618  
AWUS01 KWNH 190241  
FFGMPD  
MIZ000-INZ000-WIZ000-ILZ000-190845-  
 
MESOSCALE PRECIPITATION DISCUSSION 0957  
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD  
1040 PM EDT MON AUG 18 2025  
 
AREAS AFFECTED...SOUTHERN WI...NORTHERN HALF OF IL...NORTHWEST  
IND...FAR SOUTHWEST LP OF MI...  
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING LIKELY  
 
VALID 190245Z - 190845Z  
 
SUMMARY...INCIDENTS OF FLASH FLOODING LIKELY TO CONTINUE, YET  
OVERALL COVERAGE/TOTALS WILL REDUCE WITH INCREASING FORWARD SPEED.  
BEST CHANCE FOR FLASH FLOODING WILL BE NEW 'REPEATED' CELL TRACKS  
ACROSS S WI/NE IL  
 
DISCUSSION...GOES-E WV, RADAR AND RAP ANALYSIS SHOW SOUTHERN  
STREAM, CONVECTIVELY ENHANCED SHORTWAVE/MCV FEATURE IS PRESSING  
EASTWARD ACROSS CHICAGO INTO SOUTHERN LAKE MICHIGAN AT THIS TIME,  
CONTINUING TO DRIVE STRONGEST DOWNSTREAM LOW LEVEL CONVERGENCE  
ALONG THE QUASI-BOWING FEATURE FROM NORTHWEST IND SOUTHWARD ACROSS  
THE KANKAKEE VALLEY. STORMS REMAIN IN UNSTABLE ENVIRONMENT WITH  
AMPLE DEEP LAYER MOISTURE (TDS IN THE MID 70S AND TOTAL MOISTURE  
OVER 2"), BUT THE STATIONARY FRONT REMAINS ANCHORED ACROSS  
SOUTHWEST LP OF MI INTO NORTH-CENTRAL IND BEFORE TDS AND UNSTABLE  
AIR RAPIDLY SROP OFF, SO THERE IS A NARROW AREA OF ENHANCED  
RAINFALL RATES UP TO 2", BUT CELLS SHOULD QUICKLY DIMINISH INTO  
THE MORE STABLE AIR. ADDITIONALLY, AREA ACROSS LP OF MI AND  
NORTHEAST IND HAS BEEN MUCH DRIER AND FFGS REFLECT THAT, FURTHER  
REDUCING THE RISK TO ALL BUT THE MOST IDEAL TRAINING ACROSS  
URBAN/LOW INFILTRATION GROUND CONDITIONS.  
 
HOWEVER, THE UPSTREAM FLANKING LINE ACROSS INTO CENTRAL IL, DOES  
REMAIN VERY UNSTABLE WITH MUCAPES OF 2000-3000 J/KG AND SOLID  
MOISTURE FLUX CONVERGENCE ALONG THE CONFLUENT LOW LEVEL FLOW  
REGIME. DEEP LAYER STEERING MAY ALLOW FOR SOME SOUTHWEST TO  
NORTHEAST REPEATING, THOUGH HEIGHT-FALLS FROM THE PASSING  
SHORTWAVE/MCV SHOULD ALLOW FOR SOUTHEAST PROPAGATION TO LIMIT  
OVERALL TOTALS TO 2-3", LOWER FFG VALUES OF LESS THAN 2"/HR AND  
1.5-2.5"/3HRS IN ALL BUT THE FURTHER SOUTHWEST PORTIONS OF CENTRAL  
IL REMAIN AT GOOD RISK OF LOCALLY BEING EXCEEDED THROUGH THE NEXT  
FEW HOURS.  
 
FURTHER NORTH...S WI/N IL...  
GOES-E WV DEPICTS CORE OF LARGER/SYNOPTIC TO MESOSCALE SHORTWAVE  
FEATURE ACROSS CENTRAL TO S WI, IS EXITING AND DOWNWARD MIXING IS  
STARTING TO HELP ADVANCE THE STATIONARY FRONT ACROSS SW WI THROUGH  
DEPTH, SHARPENING CONVERGENCE ALONG AND SOUTH OF THE BOUNDARY.  
WHILE PARTIALLY MIXED, THERE REMAINS AMPLE REMAINING UNSTABLE AIR  
OF 1500-2000 J/KG AND AMPLE DEEP LAYER MOISTURE TO SUPPORT AN  
ADDITIONAL ROUND OF STRONGER THUNDERSTORMS. THESE UPSTREAM  
THUNDERSTORMS WILL BE NARROWER IN NATURE BUT SHOULD HAVE THE  
OPPORTUNITY TO TRACK ACROSS AREAS ALREADY AFFECTED BY HEAVY  
RAINFALL WITH RATES OF 1.75-2"/HR; LOCALIZED ADDITIONAL 1-3"  
TOTALS WOULD REAGGRAVATE ANY FLOODING CONDITIONS ACROSS S WI AND  
FEW NORTHERN ROWS OF N IL. AS SUCH, LOCALIZED INCIDENTS OF FLASH  
FLOODING ARE LIKELY TO PERSIST THROUGH THE OVERNIGHT PERIOD.  
 
GALLINA  
   
..PLEASE SEE WWW.WPC.NCEP.NOAA.GOV FOR GRAPHIC PRODUCT  
 
ATTN...WFO...DVN...GRR...ILX...IND...IWX...LOT...MKX...  
 
ATTN...RFC...MSR...TIR...NWC...  
 
LAT...LON 43398673 43118619 42518584 41708587 40518639  
39988741 39908888 40019006 40469037 40869000  
41278958 41708930 42168939 42489001 42988980  
43348839  
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