SPC Convective Outlook for June 12, 2013


   SPC AC 120616

   DAY 1 CONVECTIVE OUTLOOK CORR 1
   NWS STORM PREDICTION CENTER NORMAN OK
   0116 AM CDT WED JUN 12 2013

   VALID 121200Z - 131200Z

   ...THERE IS A MDT RISK OF SVR TSTMS FROM NRN IL INTO IND AND WRN
   OH...

   ...THERE IS A SLGT RISK OF SVR TSTMS FROM IA EWD ACROSS A LARGE PART
   OF THE OH VALLEY AND INTO VA/MD...

   ...THERE IS A SLGT RISK OF SVR TSTMS ACROSS MUCH OF MT...ERN
   ID...AND NRN WY...

   CORRECTED FOR WORDING

   ...WIDESPREAD DAMAGING WINDS...LARGE HAIL AND A FEW TORNADOES
   EXPECTED ACROSS A LARGE AREA FROM IA INTO WV...

   ...SYNOPSIS...
   A POTENT SHORTWAVE TROUGH WILL MOVE FROM THE CNTRL PLAINS EWD INTO
   IA/MO/IL BY 00Z...AND WILL CONTINUE ESEWD ACROSS THE OH VALLEY AND
   WILL APPROACH THE APPALACHIANS BY 12Z THU. AT THE SURFACE...LOW
   PRESSURE WILL MOVE FROM ERN NEB INTO ERN IA/NRN IL BY LATE
   AFTERNOON...WITH DIFFUSE WARM FRONT FROM SRN WI INTO LOWER MI DURING
   THE DAY...THEN SHIFTING NWD ACROSS PA INTO THUR MORNING. A COLD
   FRONT WILL TRAIL THE LOW AS IT DEEPENS OVERNIGHT...EXTENDING FROM OH
   SWWD ALONG THE OH RIVER THUR MORNING.

   TO THE W...A LARGE UPPER TROUGH WILL SLOWLY PIVOT EWD ACROSS THE
   PACIFIC NW...WITH SWLY FLOW ALOFT ACROSS IA/WY/MT AND AN INVERTED
   SURFACE TROUGH FOCUSING DAYTIME STORMS THERE.

   ...IA...IL AND SRN WI EARLY AFTERNOON INTO IND...OH...NRN KY AND FAR
   SRN MI DURING THE EVENING...
   MORNING STORMS ARE EXPECTED TO BE IN PROGRESS ACROSS SRN MN/IA AND
   VICINITY...WITH SOME MARGINAL SEVERE WIND/HAIL THREAT. AS THE LOW
   DEVELOPS...THESE STORMS WILL LIKELY BEGIN TO GROW UPSCALE WITH A
   RAPIDLY DESTABILIZING AIR MASS TO THE E. OTHER CONVECTION MAY ALSO
   FORM ALONG THE WARM FRONT E OF THE SURFACE LOW TRACK...ACROSS SRN
   WI/NRN IL. INITIALLY...SOME OF THESE CELLS ARE LIKELY TO BE
   SUPERCELLS...AND A STRONG TORNADO COULD OCCUR. WITH TIME...AND
   PARTIALLY DUE TO WEAK UPPER LEVEL FLOW...STORMS SHOULD MERGE INTO A
   LARGE CLUSTER. INCREASING WIND FIELDS WILL FAVOR A FORWARD
   PROPAGATING CONVECTIVE SYSTEM...POSSIBLY A DERECHO CAPABLE OF
   WIDESPREAD DAMAGING WINDS. HOWEVER...EMBEDDED AREAS OF ROTATION MAY
   ALSO EXIST PERIODICALLY...INDICATING EITHER TORNADOES OR ENHANCED
   SWATHS OF DAMAGING WIND POTENTIAL. LARGE HAIL IS ALSO
   LIKELY...POSSIBLY WIND DRIVEN.

   MODELS INDICATE THE MAIN CORRIDOR FOR WIDESPREAD DAMAGE WILL BE FROM
   NRN IL INTO NRN AND CNTRL IND AND INTO OH. HOWEVER...IF THE SYSTEM
   GROWS LARGER THAN EXPECTED...OTHER AREAS COULD BE UNDER A GREATER
   THREAT SUCH AS NRN KY...WV...AND WRN PA. 

   ...SRN MI INTO OH...WV...WRN PA LATE AFTERNOON...
   ALTHOUGH THE MAIN SURFACE LOW WILL BE OVER IL AT THIS TIME...A BROAD
   AREA OF CONVERGENCE WILL EXIST NEAR A DIFFUSE WARM FRONT FROM SRN
   LOWER MI INTO OH. FORECAST SOUNDINGS SHOW EXTREME
   INSTABILITY...STEEP LAPSE RATES...AND VEERING WINDS WITH HEIGHT
   WHICH WILL FAVOR SUPERCELLS CAPABLE OF VERY LARGE HAIL AND
   TORNADOES.

   ...SRN IL AND IND INTO WRN KY DURING THE EVENING...
   THE SRN EXTENT OF THE CONVECTIVE SYSTEM...EITHER NEAR THE FRONT OR
   ALONG SURGING OUTFLOW...IS MOST LIKELY TO BE FROM SRN IL INTO WRN KY
   DURING THE LATE AFTERNOON/EVENING. HOWEVER...THERE WILL BE A
   CONDITIONAL THREAT OF SEVERE WIND AND HAIL...AND PERHAPS ISOLATED
   TORNADOES IN THESE AREAS...AND PERHAPS A BIT FARTHER S AS IT WILL
   REMAIN QUITE UNSTABLE.

   ...VA INTO THE DELMARVA - AFTERNOON...
   BRIEF SHORTWAVE RIDGING WILL OCCUR DURING THE DAY WELL AHEAD OF THE
   OH VALLEY SYSTEM...WITH STRONG HEATING AND INSTABILITY DEVELOPING.
   WEAK CONVERGENCE WITHIN THE SFC TROUGH MAY BE ENOUGH FOR ISOLATED
   STORMS CAPABLE OF HAIL OR WIND DURING THE AFTERNOON. THEN
   OVERNIGHT...INSTABILITY AND SHEAR PROFILES WILL CONDITIONALLY BE
   FAVORABLE FOR SEVERE WEATHER...BUT THE MAIN CONVECTIVE COMPLEX MAY
   REMAIN MAINLY NW OF THE AREA AS THE MAIN SURGE IS EXPECTED ACROSS OH
   AND WRN PA. HOWEVER...SUBSEQUENT OUTLOOKS WILL REASSESS AS NEW DATA
   INCLUDING SPECIAL SOUNDINGS BECOME AVAILABLE.

   ...MT...ERN ID...NRN WY...
   DAYTIME HEATING...COOL PROFILES ALOFT AND WEAK SURFACE CONVERGENCE
   WILL HELP INITIATE SCATTERED THUNDERSTORMS DURING THE AFTERNOON. THE
   STEEP LAPSE RATES AND AMPLE DEEP LAYER SHEAR WILL FAVOR SUPERCELLS
   CAPABLE OF MAINLY LARGE HAIL...ALTHOUGH A FEW DAMAGING WIND GUSTS
   COULD OCCUR WITH SMALL BOWING CELLS. GIVEN BACKED SURFACE FLOW AND
   FAVORABLE STORM MODE...A BRIEF TORNADO CANNOT BE RULED OUT.

   ..JEWELL.. 06/12/2013

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