411
FXUS63 KIWX 241735
AFDIWX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
135 PM EDT THU JUL 24 2025
KEY MESSAGES
- VERY HOT AND HUMID AIRMASS IMPACTS THE AREA TODAY WITH PEAK
AFTERNOON HEAT INDICES OF 100 TO 105 (HIGH CONFIDENCE) WITH A
POTENTIAL OF SOME AREAS REACHING 105 TO 110 (LOWER
CONFIDENCE).
- CHANCES FOR SHOWERS AND THUNDERSTORMS BEGIN TO INCREASE LATE
THIS AFTERNOON INTO EVENING ALONG AND NORTH OF US-6, SPREADING
SOUTH OVERNIGHT. AN ISOLATED DAMAGING WIND THREAT AND LOCALLY
HEAVY RAINFALL WOULD BE THE POTENTIAL MAIN THREATS.
- WHILE ADDITIONAL CHANCES FOR SHOWERS AND THUNDERSTORMS EXIST
FRIDAY AND SATURDAY, CONFIDENCE REMAINS LOW REGARDING
COVERAGE/TIMING. HEAVY RAIN WOULD BE THE MAIN THREAT WITH ANY
STORMS.
- HEAT INDICES MAY APPROACH 100 DEGREES ONCE AGAIN SUNDAY AND
MONDAY, BUT WILL DEPEND ON CLOUD COVER AND ANY SHOWERS OR
STORMS.
DISCUSSION
ISSUED AT 304 AM EDT THU JUL 24 2025
WELL ADVERTISED HOT AND HUMID DAY IN STORE WITH TEMPERATURES IN THE
LOW 90S AND DEWPOINTS IN THE 70S BRINGING WIDESPREAD HEAT INDICES OF
100 TO 105, ALONG WITH SOME POCKETS OF SOMEWHAT HIGHER VALUES
POSSIBLE. CURRENT HEADLINES HAVE EVERYTHING IN HAND AT THIS POINT SO
NO CHANGES IN TYPE OR DURATION.
NEXT AREA OF CONCERN WILL REVOLVE AROUND CHANCES FOR SHOWERS AND
THUNDERSTORMS LATER THIS AFTERNOON INTO TONIGHT. LINE OF SHOWERS AND
STORMS EXTENDED FROM WEST CENTRAL WI INTO CENTRAL IA WILL CONTINUE
EAST AND LIKELY WEAKEN TOWARDS MORNING. REMNANT OUTFLOWS ARE LIKELY
TO PUSH EAST THROUGH THE DAY ACROSS IL AND EVENTUALLY INTO NW
PORTIONS OF THE AREA, NEAR THE SAME TIME A SYNOPTIC BOUNDARY SHOULD
BE DRIFTING SE INTO THE AREA. CHALLENGE REMAINS AS TO POTENTIAL
DEVELOPMENT OF ISOLATED SHOWERS/STORMS ACROSS THE AREA DURING PEAK
HEATING AND TIMING OF DEVELOPMENT IN THE NW WITH ABOVE NOTED
FEATURES. LACK OF NOTED LIFTING MECHANISMS FOR MOST OF THE AREA
UNDER THE INFLUENCE OF THE RIDGE MAY VERY WELL PREVENT ANY
DEVELOPMENT AWAY FROM NW AREAS. WILL LEAVE THE SLGT CHC POPS IN
PLACE FOR THE TIME BEING GIVEN THE NON-ZERO THREAT FOR 1 OR 2 STORMS
TO POP. WITH REGARDS TO TIMING IN THE NW CAMS FOR THE PAST SEVERAL
DAYS HAVE STRUGGLED TO HONE IN ON A FAVORED TIME FRAME WITH SOME AS
EARLY AS 21Z TO AS LATE AS 2Z. ONCE INITIATION OCCURS, THE AREA
SHOULD ADVANCE SE AND EVENTUALLY WEAKEN OVERNIGHT. 1500-2000 J/KG
SBCAPE WILL BE IN PLACE ALONG WITH HIGH PWATS AND LIMITED SHEAR TO
BRING A THREAT FOR STRONGER CELLS TO PRODUCE WIND GUSTS, MAINLY
DURING THE LATE AFTERNOON AND EARLY EVENING HOURS. ANY STORMS SHOULD
DRIFT SLOWLY SOUTHEAST BUT OVERALL SPEED AND CHANCE FOR SOME
REDEVELOPMENT UPSTREAM COULD LEAD TO SOME MINOR FLOOD CONCERNS.
FORECAST EVOLUTION EVEN MORE UNCERTAIN WITH REGARDS TO CHANCES FOR
ADDITIONAL DEVELOPMENT FRIDAY INTO SAT AS EFFECTIVE BOUNDARY REMAINS
IN THE AREA AND A SERIES OF WEAK DISTURBANCES AND REMNANT OUTFLOWS
ALLOWS FOR 1 OR MORE POTENTIAL ROUNDS OF SHOWERS AND STORMS.
CONSENSUS OF SURROUNDING OFFICES WAS TO LIMIT HIGHEST POPS TO FRIDAY
AFTERNOON FOR THE TIME BEING. PWATS WELL OVER 2" AND DEEP WARM CLOUD
LAYER POINTS TOWARD A HEAVY RAIN THREAT WITH ANY STORMS WITH THE
OVERALL FLOW SUGGESTING SLOW MOVEMENT AND SOME BACKBUILDING
POTENTIAL. EXCESSIVE RAINFALL OUTLOOK HAS CHANGED LITTLE WITH SLIGHT
RISK SW HALF AND MARGINAL ELSEWHERE. CHANGES COULD VERY WELL
HAPPENING OVER THE NEXT 24 TO 36 HOURS AS MESOSCALE FEATURES BECOME
CLEARER. WITH THE CLOUDS AND PRECIP AROUND, CONCERNS FOR HEAT
HEADLINES APPEAR LOW, BUT IF CONVECTION DOES NOT DEVELOP OR REMAINS
WIDELY SCATTERED SOME HEADLINES COULD BE NEEDED. ANOTHER COMPLEX OF
STORMS MAY DEVELOP UPSTREAM AND MOVE IN LATE FRI NIGHT INTO SAT.
HAVE LEFT BLEND OF HIGH CHC TO LIKELY POPS BUT SKEPTICISM CONTINUES
WITH THE SAME INHERENT ISSUES ALREADY OUTLINED.
RIDGING BUILDS IN AGAIN FOR SUN-MON WITH YET ANOTHER POTENTIAL RUN
AT HEAT INDICES NEAR 100 DEGREES. RIDGE AXIS WILL BE JUST TO THE WEST
WHICH COULD ALLOW FOR SOME ISOLATED SHOWER/STORM DEVELOPMENT THAT
HAMPERS THE THREAT FOR ADVISORY LEVEL TEMPS. BEYOND MONDAY, FORECAST
IS RIDDLED WITH SLGT CHC TO CHC POPS MAINLY DURING THE AFTERNOON AND
EVENING AS A OVERALL NW FLOW SETUPS ALOFT AND SERIES OF WEAK WAVES
BRING SOME CHANCES FOR SHOWERS AND STORMS.
AVIATION /18Z TAFS THROUGH 18Z FRIDAY/
ISSUED AT 134 PM EDT THU JUL 24 2025
A BOUNDARY APPROACHES AT 00Z THIS EVENING AND MAY BE THE FOCUS FOR A
FEW SCATTERED SHOWERS AND THUNDERSTORMS. DUE TO INSTABILITY, A FEW
SEVERE THUNDERSTORMS WITH DAMAGING WIND GUSTS COULD OCCUR, BUT
FLOODING DUE TO HEAVY RAIN APPEARS TO BE THE MAIN THREAT. WILL
HANDLE THIS WITH PROB30 GROUP STILL WITH THIS ISSUANCE AS THERE
STILL REMAINS QUITE A BIT OF UNCERTAINTY AROUND WHEN STORMS WILL
START. THE HRRR IS ONE OF THE FEW MODELS THAT KEEPS STORMS
GOING INTO THE OVERNIGHT PERIOD AND THERE IS STILL A POSSIBILITY
THAT THUNDERSTORMS REMAIN AROUND SBN. IT WOULD LIKELY TAKE
UNTIL LATE NIGHT OR EARLY MORNING FRIDAY TO GET THE LINE PUSHED
SOUTHWARD TOWARDS FWA. WILL USE A PROB30 GROUP FOR THEM TOO. AT
LEAST MVFR CONDITIONS ARE POSSIBLE, BUT IFR CONDITIONS COULD
STILL OCCUR IN SOME OF THE HEAVIER RAIN. WINDS ARE EXPECTED TO
REMAIN MOSTLY OUT OF THE SW, HOWEVER, BRIEF PERIODS OF NW
DIRECTIONS COULD OCCUR BEHIND THE VARIOUS BOUNDARIES THAT MOVE
THROUGH. WIND GUSTS BETWEEN 20 AND 25 KTS WILL BE POSSIBLE THIS
AFTERNOON BEFORE SUNSET AS MIXING OCCURS.
IWX WATCHES/WARNINGS/ADVISORIES
IN...HEAT ADVISORY UNTIL 8 PM EDT /7 PM CDT/ THIS EVENING FOR
INZ005>009-012>015-017-018-020-022>027-032>034-103-104-
116-203-204-216.
OH...HEAT ADVISORY UNTIL 8 PM EDT THIS EVENING FOR OHZ001-002-004-
005-015-016-024-025.
MI...HEAT ADVISORY UNTIL 8 PM EDT THIS EVENING FOR MIZ078>081-177-
277.
MARINE...NONE.
DISCUSSION...HAMMER
AVIATION...ROLLER
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