241
FXUS63 KIWX 131743
AFDIWX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
143 PM EDT MON JUL 13 2026
KEY MESSAGES
- HIGH HEAT IS FORECAST FOR TUESDAY AND WEDNESDAY WITH HEAT
INDICES AROUND OR ABOVE 100F. A HEAT ADVISORY HAS BEEN ISSUED
FOR TUESDAY. IT IS POSSIBLE THAT THE HIGH HEAT CONTINUES INTO
THE LATER PART OF THE WORK WEEK AS WELL.
- THE POTENTIAL FOR SHOWERS AND THUNDERSTORMS (20-40%) ENTERS THE
FORECAST LATE THIS WEEK INTO THIS WEEKEND.
DISCUSSION
ISSUED AT 137 PM EDT MON JUL 13 2026
THE SHORT TERM WEATHER IS DOMINATED BY A RIDGE OF HIGH PRESSURE OVER
THE AREA. OVER THE COURSE OF THIS WEEK, A TROUGH BUILDS INTO THE
NORTHEASTERN US AND THIS BUCKLES THE RIDGE STRENGTH POTENTIALLY
BRINGING COOLER WEATHER AND PROBABLY BRINGS MORE UNSETTLED WEATHER
BY THE END OF THE WEEK.
THE FIRST ISSUE IN THE SHORT TERM IS THE HEAT POTENTIAL TUESDAY AND
WEDNESDAY. THE 850 MB TEMPERATURES CONDUCIVE TO 90F HIGH TEMPS WITH
MAXIMUM MIXING ACTUALLY BUILD INTO THE AREA TODAY AS 850 MB SURPASS
18C. HOWEVER, WITH EAST WINDS, DRIER HUMIDITY REMAINS ACROSS THE
AREA. THERE IS ACTUALLY SOME POSSIBILITY THAT 70F DEGREE DEW POINTS
BEGIN POKING INTO NORTHWESTERN PARTS OF THE AREA THIS EVENING AS
SFC TEMPERATURES BEGIN TO DROP WITH THE SUNSET. FOR TUESDAY,
850 MB TEMPERATURES SURPASS 23C WHICH OFTEN LEADS TO 95F WITH
MAXIMUM MIXING AND 70F DEW POINTS PUSH FARTHER INTO THE AREA
DURING THE DAY. THE GREATEST CONFIDENCE IS IN AREAS NORTH OF
US-24 SEEING THIS COMBINATION OF 90+F HIGH TEMPS AND 70F DEW
POINTS THAT LEADS TO 100- 105F HEAT INDICES. AS SUCH, HAVE
HOISTED HEAT ADVISORY HEADLINES FOR THAT AREA. THIS GIVES THE
NEXT SHIFT ONE LAST LOOK TO FINE TUNE HEADLINES BEFORE ONSET.
