MESOSCALE DISCUSSION 0698
   NWS STORM PREDICTION CENTER NORMAN OK
   0232 PM CDT SAT MAY 07 2011
   
   AREAS AFFECTED...PARTS OF NRN/CNTRL ILLINOIS INTO NORTHWESTERN
   INDIANA
   
   CONCERNING...SEVERE POTENTIAL...WATCH LIKELY 
   
   VALID 071932Z - 072130Z
   
   TRENDS ARE BEING MONITORED FOR THE DEVELOPMENT OF SEVERE STORMS THAT
   PROBABLY WILL REQUIRE A WW LATE THIS AFTERNOON AND EVENING.
   
   A SURFACE FRONTAL ZONE CONTINUES TO BECOME BETTER DEFINED ACROSS
   PARTS OF NORTHERN ILLINOIS AND INDIANA...WITH SOUTHEASTWARD
   DEVELOPMENT OF A LOW CENTER ALONG IT ONGOING ACROSS UPPER PORTIONS
   OF THE MIDDLE MISSISSIPPI VALLEY INTO NORTHWESTERN ILLINOIS.  UPPER
   RIDGING IS BUILDING TO THE WEST...BUT ENHANCED MID-LEVEL FORCING FOR
   ASCENT ASSOCIATED WITH A LOW AMPLITUDE SHORT WAVE IMPULSE STILL
   APPEARS LIKELY TO OVERSPREAD THE FRONT...AND PORTIONS OF THE WARM
   SECTOR TO THE IMMEDIATE SOUTHEAST OF THE LOW...ROUGHLY ALONG/BETWEEN
   THE INTERSTATE 74 AND INTERSTATE 80 CORRIDORS...BETWEEN NOW AND
   22-23Z.
   
   INCREASING LIFT COUPLED WITH ONGOING WEAK TO MODERATE BOUNDARY LAYER
   DESTABILIZATION PROBABLY WILL BE ACCOMPANIED BY VIGOROUS CONVECTIVE
   DEVELOPMENT.  NEAR INTERSECTING LOW-LEVEL THERMAL AND MOISTURE AXES
   EMANATING FROM THE PLAINS /WHERE SURFACE TEMPS ARE APPROACHING 80F
   AND DEW POINTS NEAR 60F/...MIXED LAYER CAPE APPEARS LIKELY TO REACH
   1000 J/KG BY PEAK HEATING.  IN THE PRESENCE OF STRONG SHEAR BENEATH
   THE NORTHERN EDGE OF A 50+ KT 500 MB JET AXIS...ISOLATED SUPERCELL
   DEVELOPMENT APPEARS POSSIBLE ...PERHAPS GROWING UPSCALE INTO A SMALL
   CONVECTIVE CLUSTER CAPABLE OF PRODUCING DAMAGING WIND GUSTS...IN
   ADDITION TO LARGE HAIL.  TORNADIC POTENTIAL IS MORE UNCERTAIN...BUT
   A TORNADO OR TWO MAY NOT BE OUT OF THE QUESTION...PARTICULARLY IN
   RELATIVELY EARLY STAGES OF STORM DEVELOPMENT.
   
   ..KERR.. 05/07/2011
   
   
   ATTN...WFO...IWX...IND...LOT...ILX...DVN...
   
   LAT...LON   41748996 41318732 40748639 39908686 39688760 39658819
               39888956 40458963 41059003 41748996