558
FXUS63 KIWX 032257
AFDIWX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
657 PM EDT THU SEP 3 2026
KEY MESSAGES
- HEAT AND HUMIDITY CONTINUE THROUGH WITH PEAK HEAT INDICES
AROUND 100 DEGREES.
- 20-30% CHANCE OF THUNDERSTORMS TONIGHT. ANOTHER CHANCE FOR
STORMS OCCURS EARLY FRIDAY AND POTENTIALLY AGAIN FRIDAY
AFTERNOON/EVENING.
- THUNDERSTORMS ARE IN THE FORECAST AGAIN FOR SATURDAY.
- A DRY PATTERN TAKES OVER SUNDAY THROUGH TUESDAY.
DISCUSSION
ISSUED AT 204 PM EDT THU SEP 3 2026
WE CONTINUE TO HAVE THIS STRONG RIDGE ACROSS THE SOUTHEAST INTO THE
END OF THE WORK WEEK WITH HIGH HEAT (18C+ 850 MB TEMPS THAT ARE
CONDUCIVE TO 90F SFC TEMPS WITH MIXING AND 70 DEGREE DEW POINTS)
THAT LOOK TO CONTINUE UNTIL WE CAN GET SOME WEATHER IN HERE OR A
WEAKNESS FORMS IN THE UPPER RIDGING.
WE DO HAVE THE RISK OF SEVERE WEATHER TODAY (SLIGHT RISK FROM SPC)
THAT WITH THE HIGH HEAT AND INSTABILITY COULD PRODUCE SOME SEVERE
WEATHER, PRIMARILY WEST OF IN-15 AND NORTH OF US-6 WHERE THE BETTER
SHEAR SEEMS TO RESIDE. THE BETTER FLOW IS NORTH AND WEST OF THE AREA
AND THE NAM SEEMS TO WANT TO SPARK SOME STRONGER CONVECTION IN THE
18Z WINDOW ACROSS WI TODAY AND MOVE IT SOUTHEAST INTO THE EVENING.
IF WE CAN GET SOME GOOD CONVERGENCE TO GET SOME ASCENT WITHIN THE
BETTER JET KINEMATICS TO THE NORTH, THAT WOULD SEEM TO BE ENOUGH TO
ERODE THE CAP AND SPARK SOME THUNDERSTORMS ACROSS THE AREA. AN
OUTFLOW BOUNDARY PUSHES INTO THE AREA AND PUSHES SOUTHEASTWARD AND
LIKELY BECOMES A FOCUS FOR STORMS THIS AFTERNOON. THE HRRR AND THE
RAP DON'T SEEM TOO ENTHUSIASTIC ABOUT IT THOUGH AND SO WILL CONTINUE
WITH THE LOW 20 TO 30 PERCENT CHANCE POPS THAT HAVE A THREAT FOR
WIND, HAIL.
THIS PUTS THE AREA IN A BIT OF A BIND FOR WHAT TO DO FOR FRIDAY AS
FAR AS HEAT HEADLINES GO. SINCE THIS DEPENDS ON IF OVERNIGHT
CONVECTION CAN HAPPEN OR NOT, DO NOT HAVE A LOT OF CONFIDENCE.
INDIVIDUAL MODEL GUIDANCE SEEMS TO PLACE THE BEST CHANCE (35 TO 40%)
FOR HEAT HEADLINES ACROSS PULASKI AND FULTON, WHITE TO MIAMI, AND
PERHAPS STARKE COUNTY AS WELL, IN INDIANA FOR FRIDAY, BUT THERE IS
SOME CHANCE FOR AREAS ALONG AND SOUTH OF US-30. THIS WOULD BE MOSTLY
REMOVED FROM WHERE THUNDERSTORMS ARE POSSIBLE ON FRIDAY AT LEAST
WHERE MODEL QPF IS BEING RESOLVED. THE ISSUE IS THAT MODELS ARE ALL
OVER THE PLACE WITH THE LOCATION OF THE LOW LEVEL JET FOR FRIDAY,
WHICH ALSO PROVIDES LOWER CONFIDENCE FOR HEAT HEADLINES. AFTER
COLLABORATION WITH NEIGHBORING COUNTIES HAVE SETTLED WITH THE FIRST
FIVE COUNTIES MENTIONED ABOVE IN A HEAT ADVISORY FOR FRIDAY WHERE
THE HIGHEST CONFIDENCE RESIDES WITH RESPECT TO STORM POTENTIAL AND
HEAT INDEX FORECAST. IT IS POSSIBLE THAT SOME TWEAKING TAKES
PLACE IN FOLLOWING FORECAST SHIFTS ONCE STORM POTENTIAL AND
CLOUD DEBRIS BECOMES BETTER REALIZED.
