609
FXUS63 KIWX 261733
AFDIWX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
133 PM EDT THU JUN 26 2025
KEY MESSAGES
- HOT AND HUMID CONDITIONS WILL CAUSE HEAT INDICES TO RISE TO
NEAR 100 DEGREES TODAY, PROMPTING ANOTHER HEAT ADVISORY FOR
ALL AREAS.
- HIGHS WILL BE IN THE UPPER 80S TO AROUND 90 THROUGH MONDAY WITH
HEAT INDICES GENERALLY IN THE 90S TO AROUND 100 DEGREES.
- SCATTERED TO NUMEROUS MAINLY AFTERNOON AND EVENING
THUNDERSTORMS ARE FORECAST THROUGH MONDAY. SEVERE WEATHER
SHOULD BE LIMITED TO A LOCALLY STRONG TO SEVERE STORM WIND
GUST. LOCALLY HEAVY RAINFALL IN LIKELY WITH EVERY STORM.
DISCUSSION
ISSUED AT 257 AM EDT THU JUN 26 2025
THE UPPER LEVEL RIDGE REMAINED OVER THE OHIO VALLEY REGION EARLY
THIS MORNING. THE SUBSIDENCE AND WARMING ASSOCIATED WITH THIS SYSTEM
WAS CONTRIBUTING TO THE HOT AND HUMID CONDITION OVER THE PAST
SEVERAL DAYS OVER NORTHERN INDIANA AND SURROUNDING AREAS. THE
500 MB HEIGHT ANOMALY ASSOCIATED WITH THIS SYSTEM WAS STILL OVER
100 METERS ABOVE NORMAL. THE UPPER LEVEL RIDGE WILL GRADUALLY
WEAKEN AND SHOULD DRIFT EAST, ALLOWING A VERY SLOW COOLING TREND
THE NEXT FEW DAYS. CONCERN FOR THE LENGTHENING OF THE HEAT WAVE
THAT IS NOW BEGINNING THE 6TH DAY. HIGHS AT BOTH SOUTH BEND AND
FORT WAYNE HAVE BEEN BETWEEN 90 AND AND 94 DEGREES EVERY DAY OF
THIS HEAT WAVE SINCE SATURDAY. CAVEATS ON THE HOT SIDE INCLUDE
URBAN AREAS AND LOCALLY LOWER ELEVATIONS THAT MAY BE A FEW TO
SEVERAL DEGREES WARMER THAN SURROUNDING AREAS. NUMEROUS LOCATIONS
YESTERDAY RECORDED HEAT INDICES BETWEEN 105 AND 107. THE MOISTURE
DEPTH IN THE LOWER LAYERS WAS DEEP ENOUGH TO PREVENT MIXING OF
DRIER AIR ALOFT, ESPECIALLY WITH A WEAK CAP AT THE BASE OF A
WEAK SUBSIDENCE INVERSION. WE ARE PLANNING TO ISSUE A HEAT
ADVISORY FOR ALL OF OUR FORECAST AREA JUST FOR TODAY. HEAT
INDICES FRIDAY ARE MORE UNCERTAIN GIVEN THE LIKELIHOOD OF OUTFLOW
BOUNDARIES AND MORE WIDESPREAD RAIN-COOLED AIR.
AS FAR AS THUNDERSTORMS ARE CONCERNED, CONDITIONS TODAY SHOULD
BE VERY SIMILAR TO YESTERDAY WITH STORMS BEGINNING TO FORM AFTER
16Z (NOON EDT). COVERAGE OF STORMS SHOULD BE GREATER THAN
YESTERDAY GIVEN A DECREASE IN SUBSIDENCE AND GIVEN A WEAK AND
DIFFUSE FRONT ACROSS THE AREA. STORM MOVEMENT SHOULD BE SLOW TO
NON-EXISTANT, ESPECIALLY CONSIDERING MESO-BETA VELOCITY ELEMENTS
WITH VIRTUALLY NO MOVEMENT - LOCALLY HEAVY RAINFALL IS LIKELY
WITH EVERY THUNDERSTORM.
EXCEPT FOR RELATIVELY BRIEF COOLING SATURDAY IN THE WAKE OF A
WEAK COLD FRONT, THE HOT AND HUMID CONDITIONS WILL PERSIST
THROUGH MONDAY. ADDITIONAL HEAT HEADLINES ARE LIKELY.
AVIATION /18Z TAFS THROUGH 18Z FRIDAY/
ISSUED AT 133 PM EDT THU JUN 26 2025
TSTMS HAVE FIRED ACROSS SOUTHERN MI BETWEEN THE I94 AND I80
CORRIDORS WHILE MORE WIDELY SCTD ACROSS NRN IN.THIS TREND IS
EXPECTED TO CONTINUE THROUGH THE REST OF THE AFTN AND EVENING
PERIOD, SO WILL EMPHASIZE THE SBN TERMINAL SITE FOR CONVECTION
THROUGH 00Z. THUS FAR, THE STORMS HAVE REMAINED BELOW SVR
CRITERIA AS THEY ARE PULSE IN NATURE. THE FLOW IS PREDOMINATELY
SW FOR BOTH SITES AND WILL CARRY THIS INTO THE NIGHT HOURS THEN
WINDS TURN MORE SOUTHERLY OVERNIGHT AT KSBN. THE HEAT AND
ELEVATED HUMIDITY LEVELS CONTINUE FRIDAY AND COUPLED WITH THE
UPPER RIDGING WEAKENING, EXPECT A CONTINUATION OF TSTM
DEVELOPMENT WITH DAYTIME HEATING.
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...BROWN
AVIATION...MF
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