SPC AC 111622

   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   1122 AM CDT SUN MAY 11 2014

   VALID 111630Z - 121200Z

   ...THERE IS A MDT RISK OF SVR TSTMS OVER CNTRL KS INTO PARTS OF ERN
   NEB...WRN/CNTRL IA AND FAR NWRN MO...

   ...THERE IS A SLGT RISK OF SVR TSTMS FROM THE UPPER MIDWEST AND OH
   VALLEY INTO SRN PLAINS...

   ...SUMMARY...
   SEVERE THUNDERSTORMS ARE EXPECTED TO DEVELOP FROM PARTS OF THE
   CENTRAL AND SOUTHERN PLAINS THROUGH THE MID-MISSISSIPPI VALLEY INTO
   THE OHIO VALLEY TODAY THROUGH TONIGHT.  THE GREATEST CONCENTRATION
   OF SEVERE WEATHER SHOULD EXTEND FROM CENTRAL AND NORTHERN KANSAS
   THROUGH SOUTHEAST NEBRASKA INTO MUCH OF IOWA.  VERY LARGE
   HAIL...DAMAGING WIND...AND TORNADOES WILL OCCUR. A COUPLE OF INTENSE
   TORNADOES WILL BE POSSIBLE THIS AFTERNOON INTO EVENING OVER PARTS OF
   EASTERN NEBRASKA INTO WESTERN AND PERHAPS CENTRAL IOWA.

   ...SYNOPSIS...

   12Z UPPER-AIR DATA INDICATE MID AND UPPER-LEVEL JET STREAKS
   PROGRESSING THROUGH THE BASE OF THE PARENT TROUGH OVER THE LOWER CO
   VALLEY. THESE WIND MAXIMA WILL CONTINUE EWD/NEWD INTO THE CNTRL/SRN
   HIGH PLAINS BY 12/12Z...IN TANDEM WITH THE SRN EXTENSION OF
   FULL-LATITUDE TROUGH. A 40-50+ KT SLY LLJ WILL BE MAINTAINED AHEAD
   OF THE TROUGH ACROSS THE CNTRL/SRN PLAINS TODAY WITH THIS FEATURE
   MIGRATING EWD/NEWD INTO THE UPPER MIDWEST AND OZARK PLATEAU REGION
   BY EARLY MONDAY.

   AT THE SURFACE...A LEE CYCLONE OVER WRN KS MAY WEAKEN SLIGHTLY WHILE
   DEVELOPING NEWD INTO N-CNTRL IA OR S-CNTRL/SERN MN BY THE END OF THE
   DAY ONE PERIOD. AN ASSOCIATED WARM FRONT /REINFORCED BY CONVECTIVE
   OUTFLOW/ WILL ATTEMPT TO MOVE NWD THROUGH PARTS OF ERN NEB AND
   SRN/CNTRL IA WHILE A COLD FRONT SURGES SWD THROUGH THE CNTRL INTO
   SRN HIGH PLAINS. THE COLD FRONT WILL GRADUALLY OVERTAKE A DRYLINE
   WHICH WILL BECOME ESTABLISHED FROM N-CNTRL KS SSWWD INTO THE FAR ERN
   OK/TX PNHDLS INTO W-CNTRL TX BY MID/LATE AFTERNOON. 

   ...MID/LOWER MO VALLEY INTO CNTRL PLAINS TODAY THROUGH TONIGHT...

   MORNING RAOB DATA FROM TOP AND SGF SHOW THAT CONSIDERABLE MOISTENING
   OF THE WARM SECTOR HAS OCCURRED OVERNIGHT WITH LOWEST 100-MB
   MEAN-MIXING RATIOS OF AROUND 13 G/KG AND BOUNDARY LAYER DEWPOINTS IN
   THE MID 60S. THIS MOISTURE WILL COMBINE WITH DAYTIME HEATING AND
   STEEP MIDLEVEL LAPSE RATES TO YIELD AFTERNOON MLCAPE VALUES
   APPROACHING 2500-3500+ J/KG.

   THE REMNANTS OF A NOCTURNAL MCS ONGOING OVER WRN/CNTRL IA HAVE
   RECENTLY SHOWN SIGNS OF RE-INTENSIFICATION OWING TO THE GRADUAL
   DESTABILIZATION OF THE AIR MASS ALONG THE NWD-MOVING WARM FRONT. A
   GROWING RISK FOR DAMAGING WINDS...LARGE HAIL AND PERHAPS A TORNADO
   OR TWO WILL EXIST WITH THIS SYSTEM AS IT CONTINUES EWD TODAY. FOR
   ADDITIONAL NEAR-TERM GUIDANCE...SEE MCD 561.