FOR WEDNESDAY, IT IS INTERESTING TO SEE THAT THE GFS IS COOLER
THAN THE ECMWF AS THE GFS KEEPS 850 MB TEMPS COOLER THAN THE
ECMWF'S 23+C. MEANWHILE, IT WOULD APPEAR THAT THE ECMWF MIXES
DEW POINTS BACK INTO THE 60S IN SOME AREAS WEDNESDAY. PERHAPS
THE EVAPOTRANSPIRATION FACTOR COULD BE LOWER SINCE MANY OF
THOSE AREAS WITH CORN HAVE NOT RECEIVED RAIN IN A WHILE. GIVEN
THIS UNCERTAINTY HAVE STOOD DOWN FROM HEAT HEADLINES FOR
WEDNESDAY. THE OTHER ISSUE IS THE AMOUNT OF DRYING THAT TAKES
PLACE ON THURSDAY. CONFIDENCE IS STILL RELATIVELY LOW ON ITS
PLACEMENT AND THIS COULD AFFECT BOTH TEMP AND DEW POINTS IN THE
AREA. THE ECMWF INDICATES THERE COULD ALSO BE MIXING ISSUES EVEN
IF THE FRONT DOESN'T MAKE IT INTO THE AREA. WHEN THE OVERNIGHT
HEAT INDICES STRUGGLE TO DROP BELOW 72F OR SO, LITTLE RELIEF IS
FELT OVERNIGHT, AND WHEN DAYTIME HEAT INDICES ARE AROUND 100F OR
SO DURING THE DAYTIME, THREE CONSECUTIVE DAYS OF SUCH
CONDITIONS CAN PUT A STRAIN ON SOCIETY. THE LOWER CONFIDENCE OF
A THIRD DAY OF HEAT SURPASSING HEAT ADVISORY THRESHOLDS AS WELL
AS OVERNIGHT HEAT INDICES BEING MORE LIKE 70 OR 71F DISQUALIFIES
THIS EVENT FROM THAT THE EXCESSIVE HEAT WARNING CRITERIA WHEN
LOOKING AT IT THIS FAR OUT. IT IS INTERESTING TO SEE THAT 70F
DOES STILL PUSH ITS WAY INTO THE AREA AT LEAST THROUGH SUNDAY
AND IS POSSIBLE AT LEAST INTO NEXT WEEK DEPENDING ON WHAT MODEL
YOU LOOK AT. AT THE SAME TIME, BUCKLING THE RIDGE WOULD PROVIDE
LESS CONFIDENCE IN SEEING THE HIGH HEAT CONTINUE.
AFTER A LONG PERIOD OF DRY WEATHER, THE NBM HAS CHANCES FOR RAIN
SHOWING UP FRIDAY AFTERNOON IN WHAT APPEARS TO BE A POP CONVECTION
SCENARIO. AS AN MCS MOVES FROM THE UPPER GREAT LAKES TOWARDS THE MID
ATLANTIC/NORTHEAST FRIDAY NIGHT, THERE COULD BE SOME AFTERNOON
CONVECTION SATURDAY AFTERNOON. THE GFS BRINGS THE COLD FRONT THROUGH
THE AREA SATURDAY NIGHT, BUT THE ECMWF KEEPS THE AREA IN THE BETTER
HEATING INTO NEXT WEEK KEEPING RAIN CHANCES ACROSS THE AREA.
AVIATION /18Z TAFS THROUGH 18Z TUESDAY/
ISSUED AT 132 PM EDT MON JUL 13 2026
VFR CONDITIONS ARE EXPECTED AT THE TERMINAL. WITH CLEAR SKIES
AND LIGHT (OR VARIABLE) WINDS, MVFR VISIBILITIES ARE POSSIBLE
LATE TONIGHT/EARLY TUE AM, BUT CONFIDENCE IN HUMIDITY LEVELS WAS
NOT HIGH ENOUGH TO INCLUDE A MENTION IN THE TAF AT THIS TIME.
MUCH OF THE GUIDANCE HAD 6SM OR GREATER, WITH THE EXCEPTION OF A
COUPLE DROPPING TO 4-5SM.
IWX WATCHES/WARNINGS/ADVISORIES
IN...AIR QUALITY ALERT FROM MIDNIGHT EDT /11 PM CDT/ TONIGHT TO
MIDNIGHT EDT /11 PM CDT/ TUESDAY NIGHT FOR INZ005-012>015-
022-023-104-116-204-216.
HEAT ADVISORY FROM NOON EDT /11 AM CDT/ TO 8 PM EDT /7 PM CDT/
TUESDAY FOR INZ005>009-012>015-017-018-020-022>024-103-
104-116-203-204-216.
AIR QUALITY ALERT UNTIL MIDNIGHT CDT TUESDAY NIGHT FOR INZ103-
203.
OH...HEAT ADVISORY FROM NOON TO 8 PM EDT TUESDAY FOR OHZ001-002-004-
005-015-016.
MI...HEAT ADVISORY FROM NOON TO 8 PM EDT TUESDAY FOR MIZ078>081-177-
277.
MARINE...NONE.
DISCUSSION...ROLLER
AVIATION...MCD
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