SPC AC 261957

   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0257 PM CDT SAT APR 26 2014

   VALID 262000Z - 271200Z

   ...THERE IS A SLGT RISK OF SVR TSTMS FROM WRN TX NWD INTO SERN SD...

   ...SUMMARY...
   ISOLATED SEVERE STORMS WILL BE POSSIBLE LATE THIS AFTERNOON INTO
   TONIGHT FROM PARTS OF WEST TEXAS NORTHWARD ACROSS OKLAHOMA AND
   KANSAS TO THE ADJACENT AREAS OF NEBRASKA...IOWA...AND SOUTH DAKOTA. 
   THE PRIMARY THREATS WILL BE LARGE HAIL AND DAMAGING WIND GUSTS.

   ...OK INTO NWRN TX...
   TEMPERATURES CONTINUE TO RISE ACROSS THE SRN PLAINS WITH 90S F
   ACROSS NWRN TX AND SWRN OK. DESPITE SLY SURFACE WINDS...DEWPOINTS
   CONTINUE TO MIX INTO THE 50S F EXCEPT FOR 60S F NEAR THE I-35
   CORRIDOR. THE STEEP LOW TO MIDLEVEL LAPSE RATE ENVIRONMENT SHOULD
   RESULT IN ISOLATED DAYTIME STORMS...BUT BACKING SURFACE WINDS NEAR
   THE DRYLINE IS REDUCING CONVERGENCE. A CONDITIONAL THREAT OF A FEW
   HIGH-BASED SUPERCELLS REMAIN THIS AFTERNOON AND EVENING...WITH HAIL
   AND LOCALLY STRONG WINDS POSSIBLE.

   OVERNIGHT...ALTHOUGH CAPPING INCREASES...SO DOES LOW-LEVEL MOISTURE.
   IN ADDITION...FORCING FOR ASCENT WILL INCREASE DUE TO RAPID COOLING
   ALOFT AND HEIGHT FALLS. A CONDITIONAL THREAT OF LARGE HAIL AND
   LOCALLY STRONG WIND GUSTS WILL EXIST...BUT THE OVERALL COVERAGE OF
   SEVERE IS LIKELY TO BE ISOLATED.

   ..JEWELL.. 04/26/2014

   .PREV DISCUSSION... /ISSUED 1127 AM CDT SAT APR 26 2014/

   ...SYNOPSIS...
   AN INTENSE MIDLEVEL SHORTWAVE TROUGH OVER THE LOWER CO RIVER VALLEY
   THIS MORNING WILL PROGRESS EWD TO THE SRN/CENTRAL HIGH PLAINS BY
   EARLY SUNDAY.  ASSOCIATED STRONG SURFACE CYCLOGENESIS WILL OCCUR
   FROM NE CO THIS AFTERNOON TO SW NEB OVERNIGHT...WITH A SHARPENING
   LEE TROUGH/DRYLINE SWD FROM WRN KS TO NW TX.  LOW-LEVEL MOISTURE
   WILL SPREAD NWD TODAY IN ADVANCE OF THE LEE TROUGH...WITH LOW 60S
   BOUNDARY LAYER DEWPOINTS REACHING CENTRAL ERN KS BY THIS
   EVENING...MID 60S INTO S/SW OK...AND UPPER 60S CENTRAL TX.  THIS
   MOISTENING WILL OCCUR BENEATH STEEP MIDLEVEL LAPSE RATES OBSERVED IN
   REGIONAL 12Z SOUNDINGS...WITH MODERATE-STRONG BUOYANCY EXPECTED IN
   THE WARM SECTOR THIS AFTERNOON INTO TONIGHT.

