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Mesoscale Discussion 2159
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   MESOSCALE DISCUSSION 2159
   NWS STORM PREDICTION CENTER NORMAN OK
   0500 PM CDT SUN SEP 11 2011
   
   AREAS AFFECTED...MIDDLE/WRN TN...CNTRL/NRN MS...PARTS OF CNTRL/NRN
   AL...NERN LA...EXTREME SERN AR
   
   CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY 
   
   VALID 112200Z - 112330Z
   
   A FEW STORMS COULD PRODUCE STRONG WIND GUSTS INTO EARLY EVENING.
   WITH ONLY A MINIMAL SVR THREAT...THE ISSUANCE OF A WW IS UNLIKELY.
   
   LATE AFTERNOON MESOANALYSIS DEPICTS A SFC TROUGH AXIS EXTENDING
   ACROSS THE MID-SOUTH INTO THE LOWER MS VALLEY. THIS FEATURE EXHIBITS
   CHARACTERISTICS OF A DRYLINE NEAR AND SOUTH OF THE GREENVILLE MS
   AREA...WHERE IT SEPARATES THE HOTTER/DEEPLY MIXED BOUNDARY LAYER TO
   THE WEST FROM MODESTLY RICHER LOW-LEVEL MOISTURE TO THE EAST. THIS
   MOISTURE...SUPPORTING MLCAPE VALUES OF 1000-1500 J/KG...WILL COMBINE
   WITH SUFFICIENT SFC CONVERGENCE TO SUPPORT ISOLATED TO SCATTERED
   THUNDERSTORMS INTO EARLY EVENING. THE GREATEST CONVECTIVE COVERAGE
   IS ANTICIPATED ALONG AND NORTH OF THE HIGHWAY 82 CORRIDOR...WHERE
   ASCENT OFFERED BY TWO SUBTLE MID-LEVEL IMPULSES PIVOTING AROUND THE
   LARGER-SCALE PV MAX WILL AUGMENT DIURNALLY ENHANCED BOUNDARY-LAYER
   CIRCULATIONS AND SFC CONVERGENCE ALONG THE TROUGH/DRYLINE. FARTHER
   SOUTH...CONVECTIVE COVERAGE WILL BE MORE SUPPRESSED TOWARD
   INTERSTATE 20...AS AMPLE DRY AIR ALOFT WRAPS AROUND THE SRN FRINGES
   OF THE PV MAX.
   
   ENHANCED MID/UPPER-LEVEL FLOW IN ASSOCIATION WITH A
   CYCLONICALLY-CURVED UPPER-LEVEL SPEED MAX OVER THE AREA IS
   SUPPORTING 25-30 KT OF EFFECTIVE BULK SHEAR SOUTH OF HIGHWAY
   82...WITH WEAKER MID-LEVEL FLOW/VERTICAL SHEAR FARTHER NORTH. AS
   SUCH...A FEW MULTICELLULAR CLUSTERS WILL BE POSSIBLE ACROSS PARTS OF
   CNTRL/NRN MS AND CNTRL AL...WITH MORE PULSE CONVECTION ELSEWHERE.
   STRONG WIND GUSTS AND SMALL HAIL WILL BE POSSIBLE WITH THE
   STRONGEST/MOST PERSISTENT STORMS UNTIL AFTER 01Z...WHEN DIABATIC
   COOLING COMMENCES. WHILE AN ISOLATED THREAT FOR A DMGG WIND GUST OR
   MARGINALLY SVR HAIL CANNOT BE RULED OUT...THE LACK OF STRONGER
   FORCING FOR ASCENT / GREATER INSTABILITY IS EXPECTED TO MITIGATE THE
   OVERALL SVR THREAT.
   
   ..COHEN.. 09/11/2011
   
   
   ATTN...WFO...MRX...OHX...BMX...HUN...MEG...JAN...
   
   LAT...LON   35138574 33148704 31659072 32219187 33549095 36018841
               36418627 35138574 
   
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Page last modified: September 11, 2011
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