Alert archive / Virginia / Mesoscale Discussions in 2012

Mesoscale Discussion 306

March 20, 201231 counties in North Carolina; 47 counties in Virginia; Monroe County, Pendleton County, West Virginia

The Storm Prediction Center issued this mesoscale discussion at Mar 20, 2012, 3:04 PM EDT for 31 counties in North Carolina; 47 counties in Virginia; Monroe County, Pendleton County, West Virginia. It was in force for 116 min.

The area

The outline as issued.

The facts

Issued
Mar 20, 2012, 3:04 PM EDT (19:04 UTC)
Expired
Mar 20, 2012, 5:00 PM EDT
In force
116 min
Issued by
the Storm Prediction Center
All 80 counties

Alamance County, NC, Alexander County, NC, Alleghany County, NC, Ashe County, NC, Avery County, NC, Burke County, NC, Cabarrus County, NC, Caldwell County, NC, Caswell County, NC, Catawba County, NC, Cleveland County, NC, Davidson County, NC, Davie County, NC, Forsyth County, NC, Gaston County, NC, Guilford County, NC, Iredell County, NC, Lincoln County, NC, McDowell County, NC, Mecklenburg County, NC, Person County, NC, Polk County, NC, Randolph County, NC, Rockingham County, NC, Rowan County, NC, Rutherford County, NC, Stokes County, NC, Surry County, NC, Watauga County, NC, Wilkes County, NC, Yadkin County, NC, Albemarle County, VA, Alleghany County, VA, Amherst County, VA, Appomattox County, VA, Augusta County, VA, Bath County, VA, Bedford County, VA, Botetourt County, VA, Buckingham County, VA, Campbell County, VA, Carroll County, VA, Charlotte County, VA, City of Buena Vista, VA, City of Charlottesville, VA, City of Covington, VA, City of Danville, VA, City of Galax, VA, City of Harrisonburg, VA, City of Lexington, VA, City of Lynchburg, VA, City of Martinsville, VA, City of Radford, VA, City of Roanoke, VA, City of Salem, VA, City of Staunton, VA, City of Waynesboro, VA, Craig County, VA, Floyd County, VA, Fluvanna County, VA, Franklin County, VA, Giles County, VA, Grayson County, VA, Greene County, VA, Halifax County, VA, Henry County, VA, Highland County, VA, Madison County, VA, Montgomery County, VA, Nelson County, VA, Page County, VA, Patrick County, VA, Pittsylvania County, VA, Pulaski County, VA, Roanoke County, VA, Rockbridge County, VA, Rockingham County, VA, Wythe County, VA, Monroe County, WV, Pendleton County, WV

The radar

The Roanoke radar (KFCX), 15 km from the middle of the area, began a volume at 19:05 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, 7.1 hours before the alert went out and 75 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, Roanoke, VA at 12:00Z on 2012-03-20Temperature and dew point through the depth of the atmosphere, with the mixed-layer parcel. CAPE 287 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, Roanoke, VA at 12:00Z on 2012-03-20The wind through the lowest 10 kilometers. Zero to 1 km storm-relative helicity 28 square meters per square second.1939Sfc1 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
287 J/kg
Mixed-layer CIN
-93 J/kg
Mixed-layer LCL
1105 m above ground
0-6 km bulk shear
16 kt
0-1 km storm-relative helicity
28 m²/s²
0-3 km storm-relative helicity
56 m²/s²
Significant tornado parameter
0.0
Supercell composite
0.3

Open this sounding in Storm Lab

The text

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

575 
ACUS11 KWNS 201905
SWOMCD
SPC MCD 201904
VAZ000-WVZ000-NCZ000-TNZ000-202100-

MESOSCALE DISCUSSION 0306
NWS STORM PREDICTION CENTER NORMAN OK
0204 PM CDT TUE MAR 20 2012

AREAS AFFECTED...WRN NC...CNTRL VA...FAR S-CNTRL WV

CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY

VALID 201904Z - 202100Z

THUNDERSTORMS WILL CONTINUE/INCREASE THROUGH EARLY EVENING.
MARGINALLY SEVERE HAIL AND GUSTY WINDS WILL BE THE MAIN THREAT.
BRIEF NATURE OF STRONG UPDRAFTS AND LACK OF ORGANIZATION WILL
PRECLUDE THE ISSUANCE OF A WW.

SCATTERED THUNDERSTORMS WERE DEVELOPING ALONG HIGHER TERRAIN FROM WV
SWD TO NC. TEMPERATURES HAVE WARMED INTO THE MID 70S TO LOW
80S...ERODING ANY INHIBITION AND RESULTING IN SBCAPE VALUES
APPROACHING 1000 J/KG. ADDITIONALLY...12Z REGIONAL RAOBS INDICATED
STEEP MIDLEVEL LAPSE RATES NEAR 7 DEG C/KM WHICH WILL AID IN
VIGOROUS THUNDERSTORM UPDRAFTS. HOWEVER...DEEP LAYER SHEAR REMAINS
VERY WEAK /BULK SHEAR LESS THAN 20 KT/ AND ANY STRONG THUNDERSTORM
ACTIVITY SHOULD BE SHORT-LIVED. FURTHER LIMITING ORGANIZATION AND
MAINTENANCE IS THE LACK OF UPPER LEVEL FORCING FOR ASCENT.
THEREFORE...SPORADIC EPISODES OF MARGINALLY SEVERE HAIL WILL BE
POSSIBLE BUT MORE LIKELY SMALL HAIL WILL BE MOST PREVALENT. LOCALLY
GUSTY WINDS AND HEAVY DOWNPOURS CAN ALSO BE EXPECTED. GIVEN LACK OF
ORGANIZATION AND PULSE-LIKE NATURE OF CONVECTION...A WW IS NOT
EXPECTED.

..LEITMAN.. 03/20/2012

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

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

LAT...LON   38807933 38647975 37928030 36858134 36298189 36088206
            35628238 35388235 35278218 35208181 35178135 35218081
            35398012 35837931 36597877 37727830 37937826 38437819
            38747845 38887902 38807933

Nearby

Mesoscale Discussions in Virginia, 2012Mesoscale Discussions in North Carolina, 2012Mesoscale Discussions in West Virginia, 2012Every mesoscale discussion in 2012

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.