114
FXUS63 KIWX 100045
AFDIWX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
845 PM EDT SUN AUG 9 2026
KEY MESSAGES
- THERE REMAINS THE POTENTIAL FOR STRONG TO SEVERE THUNDERSTORMS
INTO TONIGHT. DAMAGING WINDS, FLASH FLOODING AND AN ISOLATED
TORNADO POSSIBLE.
- ADDITIONAL SEVERE THUNDERSTORMS AND FLOODING POSSIBLE MONDAY
AFTERNOON INTO MONDAY NIGHT.
- SEASONABLE TEMPERATURES ARE EXPECTED TO PERSIST.
UPDATE
ISSUED AT 828 PM EDT SUN AUG 9 2026
THE CONVECTIVE COMPLEX THAT WENT THROUGH THIS EVENING BROUGHT AN
AREA OF 2 TO 4 INCHES ESPECIALLY ALONG AND NORTH OF US-6 THIS
EVENING SETTING UP THE POTENTIAL FOR MORE EFFICIENT RUNOFF. AS A
LOW LEVEL JET SWINGS THROUGH, THERE ARE HINTS AT A SUBTLE
CONVECTIVELY ENHANCED VORT MAX FORMATION ACROSS THE AREA. THERE
IS STILL SOME QUESTION ABOUT IF THE COMPLEX CAN FORM GIVEN THE
AREA BEING RELATIVELY WORKED OVER TONIGHT FOLLOWING THE PREVIOUS
COMPLEX. WITH THE INCREASED WAA AND LARGE SCALE ASCENT COMING IN
ESPECIALLY AROUND 4 TO 6Z THERE IS SOME CONFIDENCE THAT
ADDITIONAL CONVECTION OCCURS. WPC HAS UP TO 2 ADDITIONAL INCHES
OF RAINFALL FORECAST OVER THE NEXT 12 HOURS AND WOULDN'T BE
SURPRISED TO SEE MORE THAN THAT IN AREAS WHERE CONVERGENCE
LINGERS ALLOWING FOR BACKBUILDING, TRAINING, AND POTENTIALLY
SLOW- MOVING CELLS. THERE'S LESS CONFIDENCE ON WHAT HAPPENS IN
NW, BUT THE JET AND THE LARGE SCALE ASCENT APPEARS TO DISSIPATE
LEADING ME TO BELIEVE IT STAYS ACROSS IN AND MI.
DISCUSSION
ISSUED AT 1243 PM EDT SUN AUG 9 2026
FOCUS REMAINS ON CONVECTIVE EVOLUTION AND INTENSITY LATE THIS
AFTERNOON INTO TONIGHT. SURFACE WARM FRONT IS ON SCHEDULE IN
REACHING TO NEAR THE MI BORDER DURING THIS TIME, ALLOWING FOR A
MUGGY AND UNSTABLE AIR MASS TO SETTLE IN FOR MOST LOCATIONS UNDER
PERTURBED WEST-NORTHWEST FLOW ALOFT.
THERE STILL APPEARS TO BE TWO WINDOWS FOR CONVECTION, THOUGH
THERE MIGHT NOT BE MUCH OF A BREAK BETWEEN THEM. THE FIRST
WINDOW IS LATE THIS AFTERNOON INTO EARLY THIS EVENING AS A SMALL
SCALE BOWING SEGMENT AND MCV (CURRENTLY NEAR MILWAUKEE)
CONTINUES EAST-SOUTHEAST INTERACTING WITH THE WARM FRONT AND
SUBSTANTIAL MUCAPE AXIS. NEW, SCATTERED, SFC BASED CELL GROWTH
APPEARS LIKELY ALONG ITS OUTFLOW IN THE VICINITY OF THE MI STATE
LINE 20-01Z. MARGINAL DEEP LAYER SHEAR PROFILES EXPECTED HERE
INITIALLY, ALONG WITH FORCING AND COLDER TEMPS ALOFT BYPASSING
NORTH MAY ALLOW WEAK CAPPING TO LIMIT COVERAGE AND INTENSITY
SOMEWHAT. THAT SAID, ~2000 J/KG OF MLCAPE AND THE CURRENT
FORWARD MOMENTUM OF THE CLUSTER COULD SUPPORT A DAMAGING WIND
AND NON-ZERO TORNADO THREAT INTO MAINLY SOUTHWEST MI AND FAR
NORTHERN IN DURING THIS TIME.
