941
FXUS63 KIWX 011727
AFDIWX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
127 PM EDT TUE SEP 1 2026
KEY MESSAGES
- HEAT AND HUMIDITY CONTINUE THROUGH AT LEAST MIDWEEK WITH PEAK HEAT
INDICES AROUND 100 DEGREES.
- LOW CHANCES FOR SHOWERS AND STORMS (15-20%) NORTH OF I-80/I-90 TONIGHT
AND WEDNESDAY. IF AN ISOLATED STORM OR TWO DEVELOPS, IT COULD
PRODUCE GUSTY TO DAMAGING WINDS. LOW CONFIDENCE AT THIS TIME.
- 30-50% CHANCES FOR SHOWERS AND STORMS AREA-WIDE LATER IN THE
WEEK ON THURSDAY AND FRIDAY.
DISCUSSION
ISSUED AT 1250 PM EDT TUE SEP 1 2026
HAPPY SEPTEMBER 1ST AND START TO METEOROLOGICAL FALL! SUMMER SHOWS
NO SIGNS OF SLOWING DOWN AS WE START SEPTEMBER, WITH AN EXPANSIVE
UPPER LEVEL RIDGE OVERHEAD EXPECTED TO BRING HOT AND HUMID
CONDITIONS THROUGH MUCH OF THIS WEEK. A HEAT ADVISORY REMAINS IN
EFFECT FOR THE ENTIRE FORECAST AREA THROUGH 8 PM EDT WEDNESDAY. OUR
LATE SUMMER/EARLY FALL HEATWAVE BRINGS HIGH TEMPERATURES IN THE
UPPER 80S TO LOW 90S THROUGH AT LEAST MIDWEEK. WITH RETURN FLOW OFF
OF THE GULF DUE TO SURFACE HIGH PRESSURE CENTERED OVER THE SOUTHEAST
CONUS, HIGH HUMIDITY IS EXPECTED TO PERSIST THROUGH AT LEAST
MIDWEEK. DESPITE THE UNEXPECTED SHOWERS AND STORMS THIS MORNING,
CLEARING IS ALREADY ONGOING THIS AFTERNOON PER VISIBLE
SATELLITE IMAGERY, WHICH WILL ALLOW FOR TEMPERATURES TO CLIMB
INTO AT LEAST THE MID TO UPPER 80S FOR HIGHS TODAY SLIGHTLY
WARMER WEDNESDAY WITH HIGHS IN THE LOW 90S WITH THE PEAK OF THE
RIDGE OVERHEAD. HEAT INDICES ARE EXPECTED TO BE AT OR SLIGHTLY
ABOVE 100 DEGREES, ESPECIALLY THIS AFTERNOON AND AGAIN WEDNESDAY
AFTERNOON. THERE WILL BE MINIMAL RELIEF OVERNIGHT WITH NEAR
RECORD LOWS IN THE MID 70S. HEAT INDICES AROUND 100 DEGREES MAY
PERSIST ALONG AND SOUTH OF US 30 INTO THURSDAY, SO THE HEAT
ADVISORY MAY NEED EXTENDED IN A FUTURE FORECAST UPDATE.
