SPC AC 182000

   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0300 PM CDT TUE JUN 18 2013

   VALID 182000Z - 191200Z

   ...THERE IS A SLGT RISK OF SVR TSTMS THIS AFTERNOON/EVENING ACROSS
   CENTRAL/SRN IL AND INDIANA...

   ...THERE IS A SLGT RISK OF SVR TSTMS ACROSS MUCH OF THE HIGH PLAINS
   THIS AFTERNOON/EVENING...

   ...THERE IS A SLGT RISK OF SVR TSTMS ACROSS NE ID/NW MT THIS
   AFTERNOON/EVENING...

   ...ERN GA INTO THE CAROLINAS...
   AN EXTENSIVE AREA OF SCTD STORMS HAS DEVELOPED OVER AL/GA EARLY THIS
   AFTERNOON WITH THE AREA OVER THE CAROLINA COASTAL PLAIN LARGELY VOID
   OF STORMS/CLOUD COVER PRIOR TO 20Z.  ALTHOUGH MODERATE WSWLY MID
   LEVEL FLOW HAS OVERSPREAD THE REGION AHEAD OF A WEAK DISTURBANCE
   MOVING ACROSS THE CAROLINAS/VA THIS AFTERNOON/EVENING...MODEST MID
   LEVEL LAPSE RATES OBSERVED ON THE MORNING AREA RAOBS HAVE LIMITED
   THE MAGNITUDE OF DESTABILIZATION DESPITE TEMPS RISING TO NEAR 90 DEG
   F.  9 KM CAPPI RADAR DATA INDICATES THE UPDRAFTS HAVE SO FAR
   REMAINED TEMPERED...AND EXPECTING THIS TREND TO CONTINUE INTO THE
   EARLY EVENING HOURS AS SCTD STORMS EVENTUALLY MOVE INTO THE CAROLINA
   COASTAL PLAIN...PERHAPS YIELDING A FEW POCKETS OF WIND DAMAGE.  AS A
   RESULT...HAVE REMOVED 15 PERCENT WIND PROBABILITIES GIVEN THE
   EXPECTED COVERAGE OF THE SEVERE WIND THREAT.

   ELSEWHERE...ONLY MINOR MODIFICATIONS HAVE BEEN MADE TO THE OUTLOOK. 
   THE MOST NOTABLE CHANGE INCLUDES A SOUTHWARD SHIFT OF THE 10 PERCENT
   THUNDERSTORM PROBABILITY LINE OVER THE SRN GREAT LAKES AND OVER THE
   NERN U.S. TO REFLECT VISIBLE SATELLITE TRENDS AND A CONFINING OF
   SEVERE HAIL/WIND PROBABILITIES OVER THE OH VALLEY WHERE AN AGITATED
   CU FIELD/COLD FRONT ARE LOCATED AS OF MID-AFTERNOON.

   ..SMITH/KERR.. 06/18/2013

   .PREV DISCUSSION... /ISSUED 1117 AM CDT TUE JUN 18 2013/

   ...CENTRAL AND SRN IL/INDIANA THIS AFTERNOON/EVENING...
   WATER VAPOR IMAGERY SHOWS AN EMBEDDED SHORTWAVE TROUGH MOVING ESEWD
   OVER IA...AND THIS WAVE WILL CROSS IL/INDIANA THIS
   AFTERNOON/EVENING.  THE MIDLEVEL WAVE COINCIDES WITH A FRONTAL ZONE
   ACROSS CENTRAL IL/INDIANA...WHICH WILL PROVIDE A FOCUS FOR
   THUNDERSTORM DEVELOPMENT THIS AFTERNOON.  MODIFIED 12Z SOUNDINGS
   FROM DVN/ILX SHOW THE POTENTIAL FOR MLCAPE OF 1500-2000 J/KG...WITH
   STEEP LOW-MIDLEVEL LAPSE RATES AND STRONG DEEP-LAYER VERTICAL SHEAR
   WHICH WILL SUPPORT A RISK FOR COUPLE OF SUPERCELLS CAPABLE OF
   PRODUCING LARGE HAIL AND DAMAGING WINDS.

