Alert archive / Virginia / Mesoscale Discussions in 2013
Mesoscale Discussion 1813
The Storm Prediction Center issued this mesoscale discussion at Aug 31, 2013, 11:55 AM EDT for 4 states. It was in force for 2 hr.
The area
The outline as issued.
The facts
- Issued
- Aug 31, 2013, 11:55 AM EDT (15:55 UTC)
- Expired
- Aug 31, 2013, 2:00 PM EDT
- In force
- 2 hr
- Issued by
- the Storm Prediction Center
- Chance of a watch
- 20%
All 38 counties
Breathitt County, KY, Floyd County, KY, Harlan County, KY, Knott County, KY, Letcher County, KY, Perry County, KY, Pike County, KY, Alleghany County, NC, Ashe County, NC, Avery County, NC, Caldwell County, NC, Madison County, NC, Mitchell County, NC, Watauga County, NC, Wilkes County, NC, Yancey County, NC, Carter County, TN, Cocke County, TN, Greene County, TN, Hancock County, TN, Hawkins County, TN, Johnson County, TN, Sullivan County, TN, Unicoi County, TN, Washington County, TN, Buchanan County, VA, City of Bristol, VA, City of Galax, VA, City of Norton, VA, Dickenson County, VA, Grayson County, VA, Lee County, VA, Russell County, VA, Scott County, VA, Smyth County, VA, Tazewell County, VA, Washington County, VA, Wise County, VA
The radar
The Knoxville radar (KMRX), 110 km from the middle of the area, began a volume at 15:55 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 12:00Z, 3.9 hours before the alert went out and 247 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.
- Mixed-layer CAPE
- 186 J/kg
- Mixed-layer CIN
- -75 J/kg
- Mixed-layer LCL
- 787 m above ground
- 0-6 km bulk shear
- 12 kt
- 0-1 km storm-relative helicity
- 2 m²/s²
- 0-3 km storm-relative helicity
- 33 m²/s²
- Significant tornado parameter
- 0.0
- Supercell composite
- 0.0
The text
As transmitted, in the capitals the NWS used until 2016.
032 ACUS11 KWNS 311556 SWOMCD SPC MCD 311555 NCZ000-VAZ000-WVZ000-TNZ000-KYZ000-311800- MESOSCALE DISCUSSION 1813 NWS STORM PREDICTION CENTER NORMAN OK 1055 AM CDT SAT AUG 31 2013 AREAS AFFECTED...PORTIONS SERN KY...SWRN VA...NERN TN...WRN NC. CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY VALID 311555Z - 311800Z PROBABILITY OF WATCH ISSUANCE...20 PERCENT SUMMARY...CLUSTER OF CONVECTION OVER ERN KY HAS GROWN SUFFICIENTLY UPSCALE TO ORGANIZE FORWARD-PROPAGATING OUTFLOW THAT MAY ENGENDER ADDITIONAL DEVELOPMENT ALONG ITS LEADING EDGE...IN TURN REINFORCING PRECIP LOADING TO DRIVE COLD POOL. GUSTS SHOULD REMAIN LARGELY SUB-SVR WITH RESPECT TO 50-KT SPEED CRITERIA...BUT STILL CAPABLE OF OCNL DAMAGE TO TREES/LIMBS AND WEAK STRUCTURES...ESPECIALLY ALONG NW-FACING SLOPES. DISCUSSION...VIS AND IR IMAGERY EACH INDICATE SMALL MIDLEVEL CYCLONIC CIRCULATION/VORTICITY MAX BEHIND THIS TSTM CLUSTER...MOVING SEWD OVER NERN KY ATTM...THAT MAY BE AIDING IN ASCENT AND SUBTLE STEEPENING OF WEAK AMBIENT LAPSE RATES ALOFT. FOREGOING AIR MASS FROM SERN KY INTO WRN NC SHOULD CONTINUE TO DESTABILIZE AMIDST STG SFC DIABATIC HEATING...AND FAVORABLE LOW-LEVEL MOISTURE AS REPRESENTED BY 70S F SFC DEW POINTS IN LOWER ELEVATIONS. RESULTANT MODIFICATIONS TO RAOBS AND FCST SOUNDINGS YIELDS 1500-2000 J/KG MLCAPE...AMIDST ONLY 20-25 KT EFFECTIVE SHEAR MAGNITUDE. LOW-MIDDLE LEVEL FLOW AND SHEAR EACH ARE RATHER WEAK ALREADY AND BECOME LESS WITH SEWD EXTENT ALONG PROJECTED PATH. MEAN-WIND VECTORS SHOULD REMAIN DIRECTED FROM NW AND NNW...ENCOURAGING SEWD NET TRANSLATION OF COLD POOL WITH SOME SSEWD PROPAGATION ALSO POSSIBLE. ..EDWARDS/GOSS.. 08/31/2013 ...PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT... ATTN...WFO...RNK...RLX...GSP...MRX...JKL... LAT...LON 37588347 37798263 36588066 35828163 35708313 37588347
Nearby
Mesoscale Discussions in Virginia, 2013Mesoscale Discussions in North Carolina, 2013Mesoscale Discussions in Tennessee, 2013Every mesoscale discussion in 2013
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.