Apr 10, 2009 2000 UTC Day 1 Convective Outlook
Updated: Fri Apr 10 18:48:23 UTC 2009
Probabilistic to Categorical Outlook Conversion Table (Effective Feb 14, 2006).
Public Severe Weather Outlook

The SPC is forecasting ...severe thunderstorms expected over parts of the tennessee valley and southern appalachians this afternoon and tonight....   Please read the latest public statement about this event.

Categorical Graphic
20090410 2000 UTC Day 1 Outlook Graphic
Probabilistic Tornado Graphic
20090410 2000 UTC Day 1 Tornado Probabilities Graphic
Torndao Legend Image
Probabilistic Damaging Wind Graphic
20090410 2000 UTC Day 1 Damaging Wind Probabilities Graphic
Wind Legend Image
Probabilistic Large Hail Graphic
20090410 2000 UTC Day 1 Large Hail Probabilities Graphic
Hail Legend Image
   SPC AC 101844
   
   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0144 PM CDT FRI APR 10 2009
   
   VALID 102000Z - 111200Z
   
   ...THERE IS A HIGH RISK OF SVR TSTMS THIS AFTERNOON INTO EVENING
   OVER NERN AL...SERN TN AND NWRN GA...
   
   ...THERE IS A MDT RISK OF SVR TSTMS THIS AFTERNOON INTO TONIGHT OVER
   PARTS OF MIDDLE AND ERN TN INTO NRN AND CNTRL PORTIONS OF AL/GA AND
   EWD INTO THE WRN CAROLINAS...
   
   ...THERE IS A SLGT RISK OF SVR TSTMS FROM PARTS OF THE OH AND LOWER
   MS VALLEYS EWD TO THE CAROLINAS COASTS...
   
   ...TN VALLEY INTO NRN PARTS OF AL/GA...
   
   AN OUTBREAK OF SUPERCELLS CAPABLE OF VERY LARGE HAIL AND POTENTIALLY
   STRONG...LONG-TRACKED TORNADOES IS UNDERWAY TODAY ACROSS PARTS OF
   KY/MIDDLE TN INTO NWRN AL.  LATEST MESOANALYSIS INDICATES PRIMARY
   SURFACE LOW W OF HOP WHICH WILL CONTINUE ENEWD TOWARD THE MID
   ATLANTIC COAST BY SATURDAY MORNING.  MEANWHILE...RESIDUAL OUTFLOW
   BOUNDARY/EFFECTIVE WARM FRONT IS RAPIDLY LIFTING NWD WITH THIS
   FEATURE EXTENDING FROM INTERSECTION WITH ONGOING CONVECTION OVER SRN
   MIDDLE TN E-SEWD THROUGH NRN GA INTO NRN SC.
   
   WHILE SURFACE WINDS HAVE VEERED TO MORE SWLY IMMEDIATELY AHEAD OF
   ONGOING SUPERCELLS FROM NERN MS INTO NWRN AL...A CORRIDOR OF
   PRESSURE FALLS ALONG RETREATING WARM FRONT OVER SRN MIDDLE TN INTO
   NERN AL IS MAINTAINING MORE SLY BOUNDARY LAYER FLOW FARTHER TO THE
   E.  RESULTANT HODOGRAPH FROM HUNTSVILLE AL INDICATES A STRONGLY
   SHEARED KINEMATIC ENVIRONMENT WITH 30-35 KT OF 0-1 KM SHEAR AND
   60-70 KT OF BULK SHEAR IN THE LOWEST 6 KM.  THIS IN CONJUNCTION WITH
   THE VERY STEEP LAPSE RATES...SUFFICIENT BOUNDARY LAYER MOISTURE AND
   FAVORABLY LOW LCL/LFC HEIGHTS INDICATE A POTENTIAL FOR SIGNIFICANTLY
   TORNADIC SUPERCELLS ACROSS SRN MIDDLE AND SERN TN INTO NRN PARTS OF
   AL INTO NWRN GA THROUGH THIS AFTERNOON INTO EVENING.  IN ADDITION TO
   THE TORNADO THREAT...VERY LARGE HAIL WILL ALSO ACCOMPANY THESE
   STORMS.
   
   FOR ADDITIONAL SHORT TERM GUIDANCE ON THIS AREA...SEE MCD 430.
   
   REMAINING TEMPORAL AND SPATIAL ASPECTS OF DAY ONE PERIOD REMAIN WELL
   HANDLED IN THE 1630Z OUTLOOK.
   
   ..MEAD/EVANS/SMITH.. 04/10/2009
   
   .PREV DISCUSSION... /ISSUED 1123 AM CDT FRI APR 10 2009/
   
   ...OH/TN RIVER VALLEYS ACROSS CENTRAL GULF COAST STATES/SRN
   APPALACHIANS AND PORTIONS OF THE SOUTHEAST...
   
