653  
FXUS63 KIWX 181820  
AFDIWX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE NORTHERN INDIANA  
220 PM EDT FRI JUL 18 2025  
   
KEY MESSAGES
 
 
- A LINE OF STRONG TO SEVERE THUNDERSTORMS IS EXPECTED SATURDAY  
AFTERNOON AND EVENING, WITH DAMAGING WINDS AS THE PRIMARY  
THREAT.  
 
- LOCALLY HEAVY RAINFALL FROM SATURDAY'S STORMS COULD LEAD TO  
ISOLATED INSTANCES OF FLOODING, THOUGH THE PROGRESSIVE NATURE  
OF THE STORMS MAY LIMIT A MORE WIDESPREAD THREAT.  
 
- A SIGNIFICANT A PROLONGED PERIOD OF DANGEROUS HEAT AND  
HUMIDITY IS EXPECTED TO BUILD IN FROM THE MIDDLE TO THE END OF  
NEXT WEEK, WITH HEAT INDICES IN EXCESS OF 100 DEGREES  
ANTICIPATED.  
 

 
   
DISCUSSION
 
 
ISSUED AT 115 PM EDT FRI JUL 18 2025  
 
A QUIET AND PLEASANT DAY IS ON TAP FOR THE CWA TODAY AS HIGH  
PRESSURE PROVIDES US WITH DRY CONDITIONS AND A TOUCH LOWER  
HUMIDITY. THIS WILL BE SHORT-LIVED, HOWEVER, AS SOUTHERLY FLOW  
DEVELOPS TONIGHT, ADVECTING MUCH WARMER/HUMID AIRMASS THAT WILL  
SET THE STAGE FOR AN ACTIVE SATURDAY.  
 
THE PRIMARY CHALLENGE IN THE NEAR TERM IS A MULTI-HAZARD EVENT  
ON SATURDAY, AS THE AREA WILL RESIDE UNDER A VERY UNSTABLE AND  
MOISTURE- RICH ENVIRONMENT OUT AHEAD OF AN APPROACHING COLD  
FRONT. SPC HAS PLACED THE ENTIRE AREA UNDER A SLIGHT RISK (LEVEL  
2 OF 5) FOR SEVERE THUNDERSTORMS. THE MAIN TIME TO WATCH IS  
FROM 12 TO 6PM, BUT STORMS MAY OCCUR AN HOUR OR TWO ON EITHER  
SIDE OF THAT. AMPLE INSTABILITY IS FORECAST, WITH HREF  
SUGGESTING CAPE VALUES AROUND 2,000 J/KG. THIS WILL COMBINE  
WITH MARGINALLY SUFFICIENT WIND SHEAR TO SUPPORT AN ORGANIZED  
LINE OF STRONG TO SEVERE STORMS MOVING THROUGH THE AREA DURING  
THE PM HOURS. THE MAIN THREAT WILL BE DAMAGING WINDS, BUT  
SECONDARY THREATS INCLUDE SMALL HAIL AND A LOW-END CHANCE FOR  
LINE- EMBEDDED TORNADOES.  
 
IN ADDITION TO THE SEVERE THREAT, VERY HIGH MOISTURE CONTENT  
CHARACTERIZED BY PWATS APPROACHING 2IN WILL LEAD TO A THREAT OF  
HEAVY RAINFALL. CONSEQUENTLY, WE HAVE ALSO BEEN PLACED UNDER A  
SLIGHT RISK FOR EXCESSIVE RAINFALL BY WPC. STORMS WILL BE  
CAPABLE OF PRODUCING TORRENTIAL DOWNPOURS THAT COULD LEAD TO  
ISOLATED FLOODING. HOWEVER, THE EXPECTED PROGRESSIVE STORM MODE  
SHOULD HELP LIMIT A MORE WIDESPREAD FLOODING THREAT.  
SIGNIFICANT UNCERTAINTY REMAINS REGARDING THE IMPACT OF ANY  
POTENTIAL MORNING CONVECTION. IF WIDESPREAD SHOWERS AND STORMS  
FORM IN THE MORNING, THEY COULD STABILIZE THE ATMOSPHERE AND  
LIMIT THE AFTERNOON STORM POTENTIAL, A COMMON FORECAST PROBLEM  
IN THE MIDWEST.  
 
