991
FXUS63 KIWX 131729
AFDIWX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
129 PM EDT WED AUG 13 2025
KEY MESSAGES
- ISOLATED TO SCATTERED SHOWERS AND STORMS ARE POSSIBLE (20-35%
COVERAGE) THIS AFTERNOON MAINLY ALONG AND SOUTH OF US 24. A
FEW SHOWERS MAY ALSO DEVELOP DURING PEAK HEATING ALONG A LAKE
BREEZE.
- LESS HUMID AIR DROPS SOUTH BEHIND A COLD FRONT LATER TODAY INTO
TONIGHT, LEADING TO A PERIOD OF DRY WEATHER THROUGH FRIDAY.
- HEAT AND HUMIDITY RETURNS THIS WEEKEND WITH PEAK AFTERNOON HEAT
INDICES WELL INTO THE 90S.
- CHANCES OF STORMS RETURN LATER THIS WEEKEND INTO THE EARLY
PARTS OF NEXT WEEK.
DISCUSSION
ISSUED AT 330 AM EDT WED AUG 13 2025
SHOWERS AND STORMS HAVE LARGELY VACATED NORTHERN INDIANA AND
NORTHWEST OHIO TO THE EAST EARLY THIS MORNING AS A SOUTHERN STREAM
VORT MAX CONTINUES TO GET INGESTED NORTHEAST IN ADVANCE OF A
NORTHERN STREAM GREAT LAKES SHORT WAVE. AS MID/UPPER LEVEL CLOUDS
VACATE/THIN THIS MORNING, RESIDUAL NEAR SFC MOISTURE AND WEAK
GRADIENT SHOULD SUPPORT SOME PATCHY FOG DEVELOPMENT THROUGH 13Z,
WITH BEST CHANCES FOR AREAS WEST OF I-69 AND INTO SOUTH CENTRAL
LOWER MICHIGAN THAT RECEIVED THE GREATEST RAINFALL YESTERDAY.
LAGGING SFC COOL FRONT FROM WEST CENTRAL ILLINOIS INTO CENTRAL LOWER
MICHIGAN WILL SAG SOUTHEAST TODAY AND MAY ALLOW ISOLATED TO
SCATTERED SHOWERS, AND PERHAPS A FEW THUNDERSTORMS, TO DEVELOP.
NO SIGNIFICANT CHANGES MADE FROM PREVIOUS FORECAST WITH HIGHEST
CHANCE POPS IN THE 20-35% RANGE GENERALLY ALONG AND SOUTH OF US
24. INSTABILITY WILL BE MORE LIMITED TODAY WITH SLIGHTLY COOLER
LOW LEVELS AND MEAGER MID LEVEL LAPSE RATES. THIS SHOULD LEAD
TO MORE OF A "LONG, SKINNY" CAPE PROFILE WITH MAX MLCAPES ON THE
ORDER OF 1000-1500 J/KG ACROSS THE FAR SOUTHEAST. SHEAR
PROFILES WILL ALSO BE MORE LIMITED TODAY WITH THE PASSAGE OF THE
EARLY MORNING SHORT WAVE, LIKELY LEADING TO MORE OF PULSED
NATURE AND SHORT DURATION TO ANY STRONGER UPDRAFTS TODAY.
FARTHER TO THE NORTH, A FEW SHOWERS COULD DEVELOP ALONG A LAKE
BREEZE ENHANCED SECONDARY BOUNDARY. HOWEVER, INSTABILITY SHOULD
BE MORE LIMITED IN VICINITY OF THIS BOUNDARY. OVERALL, GIVEN
RATHER WEAK MID/UPPER LEVEL FORCING TODAY AND DIFFUSE LOW LEVEL
CONVERGENCE WITH FRONTAL ZONE, CONVECTION WILL BE MUCH MORE
LIMITED IN COVERAGE/STRENGTH COMPARED TO YESTERDAY. COOL AIR
ADVECTION THIS AFTERNOON SHOULD BE SOMEWHAT OFFSET BY SOME
POST FRONTAL MIXING TO SUPPORT HIGHS IN THE MID 80S MOST
LOCATIONS, WITH LESS HUMID CONDITIONS BUILDING FROM NORTH TO
SOUTH.
