SPC AC 271648
   
   DAY 2 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   1148 AM CDT SAT APR 27 2013
   
   VALID 281200Z - 291200Z
   
   ...NO SVR TSTM AREAS FORECAST...
   
   ...SYNOPSIS...
   AN UPPER LEVEL SHORTWAVE TROUGH IS FORECAST TO SHIFT EWD ACROSS THE
   OH VALLEY ON SUNDAY. AS THIS OCCURS...IT WILL BECOME DISLOCATED FROM
   A POSITIVE TILT VORTICITY STREAMER EXTENDING SWWD INTO CNTRL TX AND
   NRN MEXICO. AT THE SURFACE...LOW PRESSURE WILL BE POSITIONED OVER
   THE LOWER/MID OH VALLEY AT THE START OF THE FORECAST PERIOD...WITH A
   COLD FRONT TRAILING TO THE SW INTO CNTRL LA AND THEN WWD INTO CNTRL
   TX. AS THE DAY PROGRESSES...THE LOW WILL WEAKEN AS IT LIFTS NEWD
   INTO OH...AND THE TRAILING COLD FRONT WILL DISSIPATE BY LATE
   AFTERNOON. MEANWHILE OVER THE NRN CONUS...A COLD FRONT ASSOCIATED
   WITH A SURFACE CYCLONE OVER CANADA WILL MOVE SWD ACROSS THE
   NRN/CNTRL PLAINS...AND WILL SERVE AS A FOCUS FOR THUNDERSTORM
   DEVELOPMENT DURING THE AFTERNOON AND NIGHT.
   
   ...SRN HIGH PLAINS...
   SELY LOW-LEVEL WINDS OVER MUCH OF TX WILL ENCOUNTER SWLY FLOW OVER
   THE SRN HIGH PLAINS SUNDAY AFTERNOON...AND WILL RESULT IN A WEAK
   ZONE OF SURFACE CONFLUENCE ORIENTED SWWD FROM WRN OK INTO W-CNTRL
   TX. DEWPOINTS IN THE 30S TO LOW 40S COMBINED WITH TEMPERATURES IN
   THE LOW 80S AND STEEP LOW TO MIDLEVEL LAPSE RATES WILL CONTRIBUTE
   TOWARD MLCAPE VALUES FROM 500-1500 J/KG ALONG AND E OF THE
   CONFLUENCE ZONE. THE UNSTABLE ENVIRONMENT COMBINED WITH A MINOR
   DISTURBANCE MOVING SWD INTO THE AREA DURING THE AFTERNOON MAY BE
   SUFFICIENT FOR ISOLATED TO SCATTERED THUNDERSTORM DEVELOPMENT.
   THOUGH VERTICAL WIND PROFILES WILL BE UNFAVORABLE FOR ORGANIZED
   THUNDERSTORM DEVELOPMENT...ISOLATED DAMAGING WIND GUSTS AND
   MARGINALLY SEVERE HAIL CANNOT BE RULED OUT.
   
   ...CNTRL/ERN KY...SRN OH...
   AS AN UPPER LEVEL SHORTWAVE TROUGH MOVES ENEWD ACROSS THE OH VALLEY
   DURING THE AFTERNOON...A MIDLEVEL DRYSLOT IS FORECAST TO SPREAD
   ACROSS CNTRL/ERN KY AND SRN OH. ANY CLEARING THAT TAKES PLACE WOULD
   AID IN DESTABILIZING THE BOUNDARY LAYER...AND WITH 50S DEWPOINTS
   PRESENT ACROSS THE AREA...COULD POTENTIALLY BOOST MLCAPE VALUES TO
   500-1000 J/KG. ASCENT ASSOCIATED WITH THE UPPER DISTURBANCE COMBINED
   WITH WEAKENING SURFACE CONVERGENCE TRAILING A LOW OVER ERN IND/WRN
   OH MAY RESULT IN THE DEVELOPMENT OF A BROKEN LINE OF STORMS. LOW TO
   MIDLEVEL SWLY FLOW ON THE ORDER OF 20-40 KT WILL BE MARGINALLY
   FAVORABLE FOR ORGANIZED THUNDERSTORM DEVELOPMENT POSING A LOW-END
   THREAT FOR SEVERE WIND/HAIL.
   
   ...SERN STATES...
   THUNDERSTORMS ARE FORECAST TO BE ONGOING AT THE START OF THE PERIOD
   FROM MIDDLE TN SWD INTO PORTIONS OF MS/AL. MORNING FORECAST
   SOUNDINGS ACROSS THESE AREAS INDICATE SUFFICIENT CAPE AND VERTICAL
   WIND SHEAR WILL BE PRESENT FOR AN ISOLATED DAMAGING WIND THREAT.
   THEREAFTER...LAPSE RATES ARE EXPECTED TO WEAKEN SIGNIFICANTLY IN THE
   LOW AND MIDLEVELS. THOUGH SHOWERS AND THUNDERSTORMS WILL LIKELY
   CONTINUE THROUGH THE AFTERNOON...THE SEVERE WEATHER THREAT IS
   FORECAST TO BECOME INCREASINGLY MARGINAL.
   
   ...SRN TX...
   UNCERTAINTY EXISTS IN HOW MUCH RESIDUAL CLOUD COVER PRODUCED BY
   OVERNIGHT CONVECTION WILL EXIST OVER SRN TX ON SUNDAY. IF HEATING
   CAN OCCUR AND TEMPERATURES WARM INTO THE 80S...THEN LOW TO MID 60S
   DEWPOINTS WILL AID IN MLCAPE VALUES NEAR 1000 J/KG. ESELY WINDS
   OCCURRING OVER THE LOWEST 1 KM SURMOUNTED BY 30-40 KT WLY FLOW AT 6
   KM WILL RESULT IN LONG HODOGRAPHS FAVORABLE FOR SPLITTING STORMS.
   LATEST MODEL GUIDANCE INDICATES THUNDERSTORMS MAY MOVE EWD OUT OF
   MEXICO AND INTO SRN TX DURING THE AFTERNOON AND EVENING. IF THIS
   SCENARIO OCCURS...THEN ISOLATED LARGE HAIL WOULD BE POSSIBLE.
   
   ..GARNER.. 04/27/2013
   
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