COOLER AND DRIER AIR WILL FILTER IN BEHIND THE FRONT FOR  
SUN/MON, PROVIDING A BRIEF BREAK FROM THE ACTIVE WEATHER. DURING  
THIS SUNDAY THROUGH TUESDAY TIMEFRAME, TRENDS SUGGEST THAT ANY  
ORGANIZED COMPLEXES OF STORMS WILL REMAIN JUST TO THE SOUTH AND  
WEST OF OUR REGION, ALTHOUGH THIS WILL NEED TO BE MONITORED -  
ESPECIALLY FOR SUNDAY WHERE CONFIDENCE IN NORTHERN EXTENT OF  
PRECIPITATION IS STILL A BIT UNCERTAIN.  
 
THE FOCUS THEN SHIFTS TO A MAJOR PATTERN CHANGE FOR THE MIDDLE  
AND END OF NEXT WEEK. THERE IS HIGH CONFIDENCE THAT A STRONG  
UPPER-LEVEL RIDGE WILL BUILD ACROSS THE CENTRAL US AND TAKE HOLD  
OVER OUR REGION. THIS WILL BRING A PROLONGED PERIOD OF  
DANGEROUS HEAT AND HUMIDITY, LIKELY FROM WEDNESDAY THROUGH NEXT  
WEEKEND. HIGH TEMPERATURES ARE EXPECTED TO BE NEAR OR ABOVE 90  
DEGREES WITH DEWPOINTS IN THE 70S, LEADING TO POTENTIALLY  
DANGEROUS HEAT INDICES IN EXCESS OF 100 DEGREES. THIS HEAT DOME  
PATTERN WILL ESTABLISH A RING OF FIRE CONVECTIVE REGIME WITH  
STORM COMPLEXES RIDING ALONG THE NORTHERN EDGE OF THE RIDGE,  
BRINGING PERIODIC RAIN CHANCES BACK INTO THE FORECAST FOR THE  
LATTER PART OF THE WEEK.  
 

 
   
AVIATION /18Z TAFS THROUGH 18Z SATURDAY/
 
 
ISSUED AT 129 PM EDT FRI JUL 18 2025  
 
MVFR CIGS OVER THE NEXT SEVERAL HOURS FOR BOTH TAF SITES WITH  
MOIST ISENTROPIC FLOW ALOFT FROM THE SOUTH. DO EXPECT A BIT OF  
IMPROVEMENT IN CIGS INTO VFR CATEGORY TONIGHT INTO THE OVERNIGHT  
HOURS. FOR KFWA DID INCLUDE MENTION IN SOME MIST WITH THE  
INCREASED MOISTURE INFLUX THAT WILL BEGIN SATURDAY MORNING AND  
HAVE VSBYS DOWN TO AROUND 4SM WITH LOWER CERTAINTY TO SEE  
FURTHER DETERIORATION. ALSO THERE IS A POSSIBILITY FOR A BOUT OF  
MORNING SHOWERS/THUNDERSTORMS BUT CONFIDENCE IS NOT HIGH ENOUGH  
AT THIS TIME TO INCLUDE THEM FOR THE MORNING PERIOD. DID INCLUDE  
THE MENTION OF THUNDERSTORMS DEVELOPING OVER THE AREA AFTER 17Z  
SAT FOR BOTH SITES AND WOULD IMAGINE IN THE NEXT UPDATE WILL  
HAVE RAIN/THUNDER IN THE TAFS FOR BOTH SITES BEYOND THIS TAF  
PERIOD.  
 

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

 
 

 
 
DISCUSSION...NORMAN  
AVIATION...ANDERSEN  
 
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