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Mesoscale Discussion 1602
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   MESOSCALE DISCUSSION 1602
   NWS STORM PREDICTION CENTER NORMAN OK
   1118 AM CDT SAT AUG 23 2014

   AREAS AFFECTED...NRN AND EASTERN ILLINOIS INTO WRN INDIANA

   CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY 

   VALID 231618Z - 231815Z

   PROBABILITY OF WATCH ISSUANCE...20 PERCENT

   SUMMARY...IN ADDITION TO THE RISK FOR VERY HEAVY RAINFALL AND
   FREQUENT CLOUD TO GROUND LIGHTNING...THE POTENTIAL FOR STRONG WIND
   GUSTS MAY BEGIN TO INCREASE WITH STORMS OVERSPREADING THE REGION
   THIS AFTERNOON.  THE PROBABILITY OF A SEVERE WEATHER WATCH ISSUANCE
   STILL SEEMS LOW...BUT TRENDS IN STORM COVERAGE AND ORGANIZATION WILL
   CONTINUE TO BE MONITORED.

   DISCUSSION...VIGOROUS CONVECTION PERSISTS WITH A BAND OF FORCING FOR
   UPWARD VERTICAL MOTION ASSOCIATED WITH A WEAK SHORT WAVE IMPULSE NOW
   PROGRESSING AROUND/THROUGH THE CREST OF MID-LEVEL RIDGING ACROSS
   NORTHERN ILLINOIS AND SOUTHERN WISCONSIN.  A LINE OF THUNDERSTORMS
   APPEARS LIKELY TO CONTINUE SPREADING EASTWARD INTO THE CHICAGO
   METROPOLITAN AREA THROUGH THE 18-19Z TIME FRAME...BUT THE STRONGEST
   ACTIVITY IS BECOMING FOCUSED ON THE SOUTHERN FLANK OF THE LINE
   ADVANCING NEAR/NORTH THROUGH EAST OF PEORIA...AIDED BY INFLOW OF
   SOMEWHAT WARMER AND MORE MOIST AIR.

   AS INHIBITION FOR VERY MOIST BOUNDARY LAYER PARCELS /WITH SURFACE
   DEW POINTS IN THE MID 70SF/ CONTINUES TO WEAKEN WITH INSOLATION
   ...FURTHER INTENSIFICATION OF CONVECTION OR SUBSTANTIVE NEW
   DEVELOPMENT APPEARS PROBABLE DURING THE NEXT FEW HOURS ACROSS OR TO
   THE EAST SOUTHEAST OF THE PEORIA/BLOOMINGTON/DECATUR AREA.  DESPITE
   THE PRESENCE OF WEAK TO MODEST MID-LEVEL LAPSE RATES... SEASONABLY
   HIGH MOISTURE CONTENT...WITH PRECIPITABLE WATER WELL IN EXCESS OF
   TWO INCHES...IS SUPPORTING SIZABLE CAPE AND THE POTENTIAL FOR HEAVY
   PRECIPITATION LOADING.  THIS COULD BEGIN TO GRADUALLY CONTRIBUTE TO
   AN INCREASING RISK FOR STRONG DOWNBURSTS...AND PERHAPS AN
   EXPANDING/STRENGTHENING SURFACE COLD POOL.

   WITH DEEP LAYER MEAN FLOW FIELDS TRANSITIONING FROM LIGHT WESTERLY
   TO LIGHT NORTHWESTERLY ACROSS ILLINOIS INTO INDIANA...THE TENDENCY
   MAY BE FOR STRONGEST STORMS TO EVENTUALLY TAKE ON A MORE
   SOUTHEASTERLY PROPAGATION THROUGH THE AFTERNOON HORUS.

   ..KERR/MEAD.. 08/23/2014


   ATTN...WFO...IWX...IND...PAH...LOT...ILX...LSX...

   LAT...LON   39718938 40288943 40708899 41198905 41138891 42298909
               41958822 41378739 40918681 40528624 39408628 38308785
               39718938 

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Page last modified: August 23, 2014
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