575
FXUS63 KIWX 151111
AFDIWX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
711 AM EDT SAT AUG 15 2026
KEY MESSAGES
- MULTIPLE ROUNDS OF STORMS ARE EXPECTED THROUGH SUNDAY
AFTERNOON. THE GREATEST SEVERE RISK WILL BE LATE THIS
AFTERNOON FOR AREAS EAST OF I-69.
- HEAVY RAIN WILL BE A CONCERN WITH ANY THUNDERSTORMS AND COULD
CAUSE RENEWED FLOODING FOR AREAS SOUTH OF US-30 THAT ALREADY
SAW HEAVY RAIN THIS WEEK. A FLOOD WATCH REMAINS IN EFFECT
THROUGH TONIGHT THERE.
- DRY CONDITIONS RETURN SUNDAY NIGHT AND PERSIST THROUGH
TUESDAY.
DISCUSSION
ISSUED AT 205 AM EDT SAT AUG 15 2026
UNFORTUNATELY, THE NEXT 36 HOURS WILL REMAIN ACTIVE WITH MULTIPLE
WAVES OF CONVECTION, EACH ONE IMPACTING THE NEXT TO SOME DEGREE AND
LEADING TO AN OVERALL LOW CONFIDENCE FORECAST. THE FIRST ROUND IS
ALREADY LIGHTING UP OVER CENTRAL IL. WATER VAPOR IMAGERY SHOWS A
PAIR OF ROBUST MCV'S OVER THE CENTRAL PLAINS AND DOWNSTREAM, THE LLJ
IS RAMPING UP ONCE AGAIN WITH A FIRE HOSE OF LOW LEVEL THETA-E
ADVECTION (850MB DEWPOINTS NEAR 20C OVER CENTRAL IL). THIS ACTIVITY
WILL CONTINUE TO PROPAGATE EASTWARD THROUGH THE MORNING. THE
ENVIRONMENT CURRENTLY OVER OUR CWA IS NOT FAVORABLE FOR DEEP, MOIST
CONVECTION GIVEN A STEADY FEED OF LIGHT EASTERLY LOW LEVEL FLOW
LOCALLY. OF COURSE THE LLJ/MOISTURE ADVECTION WILL MODULATE THIS TO
SOME DEGREE BUT THE LLJ WILL BE IN A WEAKENING STATE AFTER SUNRISE
AND MIDLEVEL LAPSE RATES ARE VERY MEAGER IN OUR AREA. DO EXPECT
STORMS TO IMPACT OUR CWA ROUGHLY 11-17Z BUT SHOULD WEAKEN WITH TIME
AND E/NE EXTENT. SOME GUSTY WINDS CAN'T BE RULED OUT IN THIS
SCENARIO, ESPECIALLY IN OUR SW ZONES, BUT OVERALL THE SEVERE RISK
LOOKS LOW IN OUR AREA WITH ROUND 1. WHILE THESE STORMS ARE EXPECTED
TO REMAIN MORE PROGRESSIVE THAN RECENT DAYS, THE VERY MOIST
ENVIRONMENT COULD STILL SUPPORT BRIEF HEAVY RAIN AND OUR SOUTHERN
COUNTIES REALLY CAN'T TAKE ANYMORE AT THIS POINT SO FLOODING WILL BE
A CONCERN. NO CHANGES TO THE FLOOD WATCH PLANNED AT THIS TIME.
ONE POSSIBLE SCENARIO TO WATCH FOR THOUGH IS A DELAYED ARRIVAL TIED
TO A MORE ROBUST MCV AS SUGGESTED BY A FEW RUNS OF THE HRRR. IF THIS
OCCURS, AND CONVECTION CAN GET MORE ROOTED TO THE SURFACE, THEN
ROUND 1 COULD FEATURE A HIGHER SEVERE RISK (AS WELL AS GREATER HEAVY
RAIN/FLOODING CONCERNS) IN THE 15-18Z WINDOW. WHILE THIS REMAINS A
POSSIBILITY, IT IS NOT THE PREFERRED SOLUTION AT THIS TIME DUE TO
THE POOR INITIALIZATION SEEN IN THOSE RUNS OF THE HRRR AND THE
OVERALL SYNOPTIC AND MESOSCALE PICTURE AT THIS POINT.
