Alert archive / South Carolina / Mesoscale Discussions in 2012

Mesoscale Discussion 606

April 27, 20126 counties in Georgia; 25 counties in South Carolina

The Storm Prediction Center issued this mesoscale discussion at Apr 27, 2012, 2:42 PM EDT for 6 counties in Georgia; 25 counties in South Carolina. It was in force for 2 hr.

The area

The outline as issued.

The facts

Issued: Apr 27, 2012, 2:42 PM EDT (18:42 UTC)
Expired: Apr 27, 2012, 4:45 PM EDT
In force: 2 hr
Issued by: the Storm Prediction Center

All 31 counties

Columbia County, GA, Elbert County, GA, Hart County, GA, Lincoln County, GA, Richmond County, GA, Wilkes County, GA, Abbeville County, SC, Aiken County, SC, Anderson County, SC, Barnwell County, SC, Calhoun County, SC, Chester County, SC, Edgefield County, SC, Fairfield County, SC, Greenville County, SC, Greenwood County, SC, Kershaw County, SC, Lancaster County, SC, Laurens County, SC, Lee County, SC, Lexington County, SC, McCormick County, SC, Newberry County, SC, Oconee County, SC, Orangeburg County, SC, Pickens County, SC, Richland County, SC, Saluda County, SC, Spartanburg County, SC, Sumter County, SC, Union County, SC

The radar

The Columbia radar (KCAE), 61 km from the middle of the area, began a volume at 18:44 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.

Severe Thunderstorm Watch 195Apr 27, 5:35 PM EDT

The nearest sounding before it

Charleston AFB, SC (KCHS), launched 12:00Z, 6.7 hours before the alert went out and 213 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: 75 J/kg
Mixed-layer CIN: -239 J/kg
Mixed-layer LCL: 1255 m above ground
0-6 km bulk shear: 33 kt
0-1 km storm-relative helicity: 120 m²/s²
0-3 km storm-relative helicity: 179 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.

234 
ACUS11 KWNS 271842
SWOMCD
SPC MCD 271842 
SCZ000-NCZ000-GAZ000-272045-

MESOSCALE DISCUSSION 0606
NWS STORM PREDICTION CENTER NORMAN OK
0142 PM CDT FRI APR 27 2012

AREAS AFFECTED...FAR NERN GA...WRN AND CNTRL SC

CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE 

VALID 271842Z - 272045Z

A THREAT FOR SEVERE HAIL AND WIND GUSTS IS EXPECTED TO DEVELOP LATE
THIS AFTERNOON INTO THIS EVENING AND A WW MAY BE NEEDED.

CURRENT RADAR IMAGERY SHOWS A WEAK BAND OF CONVECTION ACROSS NERN GA
MOVING EWD INTO WRN SC. THESE SHOWERS APPEAR TO BE DEVELOPING ALONG
A WEAK VORTICITY MAXIMUM ASSOCIATED WITH A SUBTLE PERTURBATION IN
THE WLY FLOW ALOFT. MOSTLY CLEAR SKIES AND MOISTURE ADVECTION AHEAD
OF THIS BAND WILL ALLOW FOR AMPLE DESTABILIZATION ACROSS PORTIONS OF
FAR ERN GA AND WRN/CNTRL SC. LATEST SURFACE OBJECTIVE ANALYSIS
INDICATES SBCAPE VALUES ALREADY IN EXCESS OF 1000 J/KG. INCREASED
SFC HEATING AND STEEP LOW-LEVEL LAPSE RATES WILL LIKELY RESULT IN
SBCAPE VALUES AOA 2000 J/KG LATER THIS AFTERNOON.
ADDITIONALLY...EFFECTIVE SHEAR VALUES ARE HIGH ENOUGH /30 TO 40 KTS/
FOR SOME UPDRAFT ORGANIZATION. CONSEQUENTLY...A MULTICELL CLUSTER
CAPABLE OF PRODUCING SEVERE HAIL AND...GIVEN THE STEEP LOW-LEVEL
LAPSE RATES AND RESULTANT DCAPE VALUES AOA 900 J/KG...DAMAGING WINDS
IS POSSIBLE. TRENDS WILL CONTINUE TO BE MONITORED FOR A POSSIBLE WW.

..MOSIER.. 04/27/2012

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

ATTN...WFO...ILM...CHS...CAE...GSP...FFC...

LAT...LON   33148152 33338225 33618264 33878295 33978311 34158317
            34638316 35048296 35108251 35068195 34978124 34818061
            34758040 34398002 33968011 33578027 33318085 33148152

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Apr 27, 11:34 AM EDT	Mesoscale Discussion	SPC	Barrow, Clarke, Columbia, Elbert, Glascock, Greene and 12 more	56 min
Apr 27, 5:36 PM EDT	Severe Thunderstorm Watch	SPC	Columbia, Elbert, Franklin, Hart, Lincoln, McDuffie and 2 more	6 hr

Nearby

Mesoscale Discussions in South Carolina, 2012 Mesoscale Discussions in Georgia, 2012 Every 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.