   ...HIGH PLAINS THIS AFTERNOON/EVENING...
   FALLING PRESSURES ACROSS THE NRN ROCKIES...IN ADVANCE OF THE DEEP
   TROUGH MOVING INLAND OVER THE PAC NW...WILL INDUCE SELY UPSLOPE FLOW
   ACROSS THE CENTRAL HIGH PLAINS.  DEEP-LAYER BULK SHEAR WILL BE
   SUFFICIENT FOR SUPERCELLS WITH MODEST WLY FLOW ALOFT ABOVE SELY
   LOW-LEVEL FLOW...IN A STEEP LAPSE RATE ENVIRONMENT WITH 1500-2000
   J/KG MLCAPE.  EXPECT THUNDERSTORM INITIATION BY EARLY-MID AFTERNOON
   ALONG THE E SLOPES OF THE BIG HORN AND LARAMIE RANGES IN WY...AS
   WELL AS THE FRONT RANGE OF CO/NE NM...POSSIBLY AIDED BY WEAK ASCENT
   OVER NRN CO/WY IN ADVANCE OF A WEAK SHORTWAVE TROUGH EJECTING NEWD
   FROM UT.  STORMS WILL THEN SPREAD EWD THROUGH THE AFTERNOON/EVENING
   ONTO THE HIGH PLAINS...WITH AN ACCOMPANYING RISK FOR LARGE HAIL AND
   A FEW DAMAGING GUSTS.  SOME OF THE CONVECTION COULD PERSIST INTO
   TONIGHT ACROSS THE TX/OK PANHANDLES IN RESPONSE TO A DEVELOPING LLJ
   AND INCREASING MOISTURE FLUX FROM THE SE.

   ADDITIONAL STORMS COULD FORM THIS AFTERNOON ALONG A RESIDUAL OUTFLOW
   BOUNDARY ACROSS NW/W CENTRAL KS.  VERTICAL SHEAR WILL BE AT LEAST
   MARGINALLY FAVORABLE FOR SUPERCELLS WITH THE POTENTIAL TO PRODUCE
   ISOLATED HAIL/DAMAGING GUSTS.

   ...NW MT/NE ID THIS AFTERNOON/EVENING...
   LARGE SCALE ASCENT DOWNSTREAM FROM THE DEEP PAC NW TROUGH...AND THE
   NRN EXTENT OF A STEEP LAPSE RATE PLUME...WILL COMBINE WITH DAYTIME
   HEATING AND BOUNDARY LAYER DEWPOINTS IN THE UPPER 40S TO LOWER 50S
   TO SUPPORT MODERATE INSTABILITY AND THUNDERSTORM DEVELOPMENT BY MID
   AFTERNOON ACROSS NE ID/WRN MT.  STORMS WILL THEN SPREAD NNEWD OFF
   THE HIGHER TERRAIN...AND WILL BE CAPABLE OF PRODUCING AT LEAST
   ISOLATED DAMAGING WINDS AND LARGE HAIL.  THE STRONGEST VERTICAL
   SHEAR...AND GREATER POTENTIAL FOR SUPERCELLS...WILL BE NEAR THE
   BAROCLINIC ZONE ACROSS NW/N CENTRAL MT.

   ...ERN GA INTO THE ERN CAROLINAS THIS AFTERNOON...
   A MIDLEVEL SHORTWAVE TROUGH AND ASSOCIATED SURFACE LOW OVER THE SRN
   APPALACHIANS WILL PROGRESS EWD TO THE ATLANTIC COAST BY TONIGHT.  A
   WIDE SWATH OF THICK CLOUDS/RAIN ACCOMPANIES THIS TROUGH FROM THE MID
   ATLANTIC SWWD TO THE SRN APPALACHIANS AND PIEDMONT OF THE CAROLINAS.
    REGIONAL 12Z SOUNDINGS AND RECENT VWP/S REVEAL SOMEWHAT ENHANCED
   LOW-MIDLEVEL WSWLY FLOW OF 30-40 KT...THOUGH THE CLOUDS AND MOIST
   PROFILES/POOR LAPSE RATES WILL TEND TO LIMIT DESTABILIZATION THIS
   AFTERNOON...ASIDE FROM STRONGER SURFACE HEATING ACROSS THE COASTAL
   PLAINS WHERE MIDLEVEL FLOW WEAKENS.  THE NET RESULT IS A MARGINAL
   SITUATION FOR MULTICELL CLUSTERS WITH DAMAGING WINDS.

   ...E/SE TX INTO LA/MS THIS AFTERNOON...
   A WELL-DEVELOPED MCV FROM OVERNIGHT CONVECTION PERSISTS OVER N
   CENTRAL TX AS OF MID-LATE MORNING.  E-S OF THE MCV AND WEAK
   ASSOCIATED SURFACE LOW IN NE TX...DAYTIME HEATING AND CONVERGENCE
   ALONG WEAK SURFACE FRONTAL BOUNDARIES WILL SUPPORT THUNDERSTORM
   DEVELOPMENT.  DEEP-LAYER FLOW IS RELATIVELY WEAK WITHIN THE UNSTABLE
   WARM SECTOR...AND LAPSE RATES ALOFT ARE NOT STEEP.  ISOLATED WET
   MICROBURSTS WILL BE POSSIBLE THIS AFTERNOON...BUT SEVERE STORM
   COVERAGE SHOULD REMAIN RATHER SPARSE.

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