505  
FXUS63 KIWX 090548  
AFDIWX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE NORTHERN INDIANA  
148 AM EDT WED JUL 9 2025  
   
KEY MESSAGES
 
 
- SEASONABLY WARM & HUMID CONDITIONS WILL PERSIST, WITH DAILY  
MAXIMUM HEAT INDEX VALUES IN THE UPPER 80S TO AROUND 90  
DEGREES.  
 
- AN ACTIVE WEATHER PATTERN WILL RETURN ON WEDNESDAY, RESULTING  
IN FREQUENT FOR SHOWERS AND THUNDERSTORMS OVER THE NEXT  
SEVERAL DAYS.  
 
- SEVERE WEATHER CHANCES ARE EXPECTED TO REMAIN LOW. HOWEVER,  
LOCALLY HEAVY RAINFALL MAY BECOME A CONCERN THIS WEEKEND.  
 

 
   
DISCUSSION
 
 
ISSUED AT 130 PM EDT TUE JUL 8 2025  
 
AN ACTIVE WEATHER PATTERN WILL RETURN TO THE AREA OVER THE NEXT  
SEVERAL DAYS WITH THE PASSAGE OF NUMEROUS MID AND UPPER-LEVEL  
DISTURBANCES. A WELL-DEFINED SHORT WAVE TROUGH AXIS WILL  
TRAVERSE THE AREA THIS AFTERNOON AND EVENING, WITH NUMEROUS  
SHOWERS AND STORMS LIKELY DEVELOPING UPSTREAM ACROSS IL. MOST  
HIGH-RES MODELS SUGGEST THIS ACTIVITY SHOULD DISSIPATE OR AT  
LEAST WEAKEN SIGNIFICANTLY PRIOR TO REACHING OUR WESTERN ZONES  
AFTER 00Z W/ THE LOSS OF DIURNAL INSTABILITY, BUT NONETHELESS A  
FEW LIGHT SHOWERS WILL REMAIN POSSIBLE THROUGH THE NIGHT ACROSS  
THE ENTIRE CWA. ISOLATED TO WIDELY SCATTERED STORMS WILL BE A  
POSSIBILITY AGAIN DURING THE LATE AFTERNOON AND EARLY EVENING  
HOURS ON WEDNESDAY WITH A SUBTLE RIPPLE IN THE FLOW / WEAK VORT  
MAX ON THE BACK SIDE OF THE AFOREMENTIONED TROUGH. AFTER A BRIEF  
LULL DURING THE DAY ON THURSDAY, MODELS SUGGEST A RATHER COMPLEX  
PATTERN EVOLUTION W/ TWO HIGHLY ENERGETIC SOUTHERN AND NORTHERN  
STREAM DISTURBANCES INTERACTING OVER THE CENTRAL PLAINS. WHILE  
THE EXACT EVOLUTION OF THIS PATTERN REMAINS A BIT MUDDY AT THIS  
TIME, PRECIPITATION CHANCES SHOULD INCREASE MARKEDLY ESPECIALLY  
FROM FRIDAY NIGHT THROUGH SATURDAY. FORECAST VERTICAL PROFILES  
APPEAR EXTREMELY MOIST WITH VERY TALL/SKINNY CAPE PROFILES,  
SUPPORTING A THREAT FOR LOCALLY HEAVY RAINFALL WHICH IS  
HIGHLIGHTED IN THE LATEST WPC DAYS 4/5 EXCESSIVE RAINFALL  
OUTLOOKS. AT THIS TIME, THIS DOES NOT APPEAR TO BE A WIDESPREAD  
HEAVY RAIN EVENT THOUGH W/ THE LATEST NBM SPECTRUM SUGGESTING  
ONLY AROUND A 20% CHANCE OF EXCEEDING 0.5 INCH QPF ACROSS MUCH  
OF THE AREA DESPITE A FEW DETERMINISTIC RUNS HINTING AT MUCH  
MORE ROBUST TOTALS. OTHERWISE, SEASONABLY HOT AND HUMID  
CONDITIONS WILL PERSIST W/ THE MORE SUBSTANTIAL HUMIDITY  
ARRIVING IN TIME FOR THE WEEKEND WHICH MAY HELP PUSH HEAT  
INDICES INTO THE LOWER 90S.  
 

 
   
AVIATION /06Z TAFS THROUGH 06Z THURSDAY/
 
 
ISSUED AT 145 AM EDT WED JUL 9 2025  
 
A CONVECTIVELY ENHANCED SHORT WAVE WILL CONTINUE TO TRACK ACROSS  
NORTHERN INDIANA THIS MORNING WITH SOME SCATTERED SHOWERS AND  
ISOLATED THUNDERSTORMS. INSTABILITY IS A LIMITING FACTOR  
HOWEVER, WITH CIN FOR NEAR SFC BASED PARCELS PERSISTING.  
CONFIDENCE AT THIS TIME IS TOO LOW FOR INCLUSION OF SHOWERS AT  
TERMINALS OVERNIGHT, BUT TRENDS WILL CONTINUE TO BE MONITORED  
THROUGH THE DAYBREAK. THE BEST CHANCE MAY BE AT KSBN WHERE  
REMNANT MCV FEATURE ACROSS NE ILLINOIS COULD SPEAK SOME EARLY  
MORNING SHOWERS/ISOLATED STORMS. BROAD UPSTREAM UPPER TROUGH  
WILL TAKE A BAGGY SFC TROUGH/COOL FRONT INTO NORTHERN INDIANA  
TODAY WITH A DIURNAL UPTICK IN SHOWERS AND EMBEDDED STORMS  
EXPECTED. THIS POTENTIAL APPEARS TO AFFECT BOTH TERMINALS AND  
WILL CONTINUE IDEA FROM PREVIOUS FORECAST IN PROB30 MENTION  
THROUGH MID/LATE AFTERNOON AT KSBN, AND MID AFTERNOON THROUGH  
EARLY EVENING AT KFWA BASED ON FRONTAL TIMING. DRIER LOW LEVEL  
AIR WILL EVENTUALLY SEEP INTO NORTHERN INDIANA TONIGHT BEHIND  
THIS FRONT. THIS SETUP COULD YIELD SOME PATCHY SHALLOW FOG  
DEVELOPMENT ACROSS NE INDIANA EARLY THURSDAY MORNING BUT THIS  
WILL BE ADDRESSED IN NEXT TAF ISSUANCE.  
 

 
   
IWX WATCHES/WARNINGS/ADVISORIES
 
 
IN...NONE.  
OH...NONE.  
MI...NONE.  
MARINE...NONE.  
 

 
 

 
 
DISCUSSION...HAMMER  
AVIATION...MARSILI  
 
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