UNFORTUNATELY, ROUND 2 SLATED FOR LATE AFTERNOON/EVENING WILL DEPEND
LARGELY ON THE EXACT EVOLUTION OF THE FIRST ROUND AND ANY POTENTIAL
SUBTLE MCV'S EJECTING OUT OF UPSTREAM CONVECTION. AN EARLIER/WEAKER
ROUND 1 INCREASES THE CONCERN FOR ROUND 2 AND VICE VERSA. IF THERE
IS SUFFICIENT RECOVERY TIME, MLCAPE VALUES COULD REBUILD TO OVER
1000 J/KG AND 40 KT WINDS AT 700MB YIELD MODERATE 0-3KM SHEAR
PROFILES. ORGANIZED CONVECTION WILL BE POSSIBLE IN THIS SCENARIO
WITH THE BEST CHANCES LIKELY EAST OF I-69. WILL HAVE TO WATCH THE
MESOSCALE ENVIRONMENT CLOSELY TODAY AS MODELS HINT THERE COULD BE
GREATER THAN 200 M2/S2 OF 0-1KM HELICITY IN THE VICINITY OF THIS
WARM FRONT, VERY LOW LCL'S, AND JUST ENOUGH INSTABILITY TO YIELD A
TORNADO THREAT. THAT IS OF COURSE HIGHLY DEPENDENT ON HOW MORNING
CONVECTION PLAYS OUT AND IT IS EQUALLY PLAUSIBLE BOTH INSTABILITY
AND/OR MIDLEVEL FORCING FAIL, RESULTING IN A COMPLETE NULL EVENT.
VERY CHALLENGING SCENARIO AND REQUIRES CLOSE MONITORING TODAY.
ADDITIONAL STORMS THEN EXPECTED LATE TONIGHT/SUNDAY MORNING AND
POSSIBLY AGAIN SUNDAY AFTERNOON. THE STORY HERE IS MUCH THE SAME
WITH UNCERTAINTIES COMPOUNDING FOR EACH SUCCESSIVE WAVE OF
CONVECTION. CURRENT BEST GUESS IS THAT ANOTHER NOCTURNAL
STRENGTHENING OF THE LLJ WILL FEATURE MORE STORMS WITH MAINLY A
HEAVY RAIN THREAT ROUGHLY 08-14Z. AT THIS POINT THOUGH, SUN AM
CONVECTION LOOKS WEAKER AND MORE SCATTERED THAN TONIGHT (DRIVEN MORE
BY APPROACHING MIDLEVEL TROUGH/COLD FRONT THAN VERY STRONG MOISTURE
FLUX CONVERGENCE). HOWEVER, MUCH LIKE TODAY IT WON'T TAKE MUCH TO
CAUSE FLOODING IN OUR SOUTH AND THE FLOOD WATCH MAY NEED TO BE
EXTENDED THROUGH SUN MORNING TO ACCOUNT FOR THIS. COLD FRONT FINALLY
PASSES LATE SUN AFTERNOON. EXACT TIMING AND DEGREE OF INSTABILITY
RECOVERY REMAIN VERY MUCH IN QUESTION, BUT SOME STRONG STORMS MAY
AGAIN BE POSSIBLE, ESPECIALLY SOUTH OF US-24.
RELIEF FINALLY ARRIVES SUN NIGHT WITH DRY CONDITIONS THROUGH TUE.
ANOTHER COLD FRONT PASSES ON WED BUT THIS SHOULD BE QUICK-HITTING
AND MOST GUIDANCE SUGGESTS TRANQUIL WEATHER LATE NEXT WEEK INTO NEXT
WEEKEND.
AVIATION /12Z TAFS THROUGH 12Z SUNDAY/
ISSUED AT 707 AM EDT SAT AUG 15 2026
AREA OF RAIN AND EMBEDDED THUNDERSTORMS IS SPREADING EAST THIS
MORNING, WITH SOME NORTHWARD EXPANSION NOTED. OVERALL, HIGH
CONFIDENCE IN DETERIORATING FLIGHT CONDITIONS THIS MORNING.
FOLLOWING THIS MORNING'S PERIOD OF RAIN WE'LL BE MONITORING FOR
REDEVELOPMENT IN THE VICINITY OF KFWA IN THE WINDOW OF 21-00Z.
THIS ROUND WILL BE HIGHLY CONTINGENT ON HOW THIS MORNING
PROGRESSES, SO, HAVE STAYED CLOSE TO THE EXISTING TAF.
AT THE END OF THIS PERIOD, YET ANOTHER DISTURBANCE TRACKS IN
FROM ILLINOIS.
IWX WATCHES/WARNINGS/ADVISORIES
IN...FLOOD WATCH THROUGH THIS EVENING FOR INZ012-013-015-020-
022>027-032>034.
OH...FLOOD WATCH FROM 11 AM EDT THIS MORNING THROUGH THIS EVENING
FOR OHZ024-025.
MI...NONE.
MARINE...NONE.
DISCUSSION...AGD
AVIATION...BROWN
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