THE SECOND WINDOW COMES LATER THIS EVENING INTO THE OVERNIGHT HOURS
AS THE WARM FRONT BECOMES INVIGORATED BY AN INCOMING SMALL SCALE
IMPULSE AND DEEPER MOISTURE ADVECTION ON THE NOSE OF A ~40 KT
LOW LEVEL JET. THERE STILL MAY BE A DAMAGING WIND THREAT WITH
ANY BOWING SEGMENTS GIVEN THE LINGERING MUCAPE AND INCREASING
DEEP LAYER SHEAR, WITH AN ISOLATED TORNADO STILL NOT OUT OF THE
QUESTION. THE BIGGER CONCERN BY THIS TIME WITH BE THE FLASH
FLOOD POTENTIAL GIVEN THE POTENTIAL FOR TRAINING/BACKBUILDING
AND A DEEP WARM CLOUD LAYER WHEREVER THE COMPOSITE OUTFLOW
STALLS. THIS PLACEMENT WILL DEPEND ON HOW THE LATE AFTERNOON-
EARLY EVENING ACTIVITY EVOLVES (STRENGTH OF COLD POOL/OUTFLOW
UNCERTAIN). THIS WILL NEED TO BE CLOSELY MONITORED REGARDLESS
GIVEN THE HYBRID MADDOX/FRONTAL FLASH FLOOD LOOK TO THIS.
THIS PERIODICALLY STORMY PATTERN WILL LIKELY CONTINUE INTO AT LEAST
MONDAY AND TUESDAY AS SEVERAL SMALL SCALE PERTURBATIONS TRACK EAST-
SOUTHEAST IN THE VICINITY OF THE LINGERING FRONTAL ZONE AND
ASSOCIATED MUCAPE AXIS. FORECAST SPECIFICS ARE VERY UNCERTAIN IN
THIS KIND OF PATTERN (TAKE IT ONE DAY AT A TIME) GIVEN THE SUBTLE
NATURE TO THE FORCING MECHANISMS AND THE INFLUENCE OF PREVIOUS
CONVECTIVE EPISODES ON WHERE EXACTLY THE FRONTAL BOUNDARY SETS UP
FOR THE NEXT ROUND. AS FOR MONDAY, EXPECT A LULL MONDAY MORNING
BEFORE CHANCES FOR SEVERE STORMS INCREASE DURING THE AFTERNOON HOURS
AS STRONG DIURNAL BOUNDARY LAYER DESTABILIZATION DEVELOPS UNDER 30-
40 KTS OF 0-6 KM SHEAR. DAMAGING WINDS APPEAR TO THE PRIMARY THREAT,
WITH ANOTHER ROUND OF TRAINING STORMS AND FLASH POTENTIAL MONDAY
NIGHT AS THE LOW LEVEL JET RAMPS BACK UP.
TRENDS IN GUIDANCE CONTINUE TO FAVOR A TREND TOWARD DRIER/LESS
ACTIVE CONDITIONS MID TO LATE WEEK AS PREVIOUS EPISODES OF
CONVECTION HOPEFULLY FORCE THE EFFECTIVE BOUNDARY OFF TO THE
SOUTH.
AVIATION /00Z TAFS THROUGH 00Z TUESDAY/
ISSUED AT 747 PM EDT SUN AUG 9 2026
PREDOMINANTLY MVFR TO VFR CONDITIONS AT THE TERMINALS THIS
PERIOD, WITH POTENTIAL DROPS TO IFR CONDITIONS IN ANY HEAVIER
SHOWERS OR THUNDERSTORMS. THE MAIN SQUALL LINE HAS PASSED
THROUGH KFWA AND WILL CONTINUE EASTWARD THROUGH THE PERIOD.
ADDITIONAL SHOWERS AND STORMS ARE POSSIBLE AFTER A LULL LATE
THIS EVENING, WITH STORMS REFIRING WITH THE LLJ AND STALLED
BOUNDARY EXTENDING ACROSS THE AREA. MODEL GUIDANCE IS PRETTY
VARIABLE WITH THIS ACTIVITY TONIGHT, AND IT WAS TOUGH TO NARROW
DOWN EXACTLY WHERE AND WHEN THINGS DEVELOP. FOR NOW HAVE CHANCES
FOR SHOWERS AND STORMS REDEVELOPING AROUND 3-8Z TIME FRAME,
WITH BETTER POTENTIAL INITIALLY AT KSBN AND LATER AT KFWA.
IWX WATCHES/WARNINGS/ADVISORIES
IN...FLOOD WATCH FROM MIDNIGHT EDT /11 PM CDT/ TONIGHT THROUGH
MONDAY MORNING FOR INZ005>009-012>015-017-018-023>025-103-
104-116-203-204-216.
OH...NONE.
MI...FLOOD WATCH FROM MIDNIGHT EDT TONIGHT THROUGH MONDAY MORNING
FOR MIZ078>080-177-277.
MARINE...NONE.
UPDATE...ROLLER
DISCUSSION...STEINWEDEL
AVIATION...MCD
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