The SPC is forecasting ...Severe thunderstorms expected over parts of the Lower/Middle Mississippi Valley and Tennessee Valley this afternoon and tonight....   Please read the latest public statement about this event.  View What is a Watch? clip.

   SPC AC 231937

   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0137 PM CST WED DEC 23 2015

   VALID 232000Z - 241200Z

   ...THERE IS A MDT RISK OF SVR TSTMS ACROSS PORTIONS OF
   AR...MO...IL...IND...KY...TN...AL...MS...

   ...THERE IS AN ENH RISK OF SVR TSTMS FROM NERN LA TO SWRN OH...

   ...THERE IS A SLGT RISK OF SVR TSTMS FROM THE CNTRL GULF COAST TO
   SRN LOWER MI...AND ACROSS THE CAROLINAS...

   ...THERE IS A MRGL RISK OF SVR TSTMS SURROUNDING THE SLGT RISK FROM
   THE CAROLINA COAST TO NRN LOWER MI...

   ...SUMMARY...
   AN OUTBREAK OF SEVERE THUNDERSTORMS AND TORNADOES IS FORECAST TODAY
   INTO TONIGHT FROM THE OHIO VALLEY INTO THE TENNESSEE AND LOWER
   MISSISSIPPI VALLEYS.  THE GREATEST RISK FOR A FEW
   INTENSE...LONG-TRACKED TORNADOES WILL EXIST OVER WESTERN TENNESSEE
   INTO NORTHERN MISSISSIPPI AND EASTERN ARKANSAS THIS AFTERNOON INTO
   TONIGHT.

   ...DISCUSSION...

   A FEW ADJUSTMENTS HAVE BEEN MADE TO 1630Z OUTLOOK...1) INCREASE
   SEVERE PROBS IMMEDIATELY AHEAD OF SFC LOW ALONG THE MO/IA BORDER 2)
   INCREASE SEVERE PROBS ACROSS THE CAROLINAS.

   1.  LATEST VIS IMAGERY DEPICTS INCREASING CU FIELD AHEAD OF SFC LOW
   FROM THE IA/MO BORDER...SWD INTO CNTRL MO.  WHILE LIGHTNING HAS YET
   TO DEVELOP IT APPEARS TSTMS WILL EVOLVE ACROSS THIS REGION AS
   CONVECTION DEEPENS.  LARGE-SCALE FORCING IS FOCUSED ACROSS THIS
   REGION AND A PLUME OF STEEP SFC-3KM LAPSE RATES ARE NUDGING INTO
   CNTRL MO.  THERE APPEARS TO BE AN INCREASING THREAT FOR SEVERE A BIT
   FARTHER NW THAN EARLIER INDICATED.

   2.  OUTFLOW IS SURGING EWD ALONG LEADING EDGE OF LONG-LIVED MCS OVER
   SC.  A FEW STRONG/SEVERE TSTMS ARE NOTED ALONG NRN EXTENT OF THIS
   LINE.  BOUNDARY-LAYER MOISTURE IS ADVANCING NWD ACROSS THE CAROLINAS
   WITHIN STRONGLY SHEARED ENVIRONMENT SUPPORTIVE OF SUPERCELLS.  HAVE
   INCREASED SEVERE PROBS TO ACCOUNT FOR ISOLATED TORNADOES AND
   DAMAGING WIND POTENTIAL.

   ACROSS THE MDT RISK...CONVECTION CONTINUES TO INCREASE IN INTENSITY
   AND COVERAGE ALONG A CORRIDOR FROM CNTRL AR...NEWD INTO WRN KY. 
   TORNADO THREAT WILL INCREASE ACROSS THIS REGION AS THE AFTERNOON
   PROGRESSES...IN LINE WITH EARLIER THOUGHTS.

   ..DARROW.. 12/23/2015

   .PREV DISCUSSION... /ISSUED 1034 AM CST WED DEC 23 2015/

   ...SYNOPSIS...

   A NEGATIVELY TILTED MID-LEVEL TROUGH FROM THE CNTRL HIGH PLAINS TO
   ARKLATEX WILL EJECT NEWD THROUGH THE MID-MS VALLEY INTO UPPER GREAT
   LAKES AHEAD OF AN AMPLIFYING UPSTREAM SYSTEM ALONG THE PACIFIC NW
   COAST.  AT THE SURFACE...AN AREA OF LOW PRESSURE OVER NERN KS WILL
   CONCURRENTLY DEVELOP NEWD TO CNTRL WI BY 24/00Z PRIOR TO REACHING
   CNTRL ONTARIO BY 12Z/THURSDAY.  MEANWHILE...A TRAILING COLD FRONT
   WILL SURGE EWD THROUGH THE MID-MS VALLEY INTO UPPER GREAT LAKES AND
   OH VALLEY WITH THE TRAILING EXTENSION OF THE FRONT ADVANCING MORE
   SLOWLY INTO THE LOWER-MS VALLEY.  ELSEWHERE...AN OUTFLOW
   BOUNDARY/RESIDUAL BAROCLINIC ZONE FROM CNTRL LA TO ALONG THE MS/AL
   COASTS AND THEN NEWD THROUGH E-CNTRL GA INTO THE CAROLINA PIEDMONT
   WILL ATTEMPT TO DEVELOP NWD/NWWD IN RESPONSE TO STRENGTHENING
   LOW-LEVEL SLY WINDS.

   ...OH VALLEY INTO THE TN AND LOWER-MS VALLEYS...

   MULTIPLE BANDS OF STRONG TO SEVERE STORMS ARE ONGOING AS OF MID
   MORNING FROM SRN IL TO CNTRL AR WITH THIS ACTIVITY LIKELY BEING
   FORCED BY A COMBINATION OF LOW-LEVEL WARM THERMAL AND MOISTURE
   ADVECTIONS...AND THE LEADING EDGE OF STRONGER MID-LEVEL HEIGHT
   FALLS/DCVA DOWNSTREAM OF THE MIGRATORY SHORT-WAVE TROUGH.  WHILE
   CLOUDS WILL LIKELY REMAIN FAIRLY WIDESPREAD ACROSS THE WARM
   SECTOR...POLEWARD FLUXES OF HEAT AND MOISTURE ALONG A
   BROADENING/STRENGTHENING SWLY LLJ WILL ALLOW FOR THE AIR MASS TO
   DESTABILIZE AHEAD OF THE ONGOING STORMS.  AFTERNOON MLCAPE VALUES
   ARE EXPECTED TO RANGE FROM 250-500 J/KG ACROSS THE OH VALLEY TO AS
   HIGH AS 1500-2500 J/KG OVER THE LOWER-MS VALLEY WHERE RICHER
   LOW-LEVEL MOISTURE AND THE POTENTIAL FOR STRONGER DAYTIME HEATING
   WILL RESIDE.

   LATEST CONVECTION-ALLOWING MODEL GUIDANCE REMAINS CONSISTENT WITH
   EARLIER DATA IN SUGGESTING THAT THE BOWING STRUCTURE OVER SERN
   MO/NERN AR WILL CONTINUE NEWD ALONG THE OH RIVER WITH AN ATTENDANT
   RISK FOR POTENTIALLY WIDESPREAD DAMAGING WINDS AND EMBEDDED
   TORNADOES GIVEN THE PRESENCE OF STRONG LOW-LEVEL AND DEEP-LAYER
   SHEAR.  FARTHER SW OVER ERN AR INTO WRN TN AND NRN MS...THE
   FAVORABLE OVERLAP OF MODERATE INSTABILITY AND STRONG VERTICAL SHEAR
   WILL YIELD AN ENVIRONMENT CONDUCIVE FOR TORNADIC SUPERCELLS THIS
   AFTERNOON INTO TONIGHT WHERE THE POTENTIAL WILL EXIST FOR A FEW
   INTENSE...LONG-TRACKED TORNADOES.  THIS CONVECTIVE REGIME
   --FEATURING REGENERATIVE/BACKBUILDING STORMS-- WILL PERSIST
   OVERNIGHT FROM THE TN VALLEY INTO LOWER-MS VALLEY WHERE A CONTINUED
   RISK FOR TORNADOES AND DAMAGING WINDS WILL EXIST.  

   ...CNTRL GULF COAST INTO CAROLINA PIEDMONT...

   THE INLAND FLUX OF HIGH THETA-E AIR FROM OFF THE GULF OF MEXICO WILL
   FOSTER AN INCREASE IN TSTMS ACROSS THE REGION TODAY WITH ACTIVITY
   LARGELY BEING FOCUSED ALONG THE RESIDUAL FRONT/OUTFLOW BOUNDARY
   WHICH WILL ATTEMPT TO DEVELOP NWD/NWWD.  GIVEN THE PRESENCE OF A
   MOIST AND AT LEAST MARGINALLY UNSTABLE AIR MASS COINCIDENT WITH THE
   ERN EDGE OF STRONGER DEEP-LAYER WIND FIELDS ATTENDANT TO THE CNTRL
   U.S. SYNOPTIC SYSTEM...A RISK FOR A FEW TORNADOES AND LOCALLY
   DAMAGING WINDS WILL EXIST WITH THE MOST INTENSE STORMS.

   ...MID-MS VALLEY...

   AN ADDITIONAL BAND OF TSTMS IS EXPECTED TO DEVELOP THIS AFTERNOON
   AHEAD OF THE MIGRATORY SURFACE LOW AND TRAILING COLD FRONT FROM
   PORTIONS OF ERN MO INTO WRN IL...ALONG THE CHANNEL OF STRONGEST
   MID-LEVEL HEIGHT FALLS ATTENDING THE UPPER-AIR SYSTEM.  POCKETS OF
   STRONGER HEATING AND RESIDUAL DEWPOINTS IN THE 50S WILL YIELD MLCAPE
   OF AROUND 500 J/KG AMIDST STRONG VERTICAL SHEAR.  AS SUCH THE
   POTENTIAL WILL EXIST FOR LOW-TOPPED SUPERCELLS AND BOWING STRUCTURES
   CAPABLE OF A FEW TORNADOES...DAMAGING WINDS AND PERHAPS SOME HAIL.

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