092
FXUS63 KIWX 201156
AFDIWX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
756 AM EDT SUN SEP 20 2026
KEY MESSAGES
- PERIODS OF RAIN AND CHANCES FOR EMBEDDED THUNDER LINGERING
INTO TODAY AND TONIGHT. LOCALIZED HEAVY RAINFALL RATES AND
FLOODING WILL REMAIN POSSIBLE.
- A DRIER PATTERN SETS UP NEXT WEEK, THOUGH LIGHT SHOWERS AND
DRIZZLE MAY LINGER INTO MONDAY AND TUESDAY.
- COOLER NEXT WEEK WITH HIGHS ONLY IN THE 60S MONDAY THROUGH
WEDNESDAY.
DISCUSSION
ISSUED AT 246 AM EDT SUN SEP 20 2026
AN UPSTREAM SHORTWAVE WILL TRACK EAST INTO THE AREA TODAY CONTINUING
TO PROVIDE A STEADY FEED OF MOIST ISENTROPIC ASCENT INTO A LINGERING
WEST TO EAST ORIENTED BAROCLINIC ZONE. THIS WILL KEEP AREAS OF RAIN,
LOW CLOUDS AND DRIZZLE AROUND FOR MOST OF TODAY INTO THIS EVENING.
THE SAVING GRACE REGARDING FLOODING SO FAR HAS BEEN LACKING RAINFALL
RATES WITH THE MAIN MUCAPE AXIS REMAINING OFF TO THE SOUTHWEST. THIS
MAY CHANGE HOWEVER TODAY GIVEN RADAR TRENDS OVER NORTHERN IL
ASSOCIATED WITH THE INCOMING SHORTWAVE THAT HINT AT AN UPTICK IN
MORE ROBUST RAIN AND CHANCES FOR EMBEDDED THUNDER, WITH
MODEL/OB/RADAR TRENDS POINTING TO AREAS MAINLY ALONG AND NORTH OF
THE US 30 CORRIDOR THIS MORNING FOR HEAVIER RAINFALL RATES AND FLOOD
IMPACTS. A SLIGHT SHIFT MORE INTO THE SOUTHERN HALF OF THE FORECAST
AREA THEN POSSIBLE THIS AFTERNOON-EVENING WHERE DIFFERENTIAL HEATING
NEAR THE SFC PORTION OF THE FRONT LIKELY PRODUCES SOME HEAVIER
CONVECTIVE ELEMENTS IN AREAS THAT CANNOT TAKE ON ANY MORE RAIN. HAVE
OPTED TO EXTEND THE FLOOD WATCH THROUGH 18Z TODAY, WITH FURTHER
EXTENSION POTENTIALLY NEEDED.
THE STORY THEN FOR MUCH OF NEXT WEEK WILL TURN TO A PERSISTENT FEED
OF DRIER, COOLER EAST-NORTHEAST FLOW ON THE SOUTHERN FRINGE OF HIGH
PRESSURE LAYING OUT ACROSS THE NORTHERN GREAT LAKES. THE MAIN
MOISTURE AXIS SHIFTS SOUTH OF THE AREA MONDAY INTO TUESDAY IN THIS
REGIME. HOWEVER, TRAILING SHORTWAVE ENERGY IN BROAD CYCLONIC FLOW
ALOFT MAY SUPPORT A FEW FLARE UPS IN SHOWER/DRIZZLE ACTIVITY,
ESPECIALLY ON MONDAY SOUTH OF US 30.
AVIATION /12Z TAFS THROUGH 12Z MONDAY/
ISSUED AT 748 AM EDT SUN SEP 20 2026
AN INSTABILITY GRADIENT HAS GRADUALLY LIFTED BACK NORTHWARD THIS
MORNING AND SHOULD REMAIN ANCHORED ACROSS NORTHERN INDIANA
THROUGH THE EARLY EVENING HOURS. CLUSTERS OF SHOWERS AND
THUNDERSTORMS HAVE FORMED ALONG THIS INSTABILITY GRADIENT WITH
THE MOST PROMINENT AREA EXPECTED TO AFFECT KFWA BETWEEN 13 AND
14Z THIS MORNING. SOME QUESTION AOS TO COVERAGE OF SHOWERS AND
THUNDERSTORMS LATE MORNING INTO EARLY AFTERNOON, BUT WATER
VAPOR/IR IMAGERY DOES SUGGEST ANOTHER UPSTREAM WAVE APPROACHING
EASTERN IOWA AND NORTHWEST ILLINOIS THAT WILL LIKELY AUGMENT
PRECIP COVERAGE LATER THIS AFTERNOON AND EVENING. LARGE SCALE
FRONTAL FORCING WILL ALSO INCREASE THIS AFTERNOON WHICH WILL
LIKELY CAUSE RENEWED COVERAGE OF SHOWERS/EMBEDDED STORMS. IFR OR
BRIEFLY IMPROVED CIGS IN STRONGER CONVECTIVE ELEMENTS WILL
CONTINUE THROUGH MUCH OF THE DAY, WITH GREATER CONFIDENCE IN
IMPROVEMENT NOT UNTIL LATER THIS EVENING.
IWX WATCHES/WARNINGS/ADVISORIES
IN...FLOOD WATCH UNTIL 2 PM EDT /1 PM CDT/ THIS AFTERNOON FOR
INZ005>009-012-014-015-017-018-023>027-032>034-103-104-
116-203-204-216.
OH...FLOOD WATCH UNTIL 2 PM EDT THIS AFTERNOON FOR OHZ015-024.
MI...FLOOD WATCH UNTIL 2 PM EDT THIS AFTERNOON FOR MIZ078>080-177-
277.
MARINE...NONE.
DISCUSSION...STEINWEDEL
AVIATION...MARSILI
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