12:46 PM EDT	Mesoscale Discussion	SPC	Alexander, Ashe, Avery, Burke, Caldwell, Mitchell and 2 more	59 min

Nearby

Mesoscale Discussions in Virginia, 2011 Mesoscale Discussions in North Carolina, 2011 Mesoscale Discussions in West Virginia, 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.