017
FXUS63 KIWX 031039
AFDIWX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
639 AM EDT FRI JUL 3 2026
KEY MESSAGES
- THE EXTREME HEAT WARNING CONTINUES THROUGH THIS EVENING ACROSS
NORTHWEST OHIO, ALONG WITH PORTIONS OF NORTHERN INDIANA MAINLY
EAST OF I-69 AND SOUTH OF US 24. A HEAT ADVISORY IS IS EFFECT
ELSEWHERE. HEAT INDICES WILL RANGE FROM THE UPPER 90S TO
AROUND 105 (HIGHEST IN THE WARNING AREA).
- THERE IS A SLIGHT RISK (LEVEL 2 OF 5) FOR SEVERE WEATHER THIS
AFTERNOON INTO THIS EVENING, WITH THE GREATEST POTENTIAL OF
SEVERE STORMS FROM 3PM EDT TO 11PM EDT. DAMAGING WIND GUSTS,
LIGHTNING, AND LOCALLY HEAVY RAIN ARE THE MAIN THREATS, BUT
ISOLATED LARGE HAIL CANNOT BE RULED OUT.
- HOT AND HUMID FOR THE 4TH OF JULY WITH UP TO 70% CHANCES FOR
SHOWERS AND STORMS. THERE IS A MARGINAL RISK (LEVEL 1 OF 5)
FOR SEVERE WEATHER. ISOLATED STORMS ARE MOST LIKELY FROM 2PM
EDT TO 11PM EDT. WITH ISOLATED DAMAGING WIND GUSTS, HEAVY
RAIN, AND LIGHTNING AS THE MAIN THREATS. AN ISOLATED SEVERE
STORM MAY EXIST ONCE AGAIN SUNDAY AFTERNOON, BUT CONFIDENCE IS
LOWER.
DISCUSSION
ISSUED AT 357 AM EDT FRI JUL 3 2026
OUTFLOW DOMINATED CONVECTIVE COMPLEX IS PROGRESSING ACROSS NORTHWEST
INDIANA INTO SOUTHWEST LOWER MICHIGAN EARLY THIS MORNING. A FEW
OUTFLOW BOUNDARIES HAVE PASSED ACROSS NORTHWEST PORTIONS OF THE
FORECAST AREA EARLY THIS MORNING. THIS OUTFLOW IS HELPING TO SUSTAIN
CONVECTION EARLY THIS MORNING AS IT APPROACHES THE SOUTH BEND AREA,
ALONG WITH A POCKET OF ENHANCED 30-40 KNOTS OF EFFECTIVE SHEAR VIA
SOME CONVECTIVE ENHANCEMENT OF THE SHORT WAVE. THIS CONVECTIVE
COMPLEX DOES STILL HAVE A 2500 J/KG MLCAPE AXIS TO WORK WITH ACROSS
FAR NORTHERN IN/SOUTHERN LOWER MI THIS MORNING, ALTHOUGH SOME WEAK
DOWNSTREAM MLCIN WILL CONTINUE TO DEVELOP THROUGH THE REMAINDER OF
THE OVERNIGHT. FORCING WITH THE OUTFLOW WILL LIKELY BE ENOUGH TO
OVERCOME THIS WEAK CIN HOWEVER, WHICH COULD VERY WELL ALLOW FOR
EASTWARD MAINTENANCE OF THE CONVECTION THROUGH MOST OF FAR NORTHERN
INDIANA AND SOUTHER LOWER MICHIGAN. THESE STORMS ARE NOT EXPECTED TO
BE SEVERE THIS MORNING WITH A POSSIBILITY OF SOME ISOLATED
GUSTS TO 40 TO 50 MPH AND BRIEF HEAVY RAINFALL. 0-3KM SHEAR
VECTORS ARE SOMEWHAT IMPRESSIVE (SOUTHWEST AROUND 30 KNOTS)
WHICH COULD POSE SOME CONCERN FOR BRIEF MESOVORT, BUT INCREASING
ELEVATED/OUTFLOW DOMINANT NATURE OF THIS COMPLEX SHOULD LESSEN
SEVERE POTENTIAL THIS MORNING.
