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Mesoscale Discussion 139
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   MESOSCALE DISCUSSION 0139
   NWS STORM PREDICTION CENTER NORMAN OK
   0130 PM CDT WED MAR 25 2015

   AREAS AFFECTED...PORTIONS OF SRN MO AND NRN AR

   CONCERNING...SEVERE POTENTIAL...WATCH LIKELY 

   VALID 251830Z - 252030Z

   PROBABILITY OF WATCH ISSUANCE...95 PERCENT

   SUMMARY...THE RISK FOR SEVERE THUNDERSTORMS WITH LARGE
   HAIL...DAMAGING WINDS...AND POSSIBLY ONE OR TWO TORNADOES WILL
   INCREASE DURING THE NEXT FEW HOURS. A WW WILL LIKELY BE REQUIRED.

   DISCUSSION...RECENT SFC OBSERVATIONS INDICATE THE NWD RETURN OF
   MODESTLY RICH LOW-LEVEL MOISTURE...WITH SFC DEWPOINTS IN THE MIDDLE
   50S EXTENDING AS FAR N AS PARTS OF N-CNTRL AND NW AR. SIMILAR
   MOISTURE WILL CONTINUE TO ADVANCE NWD ACROSS THE OZARKS AND VICINITY
   INTO THE EVENING HOURS...AHEAD OF A TIGHTENING BAROCLINIC ZONE TO
   THE NW/N. THIS BAROCLINIC ZONE...AND RELATED SFC FRONT...WILL
   ADVANCE SEWD/SWD ACROSS THE DISCUSSION AREA INTO THE EVENING HOURS.
   IN THE MEANTIME...ONGOING CINH -- EVIDENT IN BILLOWS AND STANDING
   WAVE CLOUD FORMATIONS PER VIS IMAGERY -- WILL CONTINUE TO ERODE WITH
   INSOLATION-SUPPORTED DIABATIC SFC HEATING. FURTHERMORE...LARGE-SCALE
   ASCENT ATTENDANT TO AN UPSTREAM SHORTWAVE TROUGH CROSSING WRN OK AND
   WRN N TX WILL AFFECT THE REGION BY LATE AFTERNOON...WHILE
   DIFFERENTIAL HEATING ON THE SRN FRINGES OF ELEVATED CONVECTION
   ACROSS SWRN MO LOCALLY ENHANCES BAROCLINICITY.

   AS A RESULT OF THESE FACTORS...SFC-BASED CONVECTION WILL LIKELY
   DEVELOP ACROSS THE REGION IN THE 20Z-22Z TIME FRAME -- MAINLY ACROSS
   PARTS OF SRN MO -- AND SPREAD EWD/ESEWD. STORMS DEVELOPING FARTHER W
   ACROSS OK WILL MOVE INTO AND ACROSS AR LATE THIS AFTERNOON INTO THE
   EVENING.

   WITH H7-H5 LAPSE RATES AROUND 8.0-8.5 C/KM ABOVE THE AFOREMENTIONED
   MOISTURE...MLCAPE AROUND 1000-2500 J/KG WILL EXIST S OF THE SFC
   FRONT. GIVEN 45-60 KT OF EFFECTIVE BULK SHEAR...WITH VECTORS
   ORIENTED WITH A SUBSTANTIAL FRONT/BOUNDARY-PARALLEL
   COMPONENT...INTENSE CONVECTION WILL LIKELY EVOLVE INTO BOWING/LEWP
   SEGMENTS WITH LARGE HAIL AND DAMAGING WINDS. SOME TORNADO POTENTIAL
   CANNOT BE RULED OUT...ESPECIALLY IF ANY SUPERCELLS ARE SUSTAINED
   PROVIDED BACKED SFC FLOW ENHANCING LOW-LEVEL SRH. HOWEVER...OVERALL
   CONFIDENCE IN A PROLONGED TORNADO RISK MAY BE MITIGATED BY 
   /1/ POTENTIALLY UNFAVORABLE CONVECTIVE MODE.../2/ LACK OF MORE
   ROBUST BOUNDARY-LAYER MOISTURE RETURN...AND /3/ UNDERCUTTING NATURE
   OF THE CONVECTIVELY AUGMENTED SYNOPTIC FRONT.

   A MESOSCALE DISCUSSION FOR AREAS W OF THIS REGION IS FORTHCOMING
   SHORTLY.

   ..COHEN/BUNTING.. 03/25/2015


   ATTN...WFO...LZK...SGF...TSA...

   LAT...LON   36939464 37259337 36989170 35609153 35139282 35369427
               35949452 36939464 

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Page last modified: March 25, 2015
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