   IN THE WAKE OF THE MORNING STORMS...RAPID TSTM DEVELOPMENT IS
   ANTICIPATED FROM THE VICINITY OF THE SURFACE TRIPLE POINT OVER
   S-CNTRL NEB SWWD ALONG THE COLD FRONT AND DRYLINE INTO WRN KS. AMPLE
   VERTICAL SHEAR WILL EXIST FOR SUPERCELLS AS THE INITIAL STORM MODE
   WITH A RISK FOR VERY LARGE HAIL AND TORNADOES. HOWEVER...THE LARGELY
   PARALLEL ORIENTATION OF THE DEEP-LAYER SHEAR VECTOR TO THE COLD
   FRONT AS IT OVERTAKES THE DRYLINE SUGGESTS A FAIRLY QUICK UPSCALE
   GROWTH OF STORMS INTO A LINEAR MCS. THE EXCEPTION MAY BE ACROSS
   PARTS OF ERN NEB INTO WRN AND CNTRL IA THIS AFTERNOON AND EVENING
   WHERE STRONG LOW-LEVEL SHEAR /I.E. EFFECTIVE SRH VALUES OF 300-400
   M2 PER S2/ AND A MORE FAVORABLE DEEP-LAYER SHEAR VECTOR ORIENTATION
   SUGGEST A GREATER RISK FOR TORNADOES /SOME POSSIBLY INTENSE/ GIVEN A
   MORE DISCRETE STORM MODE.

   EXPECT ONE OR MULTIPLE BOWING MCS/S TO EVOLVE TONIGHT WITH A HAIL
   AND DAMAGING WIND THREAT SPREADING EWD INTO THE MIDWEST/UPPER
   MIDWEST AND LOWER MO VALLEY.

   ...SRN PLAINS THIS AFTERNOON INTO TONIGHT...

   STRONG HEATING W OF THE DRYLINE COUPLED WITH WEAK HEIGHT FALLS ALOFT
   WILL LIKELY PROMOTE ISOLATED STORM DEVELOPMENT BY LATE
   AFTERNOON/EARLY EVENING. FORECAST SOUNDINGS INDICATE THAT
   CONSIDERABLE BOUNDARY LAYER MIXING WILL RESULT IN 30+ T-TD SPREADS
   JUST E OF THE DRYLINE WITH STEEP LOW TO MIDLEVEL LAPSE RATES
   CONTRIBUTING TO MLCAPE OF 1500-3000 J/KG. ASSOCIATED HODOGRAPHS
   EXHIBIT A VERTICALLY VEERING WIND PROFILE WITH 30-40 KT OF
   DEEP-LAYER SHEAR WHICH WILL BE SUFFICIENT FOR SUPERCELLS CAPABLE OF
   VERY LARGE HAIL.

   THE MAJORITY OF THESE DIURNALLY DRIVEN STORMS ARE EXPECTED TO
   DIMINISH WITH NIGHTFALL OWING TO THE DE-COUPLING OF THE BOUNDARY
   LAYER. HOWEVER...SOME TSTM ACTIVITY --INCLUDING AN ISOLATED RISK FOR
   DAMAGING WINDS AND HAIL-- MAY PERSIST OVERNIGHT ALONG THE
   EWD/SEWD-MOVING COLD FRONT.

   ...UPPER MIDWEST INTO MID MS/OH VALLEYS THIS AFTERNOON INTO
   TONIGHT...

   DESPITE THE PRESENCE OF MIDLEVEL RIDGING DOWNSTREAM FROM THE
   EVOLVING WRN U.S. TROUGH...INCREASING LOW-LEVEL MOISTURE...DAYTIME
   HEATING AND STRENGTHENING MIDLEVEL LAPSE RATES FROM THE WEST WILL
   PROMOTE MODERATE INSTABILITY BY AFTERNOON WITH MLCAPE OF 1000-2000
   J/KG. SPECIFIC DETAILS REGARDING STORM DEVELOPMENT AND EVOLUTION
   REMAIN UNCLEAR...BUT THE PRESENCE OF A NWD-MOVING WARM FRONT AND
   EXISTING CONVECTIVE OUTFLOWS MAY SERVE AS FOCI FOR TSTM DEVELOPMENT
   LATER TODAY. OTHER STORMS ONGOING ACROSS IA/NRN MO WILL LIKELY BEGIN
   TO AFFECT PARTS OF THE REGION THIS AFTERNOON INTO EVENING. WHILE
   VERTICAL SHEAR WILL BE WEAKER THAN POINTS TO THE W...THE DEGREE OF
   INSTABILITY WILL SUPPORT ORGANIZED STORM STRUCTURES WITH A RISK FOR
   PRIMARILY DAMAGING WINDS AND SEVERE HAIL.

   ..MEAD/MOSIER.. 05/11/2014

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