   ...NW TX TO WRN OK LATE AFTERNOON THROUGH TONIGHT...
   DESPITE THE INCREASINGLY FAVORABLE BACKGROUND PATTERN...THERE ARE
   SEVERAL CONCERNS REGARDING STORM DEVELOPMENT TODAY.  THE PRIMARY
   LIMITING FACTOR IS THE MAGNITUDE OF THE CAP VERSUS THE DEGREE OF
   LOW-LEVEL MOISTENING.  THE EML IS RELATIVELY WARM AND AFTERNOON
   SURFACE CONDITIONS WITH LOW-MID 60S DEWPOINTS AND MID 80S
   TEMPERATURES WILL LIKELY REMAIN CAPPED...WITH DEEPER MIXING AND
   TEMPERATURES IN THE 90S NECESSARY TO REMOVE CONVECTIVE INHIBITION
   ALONG THE DRYLINE.  ASSUMING THE OBSERVED THIN CIRRUS CLOUDS DO NOT
   HINDER SURFACE HEATING MUCH...ISOLATED HIGH-BASED STORMS MAY FORM BY
   00Z ALONG THE NW TX/SW OK PORTION OF THE DRYLINE WHERE THE WARMEST
   SURFACE TEMPERATURES COINCIDE WITH THE W EDGE OF THE RICHER
   MOISTURE.  IF SUCH DEVELOPMENT OCCURS...MLCAPE NEAR 3000 J/KG AND
   SUFFICIENT DEEP-LAYER SHEAR WILL SUPPORT A RISK FOR SUPERCELLS WITH
   VERY LARGE HAIL.  THE LATER ARRIVAL OF THE LOW-LEVEL MOISTURE CASTS
   EVEN MORE DOUBT ON AFTERNOON DRYLINE STORM DEVELOPMENT FARTHER N
   INTO KS. 

   THERE WILL BE A CONDITIONAL TORNADO RISK IN A NARROW WINDOW LATE
   THIS EVENING WHEN LOW-LEVEL MOISTURE BACKS NWWD INTO THE AFTERNOON
   DRYLINE POSITION/ZONE OF POTENTIAL HIGH-BASED STORM DEVELOPMENT...
   AND AS THE SLY LLJ STRENGTHENS.  MLCAPE WILL REMAIN NEAR 3000 J/KG
   INTO EARLY TONIGHT AS DEWPOINTS INCREASE INTO THE MID 60S FROM NW TX
   INTO OK...AND EFFECTIVE SRH WILL INCREASE TO AOA 300 M2/S2. 
   STILL...CONVECTIVE INHIBITION WILL BE RELATIVELY LARGE WITH SLOW
   SURFACE COOLING...AND LARGE-SCALE FORCING FOR ASCENT WILL BE WEAK
   UNTIL LATE TONIGHT WHEN THE SHORTWAVE TROUGH APPROACHES THE HIGH
   PLAINS.  THUS...WILL MAINTAIN A CONDITIONAL SEVERE STORM RISK...BUT
   STORM COVERAGE MAY BE SPARSE.

   ...OK/KS TO THE MID MO VALLEY OVERNIGHT...
   THE ARRIVAL OF THE STRONGER HEIGHT FALLS COULD PROMOTE ELEVATED
   THUNDERSTORM DEVELOPMENT 06-12Z FROM WRN/CENTRAL OK INTO CENTRAL
   KS...WHERE LARGE HAIL AND ISOLATED DAMAGING GUSTS WILL BE THE MAIN
   THREATS.  OTHER ELEVATED CONVECTION WITH THE RISK FOR LARGE HAIL
   WILL ALSO BE POSSIBLE TONIGHT IN THE ZONE OF STRONGER LOW-LEVEL WAA
   FROM NE NEB/SE SD INTO WRN IA.  

   ...ERN WY/SW SD/NW NEB THIS AFTERNOON/EVENING...
   SOME HIGH-BASED CONVECTION COULD FORM THIS AFTERNOON IMMEDIATELY NE
   OF THE DEEPENING LEE CYCLONE...FROM ERN WY INTO THE NW NEB
   PANHANDLE.  THOUGH MOISTURE WILL BE LIMITED...DEEP MIXING/STEEP
   LOW-LEVEL LAPSE RATES COULD SUPPORT WEAK SURFACE-BASED BUOYANCY AND
   SOME RISK FOR STRONG WIND GUSTS.  MARGINALLY SEVERE HAIL WILL ALSO
   BE POSSIBLE WITH LOW-END SUPERCELL STRUCTURES...GIVEN EFFECTIVE BULK
   SHEAR AOA 40 KT BY THIS EVENING.

   ...NRN VA/MD TO DE AREA THIS AFTERNOON...
   THOUGH LOW-LEVEL MOISTURE WILL BE LIMITED...STRONG SURFACE
   HEATING/MIXING WILL CONTRIBUTE TO STEEP LOW-LEVEL LAPSE RATES IN
   ADVANCE OF A REINFORCING COLD FRONT MOVING SEWD FROM OH/NW PA. 
   WEAK/SHALLOW BUOYANCY WILL BE POSSIBLE ALONG THE FRONT IN AN
   ENVIRONMENT WITH STRONG WNWLY UNIDIRECTIONAL FLOW...SUCH THAT
   ISOLATED STRONG OUTFLOW GUSTS WILL BE POSSIBLE WITH SHALLOW
   CONVECTION.

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