THE AM STORMS WILL LEAVE BEHIND AN OUTFLOW BOUNDARY THAT COULD SERVE
AS A FOCUS FOR ISOLATED-SCATTERED STORM DEVELOPMENT AFTER 18Z THIS
AFTERNOON, ALTHOUGH BULK OF CAM GUIDANCE DOES STILL MAINTAIN LATER
TIMING TOWARD 20Z AND BEYOND AS ANOTHER CONVECTIVELY ENHANCED SHORT
WAVE EMERGES FROM IA/CENTRAL PLAINS. IMPRESSIVE INSTABILITY
PROFILES (MLCAPES ON ORDER OF 2500-3000 J/KG) WILL BE IN PLACE
THIS AFTERNOON AND APPROACH OF THIS SHORT WAVE TOWARD EVENING
COULD ALSO ENHANCE CONVECTION ALONG REMNANT OUTFLOWS. SHEAR
PROFILES WILL BE LESS FAVORABLE SEVERE WEATHER INGREDIENT TODAY,
WITH SHEAR PROFILES GRADUALLY WANING THIS MORNING WITH
DEPARTURE OF AM VORT MAX. ONE THING THAT MAY NEED TO BE WATCHED
TODAY IS THE POTENTIAL FOR A FAVORABLE WET MICROBURST
ENVIRONMENT GIVEN HIGH CAPES AND STEEP 0- 3KM LAPSE RATES. SOME
RELATIVELY DRIER MID LEVEL THETA-E AIR MAY ALSO BE WORKING ALONG
NORTHWEST PERIPHERY OF THE SUPPRESSED MID LEVEL RIDGE THAT
COULD ENHANCED SFC TO MID LEVEL THETA-E DIFFERENTIALS FOR SOME
LOCALIZED MICROBURSTS, PARTICULARLY IF CONVECTION CAN DEVELOP
DURING THE AFTERNOON TO EARLY EVENING HOURS. A SLIGHT RISK OF
SEVERE STORMS (LEVEL 2 OF 5) HAS BEEN MAINTAINED TODAY WITH
DAMAGING WIND GUSTS AND LOCALLY HEAVY RAIN STILL APPEARING AS
THE MAIN THREATS. GIVEN LOW SHEAR ENVIRONMENT, OUTFLOWS FROM
LATE AFTERNOON/EARLY EVENING CONVECTION MAY SUSTAIN SOME RENEWED
CONVECTIVE DEVELOPMENT THROUGH THE OVERNIGHT HOURS GIVEN SLOW
MOVING NATURE TO UPSTREAM SHORT WAVE.
SOME INDICATIONS FOR SATURDAY THAT SOME VERY SUBTLE MID LEVEL HEIGHT
RISES COULD DEVELOP FOR FIRST PART OF THE DAY IN WAKE OF THE SHORT
WAVE/MCV LATE TONIGHT. THIS DOES LEAD TO SOME LOW CONFIDENCE IN
CONVECTIVE EVOLUTION FOR SATURDAY. SHEAR PROFILES SHOULD BE
MARGINAL, WITH MODERATE AFTERNOON INSTABILITY STILL LIKELY. A
TRIGGER IS SOMEWHAT MURKY AT THIS FORECAST DISTANCE, WITH OLD
OUTFLOWS POSSIBLY PLAYING SOME ROLE ONCE AGAIN. THIS SETUP STILL
SUPPORTS A MARGINAL RISK (LEVEL 1 OF 5) FOR SATURDAY AFTERNOON/EARLY
EVENING WITH ONCE AGAIN AN ISOLATED WIND THREAT.
SOME CONSIDERATION WAS GIVEN TO EXTENDING HEAT HEADLINES INTO
SATURDAY FOR FAR SOUTH/SOUTHEAST AREAS, BUT COMPLICATIONS FROM
CONVECTIVE POTENTIAL AND DERIVED HEAT INDICES FROM FORECAST
GRIDS YIELDING PEAK AFTERNOON HEAT INDICES AROUND 100 ACROSS
THESE LOCATIONS ARGUE FOR MAINTAINING HEAT HEADLINES AS IS FOR
NOW.
PREDICTABILITY IN CONVECTIVE DETAILS DROPS OFF FURTHER FOR SUNDAY
AND MONDAY AS A PAIR OF SYNOPTIC WAVES WILL LIKELY UNDERGO SOME
CONVECTIVE MODIFICATION ONCE AGAIN, BUT OVERALL PATTERN AND TIMING
OF THIS FORCING WOULD SUPPORT ISOLATED-SCATTERED CONVECTION AGAIN ON
SUNDAY. INSTABILITY WILL LIKELY BE MORE LIMITED ON SUNDAY IN
COMPARISON TO TODAY AND SATURDAY, AND WITH PERSISTENCE OF MARGINAL
SHEAR PROFILES, AN ISOLATED SEVERE THREAT IS OF LOWER CONFIDENCE ON
SUNDAY.
SCATTERED POPS WERE MAINTAINED FOR MONDAY ALTHOUGH RECENT GUIDANCE
TRENDS COULD RESULT IN QUICKER TRANSITION TO DRY CONDITIONS AS
NEGATIVE HEIGHT ANOMALