SPC AC 040600

   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0100 AM CDT FRI OCT 04 2013

   VALID 041200Z - 051200Z

   ...THERE IS A MDT RISK OF SVR TSTMS OVER EXTREME NERN NEB...EXTREME
   SERN SD...SRN MN AND CNTRL AND NRN IA...

   ...THERE IS A SLGT RISK OF SVR TSTMS FROM PORTIONS OF THE SRN AND
   CNTRL PLAINS INTO THE MID-UPPER MS VALLEY...

   ...SYNOPSIS...

   VIGOROUS SHORTWAVE TROUGH NOW MOVING INTO THE CNTRL INTERMOUNTAIN
   REGION WILL AMPLIFY A LITTLE FURTHER BEFORE ADVANCING EWD THROUGH
   THE CNTRL/NRN PLAINS AND UPPER MS VALLEY FRIDAY AND FRIDAY NIGHT. IN
   RESPONSE TO STRONG AGEOSTROPHIC FORCING ATTENDING AN UPPER JET
   ROTATING THROUGH BASE OF THE TROUGH...A LEE CYCLONE WILL DEEPEN
   AND LIFT NEWD THROUGH THE CNTRL PLAINS. BY EARLY EVENING THE LOW IS
   FORECAST TO BE OVER NERN NEB OR SERN SD WITH A TRAILING COLD FRONT
   SURGING SEWD THROUGH KS AND NWRN OK. A WARM FRONT WILL EXTEND EWD
   FROM THE LOW THROUGH THE UPPER MS VALLEY AND GREAT LAKES. A RESIDUAL
   CONVECTIVE OUTFLOW BOUNDARY WILL LIKELY LIFT NWD THROUGH CNTRL/NRN
   IA.

   ...MID-UPPER MS VALLEY REGION...

   ONGOING MCS OVER IA DRIVEN PRIMARILY BY ISENTROPIC ASCENT ON THE
   NOSE OF A STRONG SLY LLJ WILL LIKELY PERSIST INTO FRIDAY MORNING
   OVER THE UPPER MS VALLEY REGION. THIS ACTIVITY WILL SHIFT NEWD AND
   WEAKEN AS WARMER AIR ALOFT LIFTS NEWD AND CAPS THE BOUNDARY LAYER TO
   SFC BASED STORMS DURING MUCH OF THE AFTERNOON. REMNANT OUTFLOW
   BOUNDARY WILL PERSIST AND GRADUALLY MOVE NWD THROUGH IA AS 50 KT LLJ
   MIGRATES NNEWD THROUGH WARM SECTOR IN ASSOCIATION WITH THE
   DEVELOPING CYCLONE. RICH LOW-LEVEL MOISTURE WITH UPPER 60S DEWPOINTS
   RESIDING OVER THE MIDDLE MS VALLEY WILL ADVECT NWD THROUGH WARM
   SECTOR INCLUDING MUCH OF ERN NEB INTO IA AND POSSIBLY EXTREME SRN MN
   BENEATH REMNANT EML PLUME...LIKELY RESULTING IN A CORRIDOR OF
   1500-2000 J/KG MLCAPE. AS LLJ DEVELOPS NWD WITHIN DIVERGENT UPPER
   JET EXIT REGION...STORMS MAY INITIATE WITHIN ZONE OF ISENTROPIC
   ASCENT ALONG AND NORTH OF MODIFYING OUTFLOW BOUNDARY BY LATE
   AFTERNOON OR EARLY EVENING. PROVIDED MORNING STORMS
   DIMINISH...SUFFICIENT BOUNDARY LAYER RECOVERY MAY OCCUR TO SUPPORT
   SURFACE BASED STORMS. THIS ACTIVITY WILL EXIST WITHIN A VERY
   FAVORABLE KINEMATIC ENVIRONMENT WHERE NEAR SFC WINDS WILL BE BACKED
   TO ESELY BENEATH A STRONG LLJ RESULTING IN LARGE HODOGRAPHS.
   SUPERCELLS CAPABLE OF PRODUCING VERY LARGE HAIL AND TORNADOES WILL
   BE THE MAIN THREATS WITH THESE STORMS.

   ADDITIONAL STORMS MAY DEVELOP FARTHER WEST FROM SERN SD THROUGH ERN
   NEB NEAR THE SFC LOW AND SWD ALONG THE COLD FRONT AND MOVE EWD.
   SUPERCELLS CAPABLE OF LARGE HAIL AND TORNADOES WILL BE THE INITIAL
   THREATS. HOWEVER...SOME OF THE STORMS MAY EVENTUALLY CONSOLIDATE
   INTO LINE SEGMENTS WITH AN ATTENDANT DAMAGING WIND AND LARGE HAIL
   THREAT AS THEY CONTINUE EWD INTO THE EVENING.

   ...CNTRL THROUGH SRN PLAINS...

   THE PRE-FRONTAL WARM SECTOR WILL LIKELY BECOME MODERATELY TO
   STRONGLY UNSTABLE /2000-2500 J/KG MLCAPE/ AS REMNANT EML PLUME
   ADVECTS EWD ABOVE RICH LOW-LEVEL MOISTURE. HOWEVER...THIS WARM
   SECTOR WILL LIKELY REMAIN CAPPED TO SFC BASED STORMS UNTIL LATE
   AFTERNOON WHEN STRONG FORCING FOR ASCENT WILL ACCOMPANY THE SEWD
   SURGING COLD FRONT. GIVEN THE STRONG AND LINEAR NATURE OF THE
   FORCING...A RAPID UPSCALE GROWTH INTO LINES IS EXPECTED...BUT
   VERTICAL SHEAR WILL SUPPORT SOME ORGANIZED STRUCTURES WITHIN THE
   LINE INCLUDING SUPERCELLS AND BOWING SEGMENTS. LARGE HAIL AND
   DAMAGING WIND WILL BE THE MAIN THREATS FROM LATE AFTERNOON INTO THE
   EVENING.

   ...CNTRL GULF COASTAL AREA...

   LOW-LEVEL WINDS/SHEAR WILL UNDERGO A MODEST INCREASE AS TROPICAL
   STORM KAREN APPROACHES THE LA COAST LATE FRIDAY NIGHT. A LIMITED
   RISK FOR ISOLATED TORNADOES EXIST AS THE OUTER RAIN BANDS NE OF THE
   CENTER MOVE INLAND. AT THIS TIME IT APPEARS GREATER TORNADO THREAT
   WILL BE DELAYED UNTIL THE DAY 2 PERIOD WHEN KAREN MOVES CLOSER TO
   THE COAST. SEE LATEST NHC DISCUSSIONS FOR MORE INFORMATION ON KAREN.

   ..DIAL/SMITH.. 10/04/2013

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