LOW LEVEL RIDGE AXIS BUILDS ACROSS THE WESTERN GREAT LAKES TONIGHT
WITH WEAK NORTHEAST FLOW. THIS COULD BE SUFFICIENT FOR SOME PATCHY
FOG DEVELOPMENT EARLY THURSDAY MORNING, BUT GIVEN DRY AIR ADVECTION
OVER THE PRECEDING 24 HOURS, THIS COULD BE VERY IN SHALLOW
NATURE IF IT DEVELOPS AND NOT QUITE WORTH A FORECAST MENTION AT
THIS TIME. OTHERWISE PLEASANT CONDITIONS ANTICIPATED FOR
THURSDAY AS SHORT WAVE UPPER RIDGING SHIFTS BACK ACROSS THE
WESTERN GREAT LAKES. GRADUAL MODIFICATION OF LOW LEVEL AIR MASS
AND GOOD INSOLATION SHOULD SUPPORT HIGHS IN THE MID 80S ONCE
AGAIN WITH HUMIDITY LEVELS REMAINING REASONABLE.
THE BROAD, WEAK UPSTREAM SHORT WAVE TROUGH ACROSS THE UPPER MIDWEST
WILL MAKE PROGRESS ACROSS THE GREAT LAKES REGION ON FRIDAY, BUT
RICHER LOW LEVEL MOISTURE SHOULD REMAIN ANCHORED BACK ACROSS THE MS
RIVER VALLEY. THIS LOW LEVEL THETA-E GRADIENT WILL BEGIN TO IMPINGE
ON THE AREA ONCE AGAIN LATE FRIDAY NIGHT INTO SATURDAY AND HAVE
MAINTAINED LOW CHANCE POPS GIVEN THIS FAIRLY SHARP INSTABILITY
GRADIENT.
MAIN FORECAST THEME FOR THIS WEEKEND INTO EARLY NEXT WEEK REMAINS
UNCHANGED WITH BUILDING HEAT AND HUMIDITY AND SEVERAL POTENTIAL
STORM CHANCES ALONG WHAT SHOULD BE A MAINTAINED INSTABILITY
GRADIENT. OVERALL BACKGROUND SHEAR STILL APPEARS ON THE SOMEWHAT
MARGINAL SIDE, BUT SOME UPSTREAM ENHANCEMENT TO CONVECTIVE SHORT
WAVES MAY ALLOW FOR A FEW PERIODS OF MORE ORGANIZED CLUSTERS OF
SHOWERS AND STORMS SOME TIME IN THE SATURDAY INTO MONDAY NIGHT
PERIOD. GIVEN POTENTIAL CONVECTIVE ENHANCEMENT OF UPSTREAM SHORT
WAVES, HAVE MAINTAINED BROAD BRUSH LOW CHANCE POPS WITH LOW
PREDICTABILITY IN MUCH POP DETAIL AT THIS FORECAST DISTANCE.
SUNDAY STILL APPEARS TO BE THE DAY OF POTENTIAL GREATEST HEAT
INDICES WITH GREATER CONFIDENCE IN MID LEVEL RIDGE STRENGTH FOR
THIS PERIOD. SOME CONVECTIVE DEBRIS CLOUDS MAY NEED TO BE
CONSIDERED BUT CONFIDENCE REMAINS ON THE HIGH SIDE FOR HEAT
INDICES WELL INTO THE 90S. CONSENSUS REMAINS IN MOST MEDIUM
RANGE GUIDANCE THAT ANOTHER FROPA WILL PROVIDE AT LEAST A
SHORTER PERIOD OF COOLER/LESS HUMID CONDITIONS TOWARD THE MIDDLE
OF NEXT WEEK.
AVIATION /18Z TAFS THROUGH 18Z THURSDAY/
ISSUED AT 125 PM EDT WED AUG 13 2025
STRATUS/FOG HAS FINALLY LIFTED AT BOTH SITES WITH DRIER AIR
SLOWLY WORKING IN FROM THE NW THROUGH THE PERIOD. CU WILL
PERSIST THROUGH SUNSET AT KFWA, BUT LAKE BREEZE MAY ALLOW KSBN
TO FULLY CLEAR OUT IN THE NEXT COUPLE OF HOURS. REGARDLESS,
CLOUD BASES ARE ABOVE 3000 FT SO NO CONCERNS FOR ANY FLIGHTS.
WHILE NOT REFLECTED IN THE TAFS, SOME PATCHY GROUND FOG IS
POSSIBLE LATER TONIGHT AS A SEMI MOIST BOUNDARY LAYER REMAINS IN
PLACE AND CROSSOVER TEMPS ARE EXCEEDED. FOR NOW HAVE LEFT ANY
MENTION OUT, BUT AT LEAST A MVFR TEMPO MAY NEED TO BE INTRODUCED
IN THE ROUGHLY 9 TO 13Z TIME FRAME.
IWX WATCHES/WARNINGS/ADVISORIES
IN...NONE.
OH...NONE.
MI...NONE.
MARINE...NONE.
DISCUSSION...MARSILI
AVIATION...FISHER
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