SPC AC 211727

   DAY 1 CONVECTIVE OUTLOOK CORR 1
   NWS STORM PREDICTION CENTER NORMAN OK
   1227 PM CDT SUN JUN 21 2015

   VALID 211630Z - 221200Z

   ...THERE IS AN ENH RISK OF SVR TSTMS ACROSS PORTIONS OF THE DAKOTAS
   LATE TODAY AND TONIGHT...

   ...THERE IS AN ENH RISK OF SVR TSTMS FROM CENTRAL MO EAST TO
   SOUTHERN IL...

   ...THERE IS A SLGT RISK OF SVR TSTMS ACROSS THE NORTHERN PLAINS TO
   UPPER MISSISSIPPI VALLEY...

   ...THERE IS A SLGT RISK OF SVR TSTMS FROM THE LOWER MISSOURI RIVER
   VALLEY TO THE MIDWEST/OHIO VALLEY...

   ...THERE IS A MRGL RISK OF SVR TSTMS FROM THE NORTHERN HIGH PLAINS
   ACROSS THE NORTHERN PLAINS/MIDDLE MISSISSIPPI VALLEY TO OH
   VALLEY/MID ATLANTIC AND SOUTH...

   CORRECTED TO ADD MARGINAL RISK TO SOUTH.

   ...SUMMARY...
   SEVERE STORMS CAPABLE OF VERY LARGE HAIL...TORNADOES...AND
   POTENTIALLY WIDESPREAD DAMAGING WINDS ARE PROBABLE THIS AFTERNOON
   INTO TONIGHT FROM THE NORTHERN HIGH PLAINS INTO UPPER MISSISSIPPI
   VALLEY. SCATTERED SEVERE THUNDERSTORMS WITH A RISK FOR MAINLY LARGE
   HAIL AND DAMAGING WINDS ARE POSSIBLE FROM THE LOWER MISSOURI VALLEY
   TO CENTRAL APPALACHIANS.

   ...LOWER MO VALLEY TO MIDWEST/LOWER OH VALLEY...
   BROKEN BAND OF LOCALLY INTENSE STORMS/SUPERCELLS FROM EXTREME
   NORTHEAST KS ACROSS NORTHERN MO WERE SITUATED ON THE LEADING EDGE OF
   PRONOUNCED EML PLUME EMANATING FROM CENTRAL PLAINS HEAT DOME. LIFT
   ACROSS WEST-EAST QUASI-STATIONARY BOUNDARY WAS LIKELY BEING ENHANCED
   AS A LOW AMPLITUDE SHORT WAVE TROUGH APPROACHES THE AREA FROM NEB.
   CONTINUED STRONG HEATING ACROSS SOUTHWEST AND CENTRAL MO SHOULD
   REMOVE ANY REMAINING CONVECTIVE INHIBITION AND RESULT IN ABUNDANT
   INSTABILITY TO FUEL ADDITIONAL INTENSE CONVECTION...EVENTUAL
   CONSOLIDATION...AND UPSCALE GROWTH. THE TIMING OF THIS TRANSITION
   INTO ONE OR MORE FORWARD PROPAGATING SYSTEMS...AND AN INCREASING
   THREAT FOR DAMAGING WINDS...REMAINS SOMEWHAT UNCERTAIN GIVEN
   RELATIVELY EARLY STORM INITIATION AND CURRENT DISCRETE AND ELEVATED
   NATURE OF ONGOING STORMS. HOWEVER...MAGNITUDE OF AVAILABLE
   INSTABILITY AND PRESENCE OF 40-50 KT MID-LEVEL FLOW DIRECTED INTO
   POSSIBLE DEVELOPING/INCREASING CONVECTIVE COLD POOLS...SHOULD FAVOR
   ORGANIZED LINES/BOWS SPREADING EAST-SOUTHEAST FROM CENTRAL MO INTO
   IL AND POSSIBLY THE LOWER OH VALLEY THROUGH THIS AFTERNOON AND
   EVENING.

