Alert archive / North Carolina / Mesoscale Discussions in 2012

Mesoscale Discussion 1579

July 25, 20124 states

The Storm Prediction Center issued this mesoscale discussion at Jul 25, 2012, 2:32 AM EDT for 4 states. It was in force for 58 min.

The area

The outline as issued.

The facts

Issued: Jul 25, 2012, 2:32 AM EDT (06:32 UTC)
Expired: Jul 25, 2012, 3:30 AM EDT
In force: 58 min
Issued by: the Storm Prediction Center
Chance of a watch: 20%

All 31 counties

Letcher County, KY, Alexander County, NC, Ashe County, NC, Avery County, NC, Burke County, NC, Caldwell County, NC, Catawba County, NC, Cleveland County, NC, Gaston County, NC, Iredell County, NC, Lincoln County, NC, McDowell County, NC, Mecklenburg County, NC, Mitchell County, NC, Rutherford County, NC, Watauga County, NC, Wilkes County, NC, Yancey County, NC, Carter County, TN, Johnson County, TN, Sullivan County, TN, Unicoi County, TN, Washington County, TN, City of Bristol, VA, City of Norton, VA, Dickenson County, VA, Russell County, VA, Scott County, VA, Smyth County, VA, Washington County, VA, Wise County, VA

The radar

The Knoxville radar (KMRX), 129 km from the middle of the area, began a volume at 06:32 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

Greensboro/Hi Pt, NC (KGSO), launched 00:00Z, 6.5 hours before the alert went out and 187 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: 44 J/kg
Mixed-layer CIN: -486 J/kg
Mixed-layer LCL: 1440 m above ground
0-6 km bulk shear: 28 kt
0-1 km storm-relative helicity: 179 m²/s²
0-3 km storm-relative helicity: 217 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.

537 
ACUS11 KWNS 250632
SWOMCD
SPC MCD 250632 
NCZ000-SCZ000-VAZ000-TNZ000-KYZ000-250730-

MESOSCALE DISCUSSION 1579
NWS STORM PREDICTION CENTER NORMAN OK
0132 AM CDT WED JUL 25 2012

AREAS AFFECTED...EXTREME SWRN VA/EXTREME NERN TN/PARTS OF WRN NC

CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY 

VALID 250632Z - 250730Z

PROBABILITY OF WATCH ISSUANCE...20 PERCENT

SUMMARY...A SMALL MCS THAT FORMED OVER EXTREME SERN KY INTO EXTREME
SWRN VA HAS PRODUCED A COLD POOL AIDING IN AN INCREASE IN SEWD
MOVEMENT /NEAR 40 KT/.  LOCALLY STRONG WIND GUSTS WILL BE POSSIBLE
AS THIS ACTIVITY TRACKS SEWD THROUGH EXTREME SWRN VA/EXTREME NERN TN
INTO WRN NC DURING THE NEXT FEW HOURS /UNTIL 08-09Z/.  GIVEN
SPATIOTEMPORAL LIMITATIONS...A WW IS UNLIKELY AT THIS TIME.  AS
STORMS CONTINUE TO FORM OVER ERN KY WITH A TENDENCY TO TRAIN
SEWD...RAINFALL RATES OF 1.5-2 INCH PER HOUR ARE LIKELY...GIVEN A
RICHLY MOIST AIR MASS.

DISCUSSION...TRENDS IN REGIONAL RADAR IMAGERY INDICATED A SMALL MCS
THAT FORMED OVER EXTREME ERN/SERN KY INTO EXTREME SWRN VA BETWEEN
04-0530Z/ HAD PRODUCED HEAVY RAINFALL RATES /1-2+ IN/HR AS INDICATED
BY RADAR ESTIMATES AND NESDIS SATELLITE ESTIMATES FOR BUCHANAN
COUNTY VA/.  ADDITIONAL STORMS HAVE BEGUN TO DEVELOP NWWD ACROSS ERN
KY...WITH ALL OF THESE STORMS BEING FED BY W/NWLY LOW LEVEL WINDS
PROVIDING AN INFLUX OF RESIDUAL MODERATE INSTABILITY RESIDING ACROSS
KY AND MIDDLE/ERN TN.  35 KT NWLY MIDLEVEL WINDS ARE CONTRIBUTING TO
SUFFICIENT EFFECTIVE BULK SHEAR FOR SOME ORGANIZATION AND SEWD
MOVEMENT AS OBSERVED IN THE SWRN VA TSTM CLUSTER.

THE DOWNSTREAM AIR MASS ACROSS WRN NC IS LESS UNSTABLE GIVEN TIME OF
DAY AND EARLIER CONVECTIVE OVERTURNING.  THE LAST FEW RUNS OF THE
HRRR SUGGEST THE ERN KY/SWRN VA STORMS WILL TRACK SEWD...BUT WEAKEN
AS THEY REACH AREAS OF GREATER DOWNSTREAM STABILIZATION.

..PETERS/THOMPSON.. 07/25/2012

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

ATTN...WFO...RNK...RLX...CAE...GSP...MRX...JKL...

LAT...LON   37138161 35738063 35018077 35258202 35688234 36438273
            36658288 37238315 37138161

SPC that day

Everything else SPC issued on the same UTC day.

Issued	Product	Office	Counties	Lasted
Jul 24, 8:59 PM EDT	Mesoscale Discussion	SPC	Adair, Anderson, Barren, Bourbon, Boyle, Breckinridge and 52 more	91 min
Jul 25, 4:48 PM EDT	Mesoscale Discussion	SPC	Anderson, Bath, Boone, Bourbon, Boyd, Boyle and 58 more	117 min
Jul 25, 3:11 PM EDT	Mesoscale Discussion	SPC	Alexander, Alleghany, Ashe, Avery, Buncombe, Burke and 30 more	3 hr

Nearby

Mesoscale Discussions in North Carolina, 2012 Mesoscale Discussions in Virginia, 2012 Mesoscale Discussions in Tennessee, 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.