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Mesoscale Discussion 638
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   MESOSCALE DISCUSSION 0638
   NWS STORM PREDICTION CENTER NORMAN OK
   1256 PM CDT THU MAY 14 2015

   AREAS AFFECTED...PORTIONS OF CNTRL/SRN UT AND FAR NRN AZ

   CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY 

   VALID 141756Z - 142030Z

   PROBABILITY OF WATCH ISSUANCE...20 PERCENT

   SUMMARY...THE AREA IS BEING MONITORED FOR AN INCREASING RISK FOR
   ISOLATED SEVERE THUNDERSTORMS. WHILE WW ISSUANCE IS NOT CURRENTLY
   LIKELY...CONVECTIVE TRENDS WILL CONTINUE TO BE MONITORED FOR
   INCREASING SEVERE THUNDERSTORM POTENTIAL THROUGHOUT THE DAY.

   DISCUSSION...WATER VAPOR LOOPS IMPLY AN AREA OF ASCENT SPREADING
   NEWD FROM THE LOWER CO RIVER VALLEY WITHIN THE EXIT REGION OF A
   MID-LEVEL SPEED MAX EDGING INTO THE SWRN CONUS ON THE SRN RIM OF
   BROADER CYCLONIC FLOW. WITH AREAS OF INSOLATION SUCCEEDING THE
   PASSAGE OF EARLIER CONVECTION ACCOMPANYING A LEAD WAVE NOW
   PROGRESSING TOWARD THE CNTRL ROCKIES...TOWERING CUMULUS DEVELOPMENT
   AND ISOLATED TO WIDELY SCATTERED THUNDERSTORM ACTIVITY ARE NOW BEING
   NOTED NEAR THE AZ/UT BORDER. WITH INCREASING LARGE-SCALE ASCENT AND
   DIURNALLY STRENGTHENING OROGRAPHIC CIRCULATIONS...THUNDERSTORM
   COVERAGE SHOULD FURTHER INCREASE INTO THE AFTERNOON.

   THE PRESENCE OF 30-50 KT OF EFFECTIVE BULK SHEAR MAY FACILITATE 
   ORGANIZED/SUSTAINED CONVECTIVE STRUCTURES AND PERHAPS MARGINAL
   SUPERCELL STRUCTURES/BOWING SEGMENTS. HOWEVER...DESPITE RELATIVELY
   STEEP MID-LEVEL LAPSE RATES...GPS PW VALUES AROUND ONE-HALF INCH
   SUGGEST LIMITED TROPOSPHERIC MOISTURE CONTENT...AND OVERALL UPDRAFT
   MASS FLUXES ARE NOT EXPECTED TO BE PARTICULARLY ROBUST.
   FURTHERMORE...LIMITED LOW-LEVEL MOISTURE /SFC DEWPOINTS IN THE 30S
   TO 40S/ WILL MARGINALIZE SFC-BASED INSTABILITY. THESE FACTORS SHOULD
   MITIGATE THE OVERALL SVR RISK.

   REGARDLESS...THE DEVELOPMENT OF INVERTED-VEE THERMODYNAMIC PROFILES
   CHARACTERISTIC OF DEEP VERTICAL MIXING/ABUNDANT SUB-CLOUD
   EVAPORATIONAL COOLING WILL ENCOURAGE STRONG CONVECTIVE DOWNDRAFTS
   WITH SFC GUSTS POTENTIALLY NEARING/BECOMING MARGINALLY SVR ON AN
   ISOLATED BASIS. FURTHERMORE...THE ICX VWP SAMPLES AROUND 35-55 KT OF
   UNIDIRECTIONAL SLYS IN THE LOWER PORTION OF THE CLOUD
   LAYER...SUGGESTING THAT CONVECTIVE MOMENTUM TRANSPORT MAY ENHANCE
   SFC GUSTS. ISOLATED HAIL -- PERHAPS APPROACHING MARGINALLY SVR
   LEVELS -- CANNOT BE RULED OUT...THOUGH THE RELATIVE DEARTH OF
   MOISTURE SHOULD BE A MITIGATING FACTOR.

   ..COHEN/GUYER.. 05/14/2015


   ATTN...WFO...GJT...FGZ...SLC...VEF...

   LAT...LON   36741276 38221336 39801329 40221198 39561040 37950951
               36730976 36351158 36741276 

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Page last modified: May 14, 2015
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