   ...MT ACROSS DAKOTAS TO UPPER MS VALLEY LATE...
   ANOTHER ROUND OF SEVERE STORMS APPEARS LIKELY ACROSS THE NORTHERN
   HIGH PLAINS COMMENCING LATE THIS AFTERNOON AND CONTINUING INTO LATE
   TONIGHT. IN THE WAKE OF NUMEROUS RECENT DAILY/NIGHTLY
   EVENTS...RICHER LOW LEVEL MOISTURE HAS BEEN SHUNTED WELL SOUTH OF
   THE REGION THIS MORNING. HOWEVER...A NARROW RIBBON OF RETURN FLOW
   HAS ALREADY BECOME ESTABLISHED FROM WESTERN NEB NORTHWARD TO THE
   WESTERN DAKOTAS WHILE PERSISTENT WESTERLY FLOW ALOFT ACTS TO
   MAINTAIN STEEPER LAPSE RATE PLUME FROM THE CONTINENTAL DIVIDE
   EASTWARD.

   LEE-TROUGHING IN THE PRESENCE OF MODEST WESTERLY FLOW ALOFT WILL ACT
   TO FOCUS LOW LEVEL FORCING AND STORM INITIATION OVER EASTERN MT AS
   DIURNAL DESTABILIZATION AND STORM INITIATION OCCURS THROUGH THE
   AFTERNOON. ADDITIONAL STORMS ARE LIKELY ACROSS THE HIGHER TERRAIN AS
   UPSTREAM SHORT WAVE TROUGHS ACROSS PACIFIC NORTHWEST AND SOUTHERN BC
   BEGIN TO PHASE AND PRODUCE WEAK HEIGHT FALLS ACROSS THE REGION. BOTH
   AREAS OF CONVECTION WILL LIKELY PERSIST AS LEE CYCLONE ORGANIZES AND
   TRACKS EAST TO THE DAKOTAS TONIGHT.

   PRONOUNCED MASS AND MOISTURE FLUXES ARE INDICATED IN LATEST GUIDANCE
   ACROSS THE NORTHERN PLAINS THROUGH LATE TONIGHT AS STRONGER HEIGHT
   FALLS EMERGE ACROSS THE REGION AND AID DEEP-LAYER ASCENT AND FURTHER
   INTENSIFICATION OF SURFACE LOW. CONSOLIDATION OF LATE DAY/EVENING
   STORMS INTO ONE OR MULTIPLE MCSS WILL LIKELY OCCUR AS THIS ACTIVITY
   ACCELERATES EASTWARD TOWARD THE UPPER MS VALLEY THROUGH EARLY MONDAY
   ON THE NOSE OF THE STRENGTHENING MID-LEVEL JET STREAK. VERY STEEP
   LAPSE RATES ALOFT...MUCAPE OF 2000-4000+ J/KG AND INTENSE VERTICAL
   SHEAR WILL SUPPORT ELEVATED SUPERCELLS CAPABLE OF LARGE HAIL AND
   POSSIBLE UPSCALE EVOLUTION INTO SEVERE BOW ECHO FORMATION WITH
   ATTENDANT RISK FOR SIGNIFICANT WIND DAMAGE.

   ...OH/KY/WV TO MID ATLANTIC...
   A NUMBER OF WEAK PERTURBATIONS EMBEDDED WITHIN A BROAD ZONE OF
   40-50KT CYCLONIC FLOW ALOFT MAY ACT TO ENHANCE ASCENT ALONG REMNANT
   CONVECTIVE OUTFLOW BOUNDARIES/WEAK FRONTAL SEGMENTS AND ZONES OF
   DIFFERENTIAL HEATING TO SPUR AT LEAST A FEW STRONG/SEVERE STORMS
   THIS AFTERNOON. GREATEST RISK OF MARGINALLY SEVERE HAIL AND DAMAGING
   WINDS WILL BE IN THOSE AREAS WITH GREATEST ONGOING HEATING AND
   DESTABILIZATION FROM SOUTHERN AND EASTERN OH TO KY/WV TO THE MID
   ATLANTIC. GIVEN LACK OF STRONGER FORCING FOR ASCENT...OVERALL SEVERE
   STORM COVERAGE AND MODE/EVOLUTION REMAINS SOMEWHAT UNCERTAIN.

   ...SOUTH/SOUTHEAST...
   ISOLATED PULSE STORMS FORMING IN THE HEAT OF THE AFTERNOON WILL POSE
   SOME CHANCE FOR RANDOM STRONG TO LOCALLY SEVERE DOWNBURST WINDS.

   ..CARBIN/COOK.. 06/21/2015

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