Epic Outbreak of Tornadoes Across the Southeast on 27-28 April 2011 Impacts Northeast Georgia and Western North Carolina

Day 1 Convective Outlook issued at 0050 UTC 28 April 2011
SPC AC 280050
   
DAY 1 CONVECTIVE OUTLOOK  
NWS STORM PREDICTION CENTER NORMAN OK
0750 PM CDT WED APR 27 2011
   
VALID 280100Z - 281200Z
   
...THERE IS A HIGH RISK OF SVR TSTMS OVER ECNTRL/NERN AL...SERN TN
AND NWRN GA...
   
...THERE IS A MDT RISK OF SVR TSTMS FROM ERN KY SWD INTO CNTRL AL...
  
...THERE IS A SLGT RISK OF SVR TSTMS OVER MUCH OF THE ERN U.S. ASIDE
FROM NEW ENGLAND AND PENINSULAR FL...
   
...A HISTORICAL AND DANGEROUS OUTBREAK OF SEVERE THUNDERSTORM AND
TORNADOES CONTINUES ACROSS PARTS OF THE TN VALLEY AND SRN STATES...
   
CHANGES TO PREVIOUS OUTLOOK INCLUDE:
   
1/ EXTEND HIGH RISK TO INCLUDE MORE OF NWRN GA
2/ ADD HIGHER TORNADO PROBABILITIES IN MID-ATLANTIC
3/ REDUCE MDT RISK SWD FROM THE OH VLY
4/ TRIM WRN EDGE OF SVR RISKS IN TANDEM WITH FROPA
   
1. SVRL TORNADIC SUPERCELLS CONTINUE ENE FROM ECNTRL MS AND CNTRL AL
INTO ERN TN AT MID-EVENING.  FAVORED ZONE OF ADDITIONAL SUPERCELL
DEVELOPMENT MAY OCCUR ALONG LOW-LEVEL CONFLUENCE ACROSS SWRN-CNTRL
AL THROUGH LATE EVENING. THIS WILL BE AMID THE MOST VOLATILE
COMBINATION OF EFFECTIVE SRH AND INSTABILITY AND THERE WILL BE A
DANGEROUS STRONG-VIOLENT TORNADO RISK SPREADING ENE THROUGH
CNTRL/NERN AL INTO NWRN AL AND SERN TN THROUGH THE EVENING HOURS. 
AS A RESULT...THE HIGH RISK HAS BEEN EXPANDED EWD TO INCLUDE METRO
ATLANTA. PLEASE REFER TO LATEST MESOSCALE DISCUSSIONS /SWOMCD/ AND
WATCHES FOR UP-TO-THE-MINUTE METEOROLOGICAL DETAILS.
   
2.  A LEAD MID-LEVEL WAVE CONTINUES TO MOVE NEWD INTO THE
MID-ATLANTIC REGION.  INCREASING ASCENT...LOW-LEVEL CONFLUENCE ALONG
THE FOOTHILLS...MLCAPE TO 1500 J PER KG AND 300+ 0-1KM SRH GAVE RISE
TO SUPERCELLS WITH ISOLD TORNADOES EARLY THIS EVENING.  THERE WILL
BE A RISK OF BRIEF TORNADOES THROUGH MID-EVENING...ESPECIALLY FROM
CNTRL/NRN VA THROUGH DISTRICT OF COLUMBIA INTO CNTRL MD. 
OTHERWISE...DMGG WIND GUSTS AND LARGE HAIL WILL BE LIKELY...BEFORE
STORMS WEAKEN WITH LOSS OF INSOLATION.
   
3.  ALTHOUGH THERE WILL STILL BE A THREAT FOR ISOLD TORNADOES...DMGG
WINDS AND HAIL FROM THE OH RVR NWD TOWARD THE LOWER GREAT LAKES INTO
LATE EVENING...HIGHEST PROBABILITIES OF SUSTAINED SVR WEATHER WILL
REMAIN FROM KY COALFIELDS SWD.  CONSIDERABLE CLOUDS AND RAIN HAVE
MITIGATED STRONG DESTABILIZATION TODAY PER 00Z ILN SOUNDING. 
THEREFORE...MDT RISK/PROBABILITIES HAVE BEEN SHIFTED SWD.
   
..RACY.. 04/28/2011
   
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