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Mesoscale Discussion 1733
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   MESOSCALE DISCUSSION 1733
   NWS STORM PREDICTION CENTER NORMAN OK
   0619 PM CDT FRI SEP 19 2014

   AREAS AFFECTED...CNTRL/NERN NEB...SERN SD...CNTRL/NWRN IA...SRN MN

   CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY 

   VALID 192319Z - 200145Z

   PROBABILITY OF WATCH ISSUANCE...20 PERCENT

   SUMMARY...THE AREA IS BEING MONITORED FOR THUNDERSTORM DEVELOPMENT
   THIS EVENING...ALONG WITH SOME SVR RISK. CONVECTIVE TRENDS WILL
   CONTINUE TO BE MONITORED...THOUGH WW ISSUANCE IS CURRENTLY UNLIKELY.

   DISCUSSION...SFC OBSERVATIONS REVEAL A WIND-SHIFT AXIS EXTENDING
   FROM A DIFFERENTIAL-HEATING INDUCED BAROCLINIC ZONE LYING W-E ACROSS
   SRN MN...SWWD INTO SERN SD AND FARTHER SW THROUGH CNTRL NEB.
   SFC-3-KM LAPSE RATES OF 8-9 C/KM EXTEND NEWD FROM THE CNTRL HIGH
   PLAINS INTO CNTRL NEB...IN PROXIMITY TO THE WIND-SHIFT AXIS. AT THE
   LEADING EDGE OF DEEP MIXING ASSOCIATED WITH THESE LAPSE
   RATES...WHERE SFC TEMPERATURES HAVE BREACHED 90F IN SOME AREAS...VIS
   IMAGERY INDICATES A WEAK-CONVERGENCE-MANIFESTED NARROW BAND OF
   TOWERING CU. RELATIVELY REDUCED MLCINH OWING TO ANTECEDENT DIABATIC
   SFC-LAYER HEATING MAY ALLOW FOR DEEPER CONVECTION TO BLOSSOM FROM
   THIS CLOUD BAND IN THE NEXT FEW HOURS. HOWEVER...CAPPING ASSOCIATED
   WITH AN EML THAT HAS OVERSPREAD THE AREA MAY MITIGATE THE POTENTIAL
   FOR SFC-BASED CONVECTIVE DEVELOPMENT. STORMS MAY NOT MATERIALIZE
   UNTIL LATER THIS EVENING TOWARD THE UPPER MS VALLEY...AS MODEST
   COOLING ALOFT OCCURS IN CONCERT WITH SLIGHT AMPLIFICATION TO THE
   MID/UPPER-LEVEL FLOW...THOUGH NOCTURNAL STABILIZATION OF THE PBL MAY
   MITIGATE THE OVERALL SVR-TSTM POTENTIAL.

   REGARDLESS...THE PRESENCE OF 1500-3000 J/KG OF MLCAPE ASSOCIATED
   WITH STEEP...EML-RELATED MID-LEVEL LAPSE RATES OVERLYING
   LOWER/MIDDLE 60S SFC DEWPOINTS E OF THE WIND-SHIFT AXIS BREEDS SOME
   CONDITIONAL SUPPORT FOR A SVR-TSTM RISK. IF THUNDERSTORMS WERE TO
   FORM...AMPLE DEEP SHEAR ASSOCIATED WITH 30-50-KT MID-LEVEL WLYS
   SAMPLED BY AREA VWPS COULD SUPPORT ORGANIZED/SUSTAINED CONVECTION
   WITH AT LEAST ISOLATED INSTANCES OF SVR HAIL/WIND.
   ULTIMATELY...THERE IS LARGE UNCERTAINTY IN THE POTENTIAL FOR
   SFC-BASED/SVR CONVECTION OWING TO THE LACK OF STRONGER DEEP-LAYER
   FORCING FOR ASCENT AND THE ANTECEDENT CAPPING. AS SUCH...CONVECTIVE
   TRENDS WILL CONTINUE TO BE MONITORED.

   ..COHEN/GOSS.. 09/19/2014


   ATTN...WFO...MPX...DMX...FSD...OAX...GID...LBF...

   LAT...LON   41200023 41480038 42049943 44109511 44179310 42899303
               41849500 41179890 41200023 

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Page last modified: September 20, 2014
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