   OVERALL SETUP CONTINUES TO FAVOR A POSSIBLE OUTBREAK OF SEVERE
   THUNDERSTORMS ACROSS MUCH OF THE TN RIVER VALLEY/SRN APPALACHIANS
   AND ADJACENT AREAS THROUGH THE EVENING.  MORNING MODELS AND OBSERVED
   DATA TRENDS INDICATE LITTLE CHANGES ARE NECESSARY TO THE OUTLOOK. 
   15Z SURFACE MESOSCALE ANALYSIS AND VISIBLE IMAGERY INDICATE RESIDUAL
   OUTFLOW BOUNDARY FROM FAR UPSTATE SC/NRN GA NWWD INTO N-CENTRAL AL
   AND MIDDLE TN.  THIS BOUNDARY HAS CREATED AN AXIS OF GREATER
   MOISTURE /I.E. 60+F SFC DEW POINTS/ AND RESULTANT MLCAPE NOSING INTO
   MIDDLE TN LATE THIS MORNING.  IN ADDITION...MOSTLY CLEAR SKIES ARE
   SUPPORTING INCREASED MIXING AND VEERED SURFACE WINDS WITHIN WARM
   SECTOR ACROSS MUCH OF MS INTO FAR NWRN AL...AHEAD OF MAIN COLD FRONT
   NOW MOVING ACROSS THE MID SOUTH.  
   
   INTENSE/DEEP ASCENT IMMEDIATELY AHEAD OF UPPER LOW IS FOCUSING MOST
   ROBUST SEVERE THUNDERSTORM DEVELOPMENT LATE THIS MORNING FROM WRN KY
   INTO FAR NRN MS.  GREATEST BACKING OF SURFACE WINDS/SHEAR WILL
   LIKELY CONTINUE FROM THE TN RIVER VALLEY NWD TO THE OH RIVER VALLEY
   AS SURFACE LOW SHIFTS INTO CENTRAL KY.  ALTHOUGH QUESTIONS REMAIN
   ABOUT NWD EXTENT OF RICHER LOW LEVEL MOISTURE WHICH MAY BE TRAPPED
   FROM FAR S-CENTRAL KY SWD AS TRIPLE POINT SHIFTS ACROSS MIDDLE TN. 
   REGARDLESS...DEEP LAYER SHEAR AND SBCAPE WILL INCREASE THROUGH THE
   DAY AND SUPPORT AT LEAST A THREAT OF ISOLATED TORNADOES NWD TOWARDS
   THE OH RIVER WITH VERY COLD MID LEVEL TEMPERATURES OFFSETTING
   MARGINAL SURFACE MOISTURE.  THREAT WILL BE ENHANCED NEAR THE TRIPLE
   POINT OF OUTFLOW BOUNDARY AND NE-SW ORIENTED BROKEN LINE OF
   CONVECTION AS IT SHIFTS ACROSS SRN/MIDDLE TN THIS AFTERNOON AND INTO
   THE SRN APPALACHIANS THIS EVENING...INCLUDING POTENTIAL FOR A FEW
   STRONG AND/OR LONGER-LIVED TORNADIC SUPERCELLS.  ATTM...APPEARS
   SRN-MIDDLE/SERN TN AND NRN AL/NWRN GA WILL SEE GREATEST RISK OF
   DAMAGING TORNADOES.  
   
   S-SWWD EXTEND OF DEVELOPMENT INTO MS AND CENTRAL AL REMAINS MORE
   CONDITIONAL AS STRONGEST DEEP ASCENT AND OVERALL CONVERGENCE REMAIN
   WEAKER THAN POINTS FARTHER NORTH.  HOWEVER...SHEAR WILL BE QUITE
   STRONG /DESPITE THE MORE SWLY SURFACE WINDS/ AND MODERATE TO STRONG
   INSTABILITY WILL SUPPORT THREAT OF ISOLATED TORNADIC SUPERCELLS
   AND/OR SMALL BOWING LINES AS FRONT SETTLES SEWD THROUGH THE EVENING.
    
   LATER TONIGHT...LARGE SCALE UVV AHEAD OF UPPER VORT SHOULD
   STRENGTHEN E OF THE SRN APPALACHIANS AND THE REMAINDER OF THE
   CAROLINAS/SRN VA BY LATER TONIGHT.  BUT...WEAKER
   DESTABILIZATION...ASSOCIATED WITH A MORE LIMITED LOW-LEVEL MOISTURE
   RETURN AND ONSET OF DIURNAL COOLING...MAY MITIGATE SEVERE POTENTIAL.
    A LIMITED SEVERE THREAT SHOULD LINGER THROUGH EARLY SATURDAY
   MORNING...ESPECIALLY ALONG THE NC COAST...GIVEN AMOUNT OF SHEAR AND
   POSSIBILITY OF MODEST SBCAPE.
   
   CLICK TO GET WUUS01 PTSDY1 PRODUCT

   NOTE: THE NEXT DAY 1 OUTLOOK IS SCHEDULED BY 0100Z