SPC AC 261241

   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   0741 AM CDT SAT SEP 26 2015

   VALID 261300Z - 271200Z

   ...NO SVR TSTM AREAS FORECAST...

   ...SUMMARY...
   THUNDERSTORMS WILL BE POSSIBLE THIS AFTERNOON ACROSS PARTS OF THE
   SOUTHERN PLAINS AND WESTERN GULF COASTAL REGION...AS WELL AS FROM
   FLORIDA TO THE EASTERN CAROLINAS.

   ...SYNOPSIS...
   IN MID/UPPER LEVELS...DOMINANT PATTERN FEATURES WILL REMAIN RIDGING
   FROM SWRN DESERTS TO NRN PLAINS AND LARGE AREA OF RELATIVELY LOW
   HEIGHTS OVER CENTRAL/SRN CONUS.  HEIGHTS ARE FCST TO FALL ACROSS
   MUCH OF PAC NW...NRN ROCKIES AND NRN PLAINS...AS SWLY FLOW ALOFT
   SHIFTS EWD AND INTENSIFIES WITH PROGRESSION OF SEVERAL POSITIVELY
   TILTED SHORTWAVES ACROSS WRN CANADA.  FARTHER SE...MID/UPPER-LEVEL
   LOW -- NOW EVIDENT IN MOISTURE-CHANNEL IMAGERY OVER ERN TN -- IS
   FCST TO WEAKEN THROUGH 12Z AS IT DRIFTS GENERALLY NWD ACROSS ERN KY
   TOWARD SRN OH.  MEANWHILE...SMALLER LOW/VORTICITY MAX ALOFT --
   CURRENTLY LOCATED INVOF NWRN OK/SWRN KS BORDER -- LIKEWISE IS
   EXPECTED TO WEAKEN...WHILE MOVING SSWWD ACROSS TX PANHANDLE.  THIS
   FEATURE ALSO WILL BECOME ENVELOPED IN BROAD/CYCLONIC FLOW FIELD
   ASSOCIATED WITH SLOWLY ORGANIZING MID/UPPER-LEVEL CYCLONE OVER TX
   COAST. 

   SFC FEATURES WERE MOSTLY WEAK AND DIFFUSE ACROSS CONUS AS OF
   11Z...WHICH IS NOT SURPRISING GIVEN UPPER PATTERN DESCRIBED ABOVE. 
   WEAK TROUGHING WAS EVIDENT FROM ERN MT SSEWD ACROSS CENTRAL/SRN HIGH
   PLAINS TO PERMIAN BASIN AND COAHUILA...GENERALLY 100-200 NM W OF
   MOIST AXIS LOCATED FROM NWRN ND ACROSS CENTRAL NEB TO N-CENTRAL TX
   AND CHARACTERIZED BY SPOTTY DEW POINTS LOW 60S F.  QUASISTATIONARY/
   FRONTOLYTIC BAROCLINIC ZONE WAS EVIDENT PARALLEL TO AND OFFSHORE
   ATLC COAST FROM NC TO GA...THEN SWWD ACROSS N-CENTRAL FL TO
   N-CENTRAL GULF.  

   ISOLATED TO SCATTERED TSTMS ARE EXPECTED TODAY OVER SRN ATLC COAST
   STATES...FL...W GULF COASTAL PLAIN...AND SRN HIGH PLAINS.  SEVERAL
   CRUCIAL LIMITING FACTORS PRECLUDE ENOUGH UNCONDITIONAL SVR
   PROBABILITIES FOR MRGL OUTLOOK AREA ATTM AS DESCRIBED BELOW...THOUGH
   STG TSTMS CANNOT BE RULED OUT IN A COUPLE OF REGIONS.  

   ...SRN HIGH PLAINS...
   A FEW STG TSTMS WITH GUSTY WINDS AND SMALL HAIL APCHG SVR LIMITS MAY
   OCCUR PRIMARILY THIS AFTN INTO EARLY EVENING FROM SRN TX PANHANDLE
   AND SOUTH PLAINS SWD TOWARD I-20 MAF-ABI CORRIDOR.  SPECIFIC FOCI
   APPEAR RATHER NEBULOUS...HOWEVER SFC DIABATIC HEATING...
   DIFFERENTIAL-HEATING ZONES FROM ANTECEDENT CLOUDS...AND SUBTLE
   CONVERGENCE INVOF SFC TROUGH SHOULD WEAKEN MLCINH SUBSTANTIALLY IN
   SUPPORT OF CONVECTIVE DEVELOPMENT.  MODES SHOULD BE MOSTLY
   MULTICELLULAR...BUT MAY BE WELL-VENTILATED ALOFT GIVEN
   MERIDIONAL/50-65-KT 250-MB JETLET EXPECTED BY 00Z FROM WRN TX
   PANHANDLE SWD ACROSS BIG BEND REGION.  STG DIRECTIONAL SHEAR
   ELONGATES 0-3-KM HODOGRAPHS IN FCST SOUNDINGS...AND VERY
   DEVIANT/SWWD MOTIONS OFF THOSE HODOGRAPHS MAY YIELD ENOUGH SRH TO
   SUPPORT TRANSIENT STORM ROTATION.  HOWEVER...0-1-KM SRH LOOKS TO BE
   VERY SMALL GIVEN WEAK SPEEDS.  LACK OF MORE ROBUST MOISTURE/THETAE
   AS WELL AS WEAK LOW-LEVEL FORCING SHOULD MITIGATE SVR POTENTIAL.

   ...S TX...
   SCATTERED MULTICELLULAR TSTMS SHOULD DEVELOP THIS AFTN IN REGIME OF
   RELATIVELY RICH BOUNDARY-LAYER MOISTURE AND FAVORABLE DIABATIC SFC
   HEATING.  WELL-MIXED SUBCLOUD LAYERS MAY SUPPORT STG GUSTS FROM SOME
   OF THIS CONVECTION.  DESPITE COOL 500-MB TEMPS -9 TO -11 DEG
   C...MIDDLE/UPPER-LEVEL LAPSE RATES WILL NOT BE PARTICULARLY
   STG...GENERALLY AROUND 6-6.5 DEG C/KM.  STILL...MLCAPE AROUND
   1000-1500 J/KG IS POSSIBLE.  WEAK DEEP-TROPOSPHERIC WINDS AND LACK
   OF SHEAR WILL LIMIT ANY POTENTIAL FOR MORE THAN BRIEF/TRANSIENT
   GUSTS OR HAIL APCHG SVR LIMITS.

   ..EDWARDS/ROGERS.. 09/26/2015

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