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Mesoscale Discussion 1638
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   MESOSCALE DISCUSSION 1638
   NWS STORM PREDICTION CENTER NORMAN OK
   1245 PM CDT SAT AUG 30 2014

   AREAS AFFECTED...MUCH OF LOWER MI...NRN INDIANA...NERN IL

   CONCERNING...SEVERE POTENTIAL...WATCH POSSIBLE 

   VALID 301745Z - 302015Z

   PROBABILITY OF WATCH ISSUANCE...40 PERCENT

   SUMMARY...THE RISK FOR SEVERE THUNDERSTORMS WILL INCREASE THROUGH
   THE AFTERNOON. CONVECTIVE TRENDS WILL CONTINUE TO BE MONITORED...AND
   THE ISSUANCE OF A SEVERE THUNDERSTORM WATCH IS POSSIBLE.

   DISCUSSION...SFC OBSERVATIONS DEPICT A MOIST BOUNDARY LAYER ACROSS
   THE REGION...WITH DEWPOINTS IN THE UPPER 60S/LOWER 70S. AND...WITH
   THE TRANSLUCENT NATURE OF MID/HIGH CLOUDS AND BREAKS IN THE CLOUD
   COVERAGE PERMITTING PARTIAL INSOLATION...MLCAPE VALUES HAVE
   INCREASED TO 1000-1500 J/KG DESPITE RELATIVELY POOR MID-LEVEL LAPSE
   RATES. MEANWHILE...VISIBLE SATELLITE IMAGERY AND 7-KM CAPPI RADAR
   DATA INDICATE THAT CONVECTION IS INCREASING ON AN ISOLATED BASIS IN
   ADVANCE OF A MID-LEVEL CYCLONIC PERTURBATION CROSSING ERN WI INTO
   LAKE MI PER MOISTURE-CHANNEL IMAGERY. CONTINUED DIURNAL
   DESTABILIZATION COUPLED WITH MODESTLY INCREASING DCVA MAY CONTINUE
   TO BREED AN UPTICK IN CONVECTIVE COVERAGE/INTENSITY. THIS WOULD
   ESPECIALLY BE THE CASE ACROSS LOWER MI...WHICH WILL BE IN CLOSER
   PROXIMITY TO MORE ROBUST MID-LEVEL HEIGHT FALLS. HOWEVER...A
   CONFLUENCE AXIS TRAILING S OF SFC LOW PRESSURE EMERGING OVER NRN
   LAKE MI COULD ALSO BE A FOCUS FOR ISOLATED THUNDERSTORM DEVELOPMENT
   INTO NRN INDIANA WHERE SFC-3-KM LAPSE RATES ARE RELATIVELY STEEPER.

   THE PRESENCE OF 25-40 KT OF EFFECTIVE BULK SHEAR SHOULD ENCOURAGE
   CONVECTIVE ORGANIZATION INTO MULTICELL CLUSTERS...AND PERHAPS
   SUPPORT ONE OR TWO TRANSIENT/MARGINAL SUPERCELLS. DMGG WIND GUSTS
   SHOULD BE THE PRIMARY SVR RISK...WITH 25-40-KT SWLYS IN THE 1-3-KM
   LAYER AS SAMPLED BY AREA VWPS AND THE 18Z DETROIT RAOB BOLSTERING
   CONVECTIVE MOMENTUM TRANSPORT. MARGINALLY SVR HAIL...AND POSSIBLY A
   WEAK TORNADO...CANNOT BE RULED OUT WITH MORE SUSTAINED...
   DISCRETE/SEMI-DISCRETE CONVECTION. AT THIS TIME...THE PRIMARY
   UNCERTAINTY IS WITH REGARDS TO THE COVERAGE OF THE SVR
   RISK...WITHOUT STEEPER MID-LEVEL LAPSE RATES AND A SOMEWHAT
   DISORGANIZED APPEARANCE TO THE UPSTREAM MID-LEVEL DISTURBANCE PER
   WATER VAPOR LOOPS. REGARDLESS...CONVECTIVE TRENDS WILL CONTINUE TO
   BE MONITORED.

   ..COHEN/HART.. 08/30/2014


   ATTN...WFO...DTX...APX...IWX...GRR...LOT...

   LAT...LON   42728367 41398541 40648735 40698850 41098858 42078732
               43188660 44368625 45438546 45758457 45018328 43808296
               42728367 

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Page last modified: August 30, 2014
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