181
FXUS63 KIWX 121735
AFDIWX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
135 PM EDT TUE AUG 12 2025
KEY MESSAGES
- SCATTERED TO NUMEROUS SHOWERS AND STORMS LATE THIS AFTERNOON
INTO THIS EVENING. THE STRONGEST STORMS WILL BE CAPABLE OF
PRODUCING LOCALLY HEAVY RAINFALL AND ISOLATED WIND GUSTS IN
EXCESS OF 50 MPH.
- A FEW SHOWERS AND STORMS MAY REDEVELOP ALONG A COLD FRONT WEDNESDAY
AFTERNOON, BEST CHANCES (20-40%) ALONG AND SOUTH OF US 24.
- HEAT AND HUMIDITY RETURNS THIS WEEKEND WITH PEAK AFTERNOON HEAT
INDICES WELL INTO THE 90S.
DISCUSSION
ISSUED AT 135 PM EDT TUE AUG 12 2025
A MOIST AND DIURNALLY DESTABILIZING THERMODYNAMIC ENVIRONMENT
CONTINUES TO APPEAR SUPPORTIVE OF SCATTERED TO NUMEROUS SHOWERS AND
STORMS AS WEAK HEIGHT FALLS/TROUGHING OVERSPREAD. AREAS OF
CONVERGENCE AND INSTABILITY GRADIENTS WILL BE THE LOCATIONS WHERE
CONVECTION LIKELY FIRES. LATEST REGIONAL MOSAIC RADAR AND HRRR
TRENDS HINT AT WIDELY SCATTERED CONVECTION FOR MOST THIS AFTERNOON
INTO THIS EVENING NEAR BOUNDARIES AND WITH SUBTLE MID LEVEL
IMPULSES, WITH A MORE ORGANIZED CLUSTER OF STORMS LIKELY TRACKING
EAST INTO AREAS MAINLY WEST OF INTERSTATE 69 LATE THIS
AFTERNOON INTO THIS EVENING IN ADVANCE OF A COLD FRONT. LOCALLY
HEAVY RAINFALL APPEARS TO BE THE PRIMARY THREAT GIVEN THE DEEP
MOIST CLOUD LAYER, THOUGH MORE ROBUST, PRECIPITATION LOADED
CORES COULD ALSO PRODUCE ISOLATED WIND GUSTS IN EXCESS OF 50
MPH GIVEN A FAVORABLE DCAPE PROFILE.
AN UPPER TROUGH TRACKING EAST THROUGH THE GREAT LAKES WILL FORCE THE
PRIMARY COLD FRONT SOUTHEAST INTO THE AREA OVERNIGHT INTO WEDNESDAY
MORNING, WITH THIS BOUNDARY POTENTIALLY GETTING HUNG UP NEAR OR JUST
OF THE US 24 CORRIDOR BY PEAK HEATING TOMORROW. LINGERING HUMIDITY
AND LOW CHANCES FOR A FEW SHOWERS/STORMS POSSIBLE IF THE BOUNDARY
LAYER SUFFICIENTLY RECOVERS. REGARDLESS, LOSS OF DEEPER MOISTURE AND
FORCING PRECLUDES ANYTHING MORE THAN A 20-30% POP, WITH DRIER AIR
FINALLY FILTERING WITH PLEASANT WEATHER THURSDAY INTO FRIDAY.
THE HEAT AND HUMIDITY THAT HAS BEEN A COMMON THEME THIS SUMMER
RETURNS THIS WEEKEND AS THE PERSISTENT SUBTROPICAL RIDGE FLEXES
NORTHEASTWARD TOWARD THE LOWER GREAT LAKES. MODELS DIFFER ON HOW
QUICKLY THIS FEATURE RETROGRADES BACK WEST AS A SERIES OF RING OF
FIRE CONVECTIVE COMPLEXES ROLL THROUGH ITS NORTHERN FRINGES. THESE
MCS'S WILL NEED MONITORING, PARTICULARLY SUNDAY INTO EARLY NEXT WEEK.
AVIATION /18Z TAFS THROUGH 18Z WEDNESDAY/
ISSUED AT 135 PM EDT TUE AUG 12 2025
REMNANT OUTFLOW BOUNDARIES AND WEAK AREAS OF VORTICITY MOVED THROUGH
OUR NORTHWESTERN AREAS THIS MORNING AND THERE IS SOME CHANCE OF AN
EASTWARD PUSH OF THIS FORCING FOR THE AFTERNOON. HI-RES MODELS DID
NOT CATCH ONTO MORNING CONVECTION WITHIN ADVANCEMENT OF HIGHER THETA-
E AIRMASS THAT CAUSED WEAK SHOWERS AND STORMS, BUT THESE DID DIE ON
OUR WESTERN EDGE OF THE FORECAST AREA. WITHIN WEAK AREA OF
INSTABILITY, THERE COULD BE GROWTH TO THIS AREA, BUT EXTENT OF
UPSCALE GROWTH IS UNCERTAIN IN ANY DIRECTION ESPECIALLY GIVEN EXTENT
OF RIDGING OVERHEAD AND LINGERING DRY AIR FROM RECENT EXTENDED
PERIOD OF DRY AIR. WARM ADVECTION PRECIP APPEARS TO BE CREATING MVFR
FLIGHT CONDITIONS UNDERNEATH IT, BUT STILL, IT'S UNCERTAIN IF THAT
ENDS UP HITTING SBN OR FWA. AT THIS POINT, FEEL IT'S MOST PRUDENT TO
KEEP GROUPS FOR THIS OUT OF THE TAFS UNTIL SOMETHING ALLOWS FOR MORE
CONFIDENCE. AMENDMENTS WILL LIKELY BE NECESSARY. ANOTHER AREA OF
RAIN AND PERHAPS SOME THUNDERSTORMS ARRIVES BETWEEN 00Z AND 06Z AS
THETA-E AXIS SLIDES NORTHWARD. THIS COULD PROVIDE ANOTHER
OPPORTUNITY FOR LOWER FLIGHT CONDITIONS GIVEN COVERAGE OF RAIN AND
POSSIBLE INTENSITY OF SHOWERS/STORMS, BUT IT'S UNCERTAIN IF IT WILL
HIT SBN OR STAY NORTH OF IT. FEEL IT IS MOST PRUDENT TO USE PROB30
GROUP FOR THAT. MOIST AXIS THEN ADVANCES EASTWARD LATER TUESDAY
NIGHT INTO WEDNESDAY MORNING WHICH STILL PROVIDES MORE OPPORTUNITIES
FOR RAIN AT SBN. HOWEVER, FLIGHT CONDITIONS DO NOT APPEAR TO BE
AFFECTED IN A PREVAILING THREAT AND DON'T HAVE ENOUGH CONFIDENCE
GIVEN MODEL UNCERTAINTY TO PUT THIS THREAT IN EITHER. STILL EXPECT
SOUTHWEST WIND TRAJECTORIES WITH PERIODS OF AROUND 10 KTS SUSTAINED
DURING PEAK HEATING TIMES.
IWX WATCHES/WARNINGS/ADVISORIES
IN...NONE.
OH...NONE.
MI...NONE.
MARINE...NONE.
DISCUSSION...STEINWEDEL
AVIATION...ROLLER
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