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Mesoscale Discussion 1815
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   MESOSCALE DISCUSSION 1815
   NWS STORM PREDICTION CENTER NORMAN OK
   0249 PM CDT MON OCT 06 2014

   AREAS AFFECTED...IL...IN...KY...TN

   CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE 

   VALID 061949Z - 062045Z

   PROBABILITY OF WATCH ISSUANCE...40 PERCENT

   SUMMARY...THE CHANCE FOR A FEW STRONG TO POSSIBLY SEVERE STORMS WILL
   EXIST OVER PORTIONS OF THE LOWER OH VALLEY SOUTH ACROSS WESTERN TN
   OVER THE NEXT COUPLE OF HOURS. STRONG WINDS AND SOME HAIL APPEAR TO
   BE THE PRIMARY HAZARDS.

   DISCUSSION...SEVERAL CLUSTERS AND WEAKLY ORGANIZED LINES OF STORMS
   HAVE BEEN DEVELOPING FROM SOUTHERN IL TO WEST-CENTRAL KY LATE THIS
   AFTERNOON AMIDST GENERALLY WEAK INSTABILITY. THIS ACTIVITY WAS
   DEVELOPING IN RESPONSE TO DIURNAL HEATING AND DEEP-LAYER ASCENT
   AHEAD OF A STRONG SHORTWAVE IMPULSE DIGGING INTO THE BASE OF AN
   EXPANSIVE LARGER-SCALE TROUGH FROM THE SOUTHERN CANADA AND THE GREAT
   LAKES SOUTH TO THE LOWER MS VALLEY. COLD AIR ALOFT AND SURFACE
   WARMING HAVE CONTRIBUTED TO STEEPENING LAPSE RATES WHILE MARGINAL
   BUT SUFFICIENT BOUNDARY LAYER MOISTURE WAS SUPPORTING NARROW
   CORRIDORS WHERE MLCAPE HAS CLIMBED TO AROUND 300-600 J/KG. STRONGER
   LOW-LEVEL CONVERGENCE AIDING STORM INITIATION AND PERHAPS STORM
   PERSISTENCE APPEARS TO BE MOST CONCENTRATED WITHIN TWO GENERAL
   AREAS...1) NEAR/ALONG THE COLD FRONT DEVELOPING ACROSS SOUTHERN IL
   AND IND...AND WITHIN A WEAK PRE-FRONTAL TROUGH EXTENDING FROM
   NORTHEAST KY SOUTHWESTWARD ACROSS WEST-CENTRAL KY AND WESTERN TN.
   EFFECTIVE SHEAR MAGNITUDES ACROSS THESE AREAS WERE IN THE RANGE OF
   35-40KT...PRIMARILY A RESULT OF STRONG CYCLONIC MID-LEVEL FLOW.
   WHILE ORGANIZED STORMS MAY BRIEFLY REACH SEVERE LEVELS WITH HAIL
   NEAR AN INCH IN DIAMETER AND WINDS PERHAPS APPROACHING 50KT...THERE
   REMAINS CONSIDERABLE UNCERTAINLY REGARDING LONGER-LIVED WIDESPREAD
   SEVERE POTENTIAL INTO THE EVENING HOURS GIVEN MOSTLY
   DIABATIC/DIURNAL INFLUENCE DRIVING THE CURRENT UPTICK IN CONVECTION.
   IF A CONTINUED INCREASE IN COVERAGE AND INTENSITY LASTS BEYOND THE
   NEXT HOUR...A WATCH IS POSSIBLE FROM PARTS OF WESTERN/CENTRAL KY
   SOUTHWEST INTO TN.

   ..CARBIN/HART.. 10/06/2014


   ATTN...WFO...JKL...ILN...LMK...OHX...IND...PAH...ILX...MEG...
   LSX...

   LAT...LON   39138752 39298634 39168508 38358362 37328419 35408703
               34909008 37018931 38268925 39138752 

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Page last modified: October 06, 2014
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