CONSIDERABLE UNCERTAINTY REMAINS IN REGARDS TO RAIN AND STORMS
CHANCES THIS WEEK. ALL MODELS HAVE STRUGGLED WITH THIS PATTERN
OVER THE PAST FEW DAYS; A MAJORITY OF RECENT RUNS OF HI-RES
GUIDANCE HAVE BEEN MISLEADING, KEEPING THE UPPER LEVEL RIDGE
WELL TO OUR NORTH WHEREAS IN REALITY, OUR AREA (ESPECIALLY THE
NORTHERN HALF) HAS BEEN ON THAT PERIPHERY AS WELL. WE HAD
SCATTERED SHOWERS AND STORMS IN THE VICINITY OF THE US 30
CORRIDOR THIS MORNING AND NONE OF THE MODELS SHOWED ANYTHING
OCCURING. MODELS HAVE BEEN TAKING THE RAIN/STORM CHANCES NORTH
OUT OF OUR AREA, WHICH HAS CREATED CHALLENGES AND CONSIDERABLE
UNCERTAINTY IN REGARDS TO WHAT TO DO WITH POPS OVER THE NEXT FEW
DAYS. THE NBM WANTS TO HOLD OFF ON ANY RAIN FOR OUR LOWER
MICHIGAN COUNTIES UNTIL EARLY THURSDAY AT THE EARLIEST. HOWEVER,
I CANNOT RULE OUT AT LEAST ISOLATED SHOWER/STORM DEVELOPMENT IN
OUR FORECAST AREA (ESPECIALLY NORTH OF I-80/I-90) TONIGHT AND
WEDNESDAY, WHERE I HAVE ADDED BROAD 15-20% POPS. SHOULD ANY
STORMS DEVELOP, HEAT AND HUMIDITY SHOULD FUEL MLCAPE VALUES OF
UP TO 3000-4000 J/KG AND STEEPING LOW LEVEL LAPSE RATES. SPC
DOES HAVE AT LEAST THE NORTHERN/NORTHEAST HALF OF OUR AREA IN A
MARGINAL RISK EACH DAY THROUGH THURSDAY WITH THE MAIN RISK BEING
GUSTY TO DAMAGING WINDS. CONFIDENCE IS LOW GIVEN THE
AFOREMENTIONED UNCERTAINTY WITH MODELS. BETTER CHANCES (30-50%)
FOR RAIN/STORMS AREA- WIDE ARE IN THE FORECAST FOR LATER
THURSDAY INTO FRIDAY AS THE UPPER LEVEL RIDGE GRADUALLY
FLATTENS, ALTHOUGH UNCERTAINTY STILL REMAINS IN THE FORECAST
SEVERAL DAYS OUT GIVEN THE RECENT UNRELIABLE MODEL GUIDANCE. OUR
FAR SOUTHWEST COUNTIES HAVE THE BEST CHANCES FOR REMAINING
COMPLETELY DRY THIS WEEK WITH HEAT AND HUMIDITY CONTINUING
THROUGH LATE IN THE WEEK. BY THE WEEKEND, TEMPERATURES TREND
CLOSER TOWARDS NORMAL WITH HIGHS IN THE LOW 80S.
AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/
ISSUED AT 112 PM EDT TUE SEP 1 2026
NORTHERN INDIANA IS CAUGHT BETWEEN STRONG HIGH PRESSURE TO THE
SOUTH AND A DEEP LOW OVER CENTRAL CANADA. SO WITH MOIST ZONAL
FLOW ACROSS THE REGION, TRANSIENT WEAK SHORTWAVES WILL CONTINUE
TO BRING SHOWERS AND THUNDERSTORMS THAT ARE NOT BEING DEPICTED
WELL BY THE MODELS. CURRENTLY, CONVECTION IS MAINLY OVER SOUTHWEST
LOWER MICHIGAN AND IS EXPECTED TO REMAIN NORTH OF SBN. THAT
SAID, BOTH TERMINALS ARE FORECAST TO REMAIN DRY AND VFR THROUGH
THE NEXT 24 HOURS WITH MAINLY SCT-BKN HIGH CLOUDS AND SOUTHWEST
WINDS 5-10 KTS. SBN COULD STILL SEE SOME MORE ACTIVITY THIS
EVENING, BUT CONFIDENCE IS LOW. HAVE BETTER CONFIDENCE THAT FWA
WILL STAY DRY, ALTHOUGH THERE IS A CHANCE FOR SOME MORNING HAZE
ON WEDNESDAY.
IWX WATCHES/WARNINGS/ADVISORIES
IN...HEAT ADVISORY UNTIL 8 PM EDT /7 PM CDT/ WEDNESDAY 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 WEDNESDAY FOR OHZ001-002-004-005-
015-016-024-025.
MI...HEAT ADVISORY UNTIL 8 PM EDT WEDNESDAY FOR MIZ078>081-177-277.
MARINE...NONE.
DISCUSSION...JOHNSON
AVIATION...COBB
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