551
FXUS63 KIWX 230815
AFDIWX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
415 AM EDT WED JUL 23 2025
KEY MESSAGES
- AFTERNOON HIGHS WILL CLIMB INTO THE 90S THROUGH THURSDAY,
WITH LIMITED OVERNIGHT COOLING. HEAT INDICES OF 95 TO AROUND
100 EXPECTED TODAY, HIGHEST GENERALLY WEST OF US ROUTE 31.
HEAT INDICES OF 100 TO 105 ARE EXPECTED ACROSS THE AREA
THURSDAY AFTERNOON.
- CHANCES FOR SHOWERS AND THUNDERSTORMS BEGIN TO INCREASE
THURSDAY EVENING ALONG AND NORTH OF US-6, SPREADING SOUTH
OVERNIGHT. ADDITIONAL CHANCES FOR SHOWERS AND THUNDERSTORMS
REMAIN FRIDAY INTO SATURDAY, BUT CONFIDENCE ON TIMING AND
LOCATION OF THE BEST CHANCES REMAINS LOW.
- TEMPERATURES WILL REBOUND ONCE AGAIN SUNDAY INTO NEXT WEEK
WITH THE WARMEST DAYS POSSIBLY SUNDAY AND MONDAY.
DISCUSSION
ISSUED AT 346 AM EDT WED JUL 23 2025
INITIAL FOCUS REMAINS ON THE IMPENDING INCREASE IN HEAT AND
HUMIDITY INTO THURSDAY. A RATHER LARGE GRADIENT IN SFC MOISTURE
WAS IN PLACE ACROSS THE FORECAST AREA WITH MID 50 DEWPOINTS NW
TO MID 60S. MID 70 DEWPOINTS ARE NOT THAT FAR AWAY (LEADING EDGE
FROM THE QUAD CITIES TO EVANSVILLE). A SLOWLY INCREASING LLJ
WILL ALLOW THESE TO EDGE IN THROUGH THE DAY TODAY, WITH SOME
QUESTIONS REMAINING HOW FAST THEY SPREAD EAST DURING PEAK
HEATING. THE OVERALL AREA OF THE PREVIOUS HEAT ADVISORY REMAINS
THE MOST LIKELY AREA TO SEE HEAT INDICES EITHER SIDE OF 100
DEGREES. THE ONLY CHANGE MADE TO THIS HEADLINE WAS TO EXTEND IT
IN TIME THROUGH 00Z FRI. THIS WAS DONE FOR 2 REASONS...1)
OVERNIGHT LOWS IN THE LOW TO MID 70S WILL LIMIT COOLING. 2)
ALLOW FOR SIMPLIFIED BLENDING WITH ADDITION OF THE REMAINDER OF
THE AREA INTO A HEAT ADVISORY FOR THURSDAY WHICH WILL BE THE
WARMEST AND POTENTIALLY MOST DANGEROUS DAY FOR HEAT IN THE
COMING DAYS. THAT BEING SAID, THERE IS SOME POTENTIAL MONKEY
WRENCHES THAT COULD LIMIT MUCH HIGHER HEAT INDICES (CLOSER TO
105 OR ABOVE) OR THE DURATION. MODEL SIGNALS HAVE BEEN
INCREASING ON A "COOL FRONT" DROPPING SOUTH ACROSS LOWER MI
THURSDAY AFTERNOON THEN EDGING INTO OUR NORTHERN AREAS THURSDAY
EVENING WITH AT LEAST SCATTERED SHOWERS AND THUNDERSTORMS ALONG
IT AS WELL AS CONVECTIVE DEBRIS THAT IS LIKELY TO BLOW OFF
SOUTHWARD AND ALLOW FOR A TOUCH OF "COOLING" IN THE 21Z THU TO
00Z FRI PERIOD N AND W.
WITH REGARDS TO PRECIPITATION CHANCES...THE OVERALL CONFIDENCE
IS ON THE LOW TO MEDIUM SIDE WITH, AS NOTED, SOME CONVECTION
(LIKELY WEAKENING) THURSDAY NIGHT THAT COULD MOVE THROUGH MUCH
OF THE AREA BEFORE THE FRONT STALLS FRI INTO FRIDAY NIGHT AS THE
BECOMES PARALLEL TO THE UPPER FLOW. MANY MODELS HAVE BACKED OFF
ON OVERALL COVERAGE AND INTENSITY FOR FRI INTO SAT. WITH THE
PROXIMITY OF THE FRONT, A VERY MOIST AIRMASS (PWATS OF 2 TO 2.25
INCHES POOLING IN THE VICINITY OF THE FRONT), REMNANT OUTFLOWS
AND AN OVERALL UNSTABLE ATMOSPHERE, ADDITIONAL DEVELOPMENT
SEEMS LIKELY. HAVE LIMITED POPS STILL TO HIGH LIKELY UNTIL
HOPEFULLY CLEARER SIGNALS APPEAR TO WARRANT CAT POPS. AS THE
FRONT MOVE IN THURSDAY EVENING, MLCAPES EASILY OVER 2000 J/KG
AND POSSIBLY HIGHER, DCAPES AROUND 1000 J/KG AND LIMITED SHEAR
COULD ALLOW FOR SOME POCKETS OF DAMAGING WINDS, ESPECIALLY IF A
SOMEWHAT MORE ORGANIZED LINE CAN FORM. SPC HAS MAINTAINED THE
MARGINAL RISK IN THE NEW DY2 AND WHILE THE SOUTHERN EXTENT IS
LIKELY OVERDONE, OVERALL IT APPEARS VALID. NEW DY3 MAINTAINS
ONLY GENERAL THUNDER AS THE VERY HIGH PWATS, PLENTY OF CLOUD
COVER AND MULTIPLE POSSIBLE ROUNDS OF SHOWERS AND STORMS LEND A
HIGHER FLOOD/FLASH FLOOD POTENTIAL THAN SEVERE. NEW DAY 3
EXCESSIVE RAINFALL OUTLOOK HAS THE SW HALF OF THE AREA IN A
SLIGHT RISK, BUT THIS IS LIKELY TO FLUCTUATE AS THE SETUP
HOPEFULLY BECOMES CLEARER.
NO CHANGES BEYOND SATURDAY AS THE UPPER RIDGE WILL BEING TO
BUILD BACK NORTH BY MONDAY (HEIGHTS PEAKING AT 597 DM). WE COULD
BE LOOKING ONCE AGAIN AT SOME HEAT HEADLINES, BUT ONE CHALLENGE
AT A TIME. PRECIP CHANCES COULD ALSO RETURN TOWARDS THE END OF
THE PERIOD ONCE THE RIDGE BEGINS TO FLATTEN.
AVIATION /06Z TAFS THROUGH 06Z THURSDAY/
ISSUED AT 1224 AM EDT WED JUL 23 2025
THE ATLANTIC SUBTROPICAL RIDGE WILL EXPAND A LITTLE MORE NORTHWEST
INTO THE CONUS AND INTO THE OHIO VALLEY REGION DURING THIS TAF
PERIOD. THIS WILL HELP TO KEEP SKIES MOSTLY CLEAR WITH WINDS
UNDER 10 KTS. VFR CONDITIONS WILL PREVAIL.
IWX WATCHES/WARNINGS/ADVISORIES
IN...HEAT ADVISORY FROM 11 AM TO 8 PM EDT THURSDAY FOR INZ005>009-
017-018-023>027-032>034-116-216.
HEAT ADVISORY FROM 2 PM EDT /1 PM CDT/ THIS AFTERNOON TO 8 PM
EDT /7 PM CDT/ THURSDAY FOR INZ012>015-020-022-103-104-
203-204.
OH...HEAT ADVISORY FROM 11 AM TO 8 PM EDT THURSDAY FOR OHZ001-002-
004-005-015-016-024-025.
MI...HEAT ADVISORY FROM 11 AM TO 8 PM EDT THURSDAY FOR MIZ079>081.
HEAT ADVISORY FROM 2 PM THIS AFTERNOON TO 8 PM EDT THURSDAY
FOR MIZ078-177-277.
MARINE...NONE.
DISCUSSION...FISHER
AVIATION...SKIPPER
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