THE NAM AND GFS HAVE MODEL CONFLUENCE AROUND A LOW LEVEL JET (OF
DIFFERENT MAGNITUDES) DIVING SOUTHEAST THROUGH THE AREA, LIKELY IN
CONJUNCTION WITH A CONVECTIVE WAVE FRIDAY EVENING/NIGHT. THE ECMWF
DOES RESOLVE SOME QPF ASSOCIATED WITH THE LOW LEVEL WARM ADVECTION,
BUT THOSE ARE LOWER IN MAGNITUDE THAN THE GFS AND NAM PROVIDING
LOWER CONFIDENCE AGAIN.
THERE DOES APPEAR TO BE BETTER MODEL AGREEMENT AROUND A BACKDOOR
COLD FRONT THAT WOULD BRING HEAT RELIEF AND PUSH THUNDERSTORM
CHANCES FARTHER SOUTHWEST AS THE UPPER RIDGING BUCKLES AND A MID
LEVEL TROUGH WORKS INTO THE NORTHEAST US SATURDAY NIGHT/SUNDAY TIME
FRAME. THIS WOULD KEEP THE AREA DRY FROM SUNDAY THROUGH TUESDAY.
WE'RE BACK INTO THE HIGH HEAT AND HUMIDITY BY WEDNESDAY AS ANOTHER
RIDGE BUILDS INTO THE WESTERN CONUS AND PUSHES EASTWARD TOWARD OUR
AREA. A WAVE APPROACHING FOR TUESDAY EVENING/NIGHT MAY BRING OUR
NEXT CHANCE FOR SHOWERS AND STORMS. ANOTHER TROUGH WINDS THROUGH
THURSDAY PROVIDING ANOTHER RAIN AND TAKING AWAY THE HEAT. IT IS
POSSIBLE THAT THE HEAT SORT OF JOCKEYS AROUND LASTS LONGER THAN JUST
A DAY, BUT THIS ONE DAY HEAT CHANCE LOOKS MOST LIKELY AT THIS
POINT.
AVIATION /00Z TAFS THROUGH 00Z SATURDAY/
ISSUED AT 657 PM EDT THU SEP 3 2026
DRY/VFR WITH LIGHT WINDS FOR MOST OF TONIGHT AS COMPOSITE
OUTFLOW BOUNDARY AND ASSOCIATED CONVECTION HAS CLEARED OFF TO
THE SOUTH. THERE ARE LOW CHANCES (20-30%) FOR SCATTERED
SHOWERS/STORMS LATER TONIGHT INTO FRIDAY AS ADDITIONAL
CONVECTION COULD TOP THE UPPER RIDGE IN THE VICINITY OF THE
PRIMARY THETA-E RIDGE, THOUGH CONFIDENCE IN TIMING IS TOO LOW
FOR MENTION IN THE TAF AT THIS TIME.
IWX WATCHES/WARNINGS/ADVISORIES
IN...HEAT ADVISORY UNTIL 8 PM EDT /7 PM CDT/ THIS EVENING FOR
INZ005>009-012-014-017-018-024>027-032>034-103-104-116-
203-204-216.
HEAT ADVISORY UNTIL 8 PM EDT FRIDAY FOR INZ013-015-020-022-023.
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...ROLLER
AVIATION...STEINWEDEL
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