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Mesoscale Discussion 471
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   MESOSCALE DISCUSSION 0471
   NWS STORM PREDICTION CENTER NORMAN OK
   0135 AM CDT WED APR 27 2016

   AREAS AFFECTED...PORTIONS AR...NWRN LA...S-CENTRAL THROUGH NE TX.

   CONCERNING...SEVERE THUNDERSTORM WATCH 113...

   VALID 270635Z - 270830Z

   THE SEVERE WEATHER THREAT FOR SEVERE THUNDERSTORM WATCH 113
   CONTINUES.

   SUMMARY...EXTENSIVE SQUALL LINE FROM OZARKS ACROSS ARKLATEX TO
   PORTIONS S-CENTRAL/SW TX STILL POSES RISK OF SPORADIC DAMAGING GUSTS
   NEAR SVR LEVELS.  BRIEF/SMALL QLCS-TYPE TORNADO OR TWO CANNOT BE
   RULED OUT OVER NRN AR.  AREAS E OF WW 113 ACROSS AR ARE BEING
   MONITORED FOR POSSIBILITY OF ADDITIONAL WW AS CONVECTIVE/INSTABILITY
   TRENDS WARRANT.

   DISCUSSION...SFC MESOANALYSIS SHOWS OUTFLOW BOUNDARY FROM EARLIER
   MCS ARCHING FROM MEM AND SRC AREAS ACROSS NRN AR TO INTERSECTION
   WITH SQUALL LINE OVER BARRY COUNTY MO.  OUTFLOW BOUNDARY WILL REMAIN
   NEARLY STATIONARY...WITH ONLY MINOR NWD DRIFT POSSIBLE ON ITS WRN
   END BEFORE BEING OVERTAKEN BY CONVECTIVE BAND.  ALONG AND S OF
   OUTFLOW BOUNDARY...SFC DEW POINTS MID/UPPER 60S F OVER AR AND NE TX
   TREND TO LOW-MID 70S F OVER S TX.  BASED ON 00Z RAOBS AND FCST
   SOUNDINGS...EML-RELATED CINH IS STRONGER WITH SWWD EXTENT ACROSS
   TX...AND 06Z SHV RAOB SHOWS STG CINH WITH THAT LAYER WHOSE WARM AIR
   LIKELY IS ADVECTING POLEWARD TOWARD AR.  GRADUAL/NOCTURNAL DIABATIC
   COOLING IN FOREGOING WARM SECTOR...S OF OUTFLOW BOUNDARY...WILL
   CONTRIBUTE FURTHER TO SBCINH AS WELL.  FOR PAST 2-3 HOURS...MEASURED
   GUSTS HAVE BEEN SUB-SVR AT OBS SITES IN OK/AR/TX ACROSS WHICH SQUALL
   LINE HAS PASSED.  

   GIVEN THESE FACTORS...PRIND DAMAGING-WIND RISK GENERALLY WILL LESSEN
   WITH TIME EXCEPT WHERE SMALL-SCALE COLD-POOL PROCESSES MAY TRANSFER
   MOMENTUM GROUNDWARD.  STILL...FORCED ASCENT AND FAVORABLE BUOYANCY
   SHOULD PERMIT ORGANIZED BAND OF CONVECTION TO PERSIST FOR SEVERAL
   MORE HOURS...WITH SOME POTENTIAL THAT IT WILL BE NEAR SVR LEVELS
   WHEN IT GETS E OF WW OVER AR.  STEEP MIDLEVEL LAPSE RATES SUPPORT
   MUCAPE 2000-3000 J/KG OVER MUCH OF WARM SECTOR.  EFFECTIVE-SHEAR
   MAGNITUDES RANGE FROM 30-40 KT OVER NRN AR TO 50-60 KT OVER S
   TX...WITH NEARLY CONVECTION-PARALLEL MEAN-WIND VECTORS.  THIS WILL
   SUPPORT CONTINUED QLCS MODE FAVORING STG/ISOLATED SVR GUSTS WITH
   MRGL-SVR HAIL.  BRIEF TORNADO FROM QLCS LEADING-EDGE CIRCULATION
   STILL MAY BE POSSIBLE OVER NRN AR ESPECIALLY INVOF OUTFLOW BOUNDARY
   WHERE BACKED SFC FLOW AND ENHANCED LOW-LEVEL VORTICITY ARE PRESENT.

   ..EDWARDS.. 04/27/2016


   ATTN...WFO...MEG...JAN...LZK...LCH...SHV...TSA...HGX...FWD...
   EWX...SJT...

   LAT...LON   29790138 30449871 31269668 32859506 33989434 35619405
               36439382 36469130 35999125 34029164 33209199 32249275
               30959454 30009612 29459826 29539952 29790138 

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Page last modified: April 27, 2016
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