SPC AC 070555

   DAY 1 CONVECTIVE OUTLOOK  
   NWS STORM PREDICTION CENTER NORMAN OK
   1255 AM CDT TUE APR 07 2015

   VALID 071200Z - 081200Z

   ...THERE IS A MRGL RISK OF SVR TSTMS FROM THE SOUTH-CENTRAL
   PLAINS/LOWER MO VALLEY TO THE MIDWEST/SOUTHERN APPALACHIANS...

   ...THERE IS A MRGL RISK OF SVR TSTMS ACROSS PORTIONS OF
   NORTHERN/CENTRAL CA...

   ...SUMMARY...
   ISOLATED STRONG TO SEVERE THUNDERSTORMS WILL BE POSSIBLE TODAY
   ACROSS PORTIONS OF THE MIDWEST TO THE SOUTHERN APPALACHIANS...WITH
   OTHER SEVERE THUNDERSTORMS POSSIBLE ACROSS THE LOWER MISSOURI VALLEY
   AND POSSIBLY INTERIOR NORTHERN/CENTRAL CALIFORNIA.

   ...SYNOPSIS...
   A DEGREE OF LARGE-SCALE PATTERN AMPLIFICATION IS EXPECTED DURING THE
   PERIOD...WITH PREVALENT LOWER-AMPLITUDE WEST-SOUTHWESTERLY
   MID/HIGHER-LEVEL FLOW TO THE EAST OF AN EASTWARD-MOVING UPPER TROUGH
   OVER CA/NV. WEAK SURFACE LOW DEVELOPMENT/MIGRATION IS EXPECTED
   ACROSS KS/LOWER MO VALLEY TODAY IN VICINITY OF A WAVY WEST-EAST
   FRONT FROM THE CENTRAL PLAINS TO THE MIDWEST. A DRYLINE WILL EXTEND
   SOUTH-SOUTHWESTWARD FROM A SOUTH-CENTRAL/EAST-CENTRAL KS TRIPLE
   POINT INTO WESTERN OK AND WEST/SOUTHWEST TX.

   ...MIDWEST/LOWER OH VALLEY TO SOUTHERN APPALACHIANS...
   NEAR THE TERMINUS OF A WEST-SOUTHWESTERLY LOW-LEVEL JET AND RELATED
   WARM-ADVECTION REGIME...CLUSTERS OF SHOWERS/THUNDERSTORMS ARE LIKELY
   TO BE ONGOING ACROSS PORTIONS OF THE REGION THIS MORNING. WITHIN A
   BELT OF MODERATELY STRONG MID-LEVEL WINDS AND POSSIBLY AIDED BY AN
   EMBEDDED MCV...THESE STORMS MAY GENERALLY PERSIST
   EAST-SOUTHEASTWARD/POSSIBLY GROW UPSCALE THROUGH THE DAY ACROSS THE
   LOWER OH VALLEY AND TOWARD THE SOUTHERN APPALACHIANS. PERIPHERAL TO
   EARLY DAY CLOUD COVER/STORMS...SUFFICIENT HEATING/DESTABILIZATION
   MAY CONTRIBUTE TO AN INCREASE IN THUNDERSTORM COVERAGE/INTENSITY BY
   AFTERNOON. EPISODIC BOUTS OF SEVERE HAIL AND LOCALLY GUSTY WINDS
   APPEAR POSSIBLE.

   ELSEWHERE ACROSS THE MIDWEST/UPPER MS VALLEY...A SOMEWHAT SEPARATE
   CORRIDOR OF MOSTLY ELEVATED THUNDERSTORM DEVELOPMENT COULD OCCUR
   TODAY VIA A WARM-AIR ADVECTION REGIME FOCUSED TO THE NORTH OF THE
   WEST-EAST FRONT ACROSS NORTHERN MO AND IL/INDIANA. AMPLE ELEVATED
   BUOYANCY/VERY STEEP MID-LEVEL LAPSE RATES COULD RESULT IN ISOLATED
   LARGE HAIL FOR AREAS POTENTIALLY INCLUDING EASTERN IA/NORTHERN IL.

   ...LOWER MO VALLEY/SOUTH-CENTRAL PLAINS...
   THERE IS AT LEAST A CONDITIONAL RISK FOR SURFACE-BASED SEVERE
   THUNDERSTORM DEVELOPMENT LATE THIS AFTERNOON/EVENING NEAR THE
   SURFACE TRIPLE POINT AND NEARBY DRYLINE AND FRONT EXTENDING ACROSS
   THE LOWER MO VALLEY. LARGE-SCALE INFLUENCES WILL BE WEAK...BUT
   SUFFICIENT HEATING/MASS CONVERGENCE COULD ALLOW FOR ISOLATED DEEP
   CONVECTIVE DEVELOPMENT ACROSS AREAS INCLUDING SOUTHEAST KS/WESTERN
   MO. IN THE PRESENCE OF VERY STEEP LAPSE RATES/STRONG BUOYANCY AND
   AROUND 40 KT OF EFFECTIVE SHEAR...ISOLATED SUPERCELLS CAPABLE OF
   LARGE HAIL...LOCALLY STRONG WINDS...AND A TORNADO /ALBEIT MODEST
   LOW-LEVEL WINDS/ WOULD BE POSSIBLE CONTINGENT UPON THE SUSTENANCE OF
   DEEPER CONVECTION.

   ...SOUTHERN HIGH PLAINS...
   THE LIKELIHOOD/POTENTIAL COVERAGE OF THUNDERSTORM DEVELOPMENT IN THE
   VICINITY OF THE DRYLINE LATE THIS AFTERNOON/EARLY EVENING REMAINS
   UNCERTAIN...BUT AT MOST...ONLY VERY ISOLATED THUNDERSTORMS ARE
   ANTICIPATED. FACTORS SUCH AS WEAK LARGE-SCALE INFLUENCES AND SOME
   MID-LEVEL WARMING/HEIGHT RISES SINCE MONDAY...ALONG WITH
   ANTICIPATIONS OF WEAKER MASS CONVERGENCE/CONFLUENCE NEAR THE
   DRYLINE...CASTS DOUBT ON CONSEQUENTIAL DEEP CONVECTIVE DEVELOPMENT.
   SHOULD STORMS DEVELOP/REMAIN SUSTAINED...MODERATE TO STRONG BUOYANCY
   AND 30-40 KT OF EFFECTIVE SHEAR COULD RESULT IN A HIGH-BASED
   SUPERCELL/LARGE HAIL RISK. SEVERE POTENTIAL CURRENTLY APPEARS TOO
   SPECULATIVE FOR PROBABILITIES AT THIS JUNCTURE...BUT THIS SCENARIO
   WILL BE REEVALUATED IN SUBSEQUENT OUTLOOK UPDATES.

   ...NORTHERN/CENTRAL CA SACRAMENTO/SAN JOAQUIN VALLEYS...
   THE OFFSHORE UPPER LOW WILL GRADUALLY SPREAD INLAND/
   EAST-SOUTHEASTWARD OVER NORTH-CENTRAL CA AND NV TODAY. LAPSE RATES
   WILL STEEPEN THIS AFTERNOON IN THE WAKE OF THE COLD FRONT. ALTHOUGH
   OVERALL MOISTURE CONTENT WILL BE LIMITED /LOWER 40S F DEWPOINTS AT
   MOST/ AND CLOUD COVER MAY LINGER...SUFFICIENT /ALBEIT WEAK/
   DESTABILIZATION MAY OCCUR THIS AFTERNOON ACROSS PORTIONS OF THE
   SACRAMENTO/SAN JOAQUIN VALLEYS TO ALLOW FOR SOME STRONGER STORMS
   CAPABLE OF MAINLY SMALL HAIL.

   ..GUYER/GLEASON.. 04/07/2015

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