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Mesoscale Discussion 480
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   MESOSCALE DISCUSSION 0480
   NWS STORM PREDICTION CENTER NORMAN OK
   0744 AM CDT MON APR 27 2015

   AREAS AFFECTED...CENTRAL/SOUTHERN LA AND FAR SOUTHERN MS

   CONCERNING...TORNADO WATCH 125...126...

   VALID 271244Z - 271415Z

   THE SEVERE WEATHER THREAT FOR TORNADO WATCH 125...126...CONTINUES.

   SUMMARY...A FAST-MOVING SQUALL LINE WILL CONTINUE TO POSE A DAMAGING
   WIND/SOME TORNADO RISK THIS MORNING ACROSS MUCH OF SOUTHERN/CENTRAL
   LA POTENTIALLY INTO FAR SOUTHWEST/SOUTHERN MS. TORNADO WATCH 126
   CONTINUES UNTIL 18Z. 

   PENDING SQUALL LINE TRENDS...A NEW WATCH MAY BE NEEDED FOR
   ADDITIONAL PORTIONS OF SOUTHEAST LA AND POSSIBLY FAR SOUTHERN MS BY
   MID-MORNING.

   DISCUSSION...A FAST-MOVING ASYMMETRIC SQUALL LINE WITH LEADING BOW
   AND NORTH-SIDE EMBEDDED COMMA HEAD CONTINUES TO QUICKLY /50+ KT/
   MOVE EASTWARD ACROSS SOUTH-CENTRAL LA AS OF 1230Z/730AM CDT. THIS
   SYSTEM REMAINS VERY WELL-BALANCED/ORGANIZED WITH VERY COLD CLOUD
   TOPS /ROUGHLY -80C/ AND A TIGHT LEADING-EDGE RADAR REFLECTIVITY
   GRADIENT. LOW-LEVEL STORM RELATIVE INFLOW REMAINS RELATIVELY STRONG
   AND RECENT WSR-88D VWP DATA FROM FORT POLK IS SAMPLING A VERY STRONG
   /60 KT BETWEEN 2-4 KM AGL/ REAR-INFLOW JET IN THE IMMEDIATE WAKE OF
   THE BOW ECHO. A PROXIMITY 12Z OBSERVED SOUNDING FROM LAKE CHARLES
   SAMPLED AROUND 2700 J/KG MLCAPE AND VERY STEEP MID-LEVEL LAPSE RATES
   /8.1 C PER KM BETWEEN 700-500 MB/ WITH VERY STRONG LOW-LEVEL
   SRH/DEEP-LAYER SHEAR...WITH A RELATIVELY SIMILAR LAPSE RATE/VERTICAL
   SHEAR PROFILE NOTED DOWNSTREAM PER THE 12Z SLIDELL OBSERVED
   SOUNDING. WHILE SOME BOUNDARY LAYER INHIBITION/MODEST LOW-LEVEL
   LAPSE RATES MAY BE SOMEWHAT MITIGATING MORE ROBUST
   DOWNDRAFTS...EMBEDDED POCKETS OF DAMAGING WINDS AND POSSIBLY A
   TORNADO WILL REMAIN CONCERNS THIS MORNING.

   ..GUYER.. 04/27/2015


   ATTN...WFO...MOB...JAN...LIX...LCH...SHV...

   LAT...LON   30659283 31359281 31489179 31419083 31208982 30678924
               29139023 29779315 30659283 

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Page last modified: April 27, 2015
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