888  
ACUS11 KWNS 051204  
SWOMCD  
SPC MCD 051204  
INZ000-ILZ000-051430-  
 
MESOSCALE DISCUSSION 1752  
NWS STORM PREDICTION CENTER NORMAN OK  
0604 AM CST SUN NOV 05 2017  
 
AREAS AFFECTED...CENTRAL IL...CENTRAL IN  
 
CONCERNING...SEVERE POTENTIAL...WATCH UNLIKELY  
 
VALID 051204Z - 051430Z  
 
PROBABILITY OF WATCH ISSUANCE...20 PERCENT  
 
SUMMARY...THUNDERSTORM COVERAGE WILL INCREASE OVER THE NEXT HOUR OR  
TWO. SOME SMALL HAIL IS POSSIBLE BUT COVERAGE OF SEVERE  
THUNDERSTORMS WILL BE LIMITED BY MARGINAL INSTABILITY.  
 
DISCUSSION...11Z SURFACE ANALYSIS PLACES A LOW NEAR STL WITH A WARM  
FRONT EXTENDING NORTHEASTWARD THROUGH CENTRAL IL AND INTO NORTHWEST  
OH (ROUGHLY ALONG A STL TO LAF TO FWA TO FDY LINE). WARM ADVECTION  
HAS PERSISTED WITHIN THIS BROAD FRONTAL ZONE THROUGHOUT THE NIGHT,  
HELPING TO MOISTEN THE DRY LAYER OBSERVED BETWEEN 850 AND 700 MB ON  
THE 00Z ILX SOUNDING. THIS WARM ADVECTION IS EXPECTED TO CONTINUE AS  
A SOUTHWESTERLY FLOW ALOFT (ASSOCIATED WITH SHORTWAVE TROUGH  
CURRENTLY NEAR THE NE/IA BORDER) REMAINS OVER THE REGION.  
ADDITIONALLY, THE PROGRESSION OF THIS SHORTWAVE TROUGH AS WELL AS  
THE EASTWARD PROGRESS OF AN UPPER LEVEL JET STREAK WILL CONTRIBUTE  
TO INCREASING LARGE-SCALE FORCING FOR ASCENT. THESE FACTORS ARE  
EXPECTED TO RESULT IN AN INCREASE IN THUNDERSTORM ACTIVITY OVER THE  
NEXT HOUR OR TWO.  
 
GIVEN THE STABLE LOW LEVELS, THIS THUNDERSTORM ACTIVITY IS EXPECTED  
TO BE ELEVATED FOR MUCH OF THE MORNING. THERMODYNAMIC ENVIRONMENT  
CHARACTERIZED BY MOIST LOW LEVELS (I.E. SURFACE DEWPOINTS IN THE MID  
TO UPPER 60S) AND STEEP MID-LEVEL LAPSE RATES WILL SUPPORT MODEST  
INSTABILITY. CURRENT MESOANALYSIS ESTIMATES MUCAPE ACROSS THE REGION  
IS AROUND 500 TO 1000 J/KG. IN ADDITION TO THIS INSTABILITY, A  
STRONGLY SHEARED ENVIRONMENT, LARGELY A RESULT OF STRONG SPEED  
SHEAR, IS IN PLACE. RECENT ILX VAD SAMPLED 0-6 KM BULK SHEAR OVER 50  
KT. THIS TYPE OF ENVIRONMENT SUPPORTS ROTATING THUNDERSTORMS AND  
PERHAPS SOME SMALL HAIL (I.E. LESS THAN 1 INCH IN DIAMETER). OVERALL  
SEVERE POTENTIAL WILL BE MITIGATED BY LIMITED INSTABILITY BUT TRENDS  
ACROSS THE REGION WILL BE MONITORED CLOSELY.  
 
..MOSIER/EDWARDS.. 11/05/2017  
   
..PLEASE SEE WWW.SPC.NOAA.GOV FOR GRAPHIC PRODUCT
 
 
ATTN...WFO...IWX...IND...LOT...ILX...LSX...  
 
LAT...LON 40129010 40608881 40858725 40868597 39868582 39188715  
38678956 39189025 40129010  
 
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