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Mesoscale Discussion 379
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   MESOSCALE DISCUSSION 0379
   NWS STORM PREDICTION CENTER NORMAN OK
   0152 PM CDT SUN APR 19 2015

   AREAS AFFECTED...SOUTHWEST AR...WESTERN LA...EAST TX INCLUDING THE
   UPPER TX COAST

   CONCERNING...SEVERE POTENTIAL...WATCH LIKELY 

   VALID 191852Z - 191945Z

   PROBABILITY OF WATCH ISSUANCE...80 PERCENT

   SUMMARY...ISOLATED TO WIDELY SCATTERED STORMS WILL DEVELOP BY 21Z
   AHEAD OF A COLD FRONT ACROSS EAST TEXAS. THESE STORMS WILL TRACK
   EAST TOWARD THE UPPER TX COAST AND WESTERN LA. LARGE HAIL AND STRONG
   WINDS WILL BE THE MAIN THREATS...BUT A TORNADO OR TWO CANNOT BE
   RULED OUT. THE AREA IS BEING MONITORED FOR WATCH ISSUANCE BY 21Z.

   DISCUSSION...TEMPERATURES HAVE WARMED TO THE UPPER 70S TO LOW 80S
   FROM THE UPPER TX COAST TOWARD THE ARKLATEX/SABINE VALLEY...WITH
   DEWPOINTS FROM THE MID/UPPER 60S ACROSS SOUTHERN PORTIONS OF THE MCD
   AREA TO THE LOW 60S FURTHER NORTH. 18Z MESOANALYSIS AND FORECAST RAP
   SOUNDINGS SUGGEST SOME CAPPING STILL EXISTS ACROSS THE AREA BUT
   SHOULD ERODE BY AROUND 20-21Z. ONCE THIS OCCURS...STRONG SURFACE
   BASED INSTABILITY WILL LEAD TO THUNDERSTORM DEVELOPMENT NEAR/JUST
   AHEAD OF THE COLD FRONT. FORCING FOR ASCENT IS NOT AS STRONG AS
   FURTHER NORTH CLOSER TO THE UPPER TROUGH...BUT ISOLATED TO WIDELY
   SCATTERED SUPERCELLS WILL BE POSSIBLE. STORMS MAY REMAIN
   SEMI-DISCRETE AT FIRST BEFORE TRANSITIONING TOWARD BOWING SEGMENTS.
   STEEP MIDLEVEL LAPSE RATES AND EFFECTIVE SHEAR NEAR 35 KT WILL
   SUPPORT ROTATING UPDRAFTS AND LARGE HAIL WILL BE POSSIBLE.
   FURTHERMORE...DCAPE VALUES AOA 1200 J/KG AND SOME DRIER MIDLEVEL AIR
   COULD RESULT IN SOME STRONG/LOCALLY DAMAGING WINDS WITH THE
   STRONGEST STORMS. WHILE THE TORNADO THREAT SHOULD REMAIN
   LOW...MODEST LOW-LEVEL DIRECTIONAL SHEAR EXISTS ACROSS THIS
   AREA...WITH THE SHV VAD WIND PROFILE INDICATING 0-1KM SRH NEAR 100
   M2/S2. AS SUCH...ANY STORM THAT CAN REMAIN DISCRETE COULD POSE A
   BRIEF TORNADO THREAT.

   ..LEITMAN/HART.. 04/19/2015


   ATTN...WFO...LZK...LCH...SHV...HGX...FWD...EWX...

   LAT...LON   30459248 31319202 32029208 32839242 33519307 33809396
               33779498 32799520 31999553 31269604 29919751 29639758
               29369746 29159717 29059673 28959602 29179471 30029317
               30459248 

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Page last modified: April 19, 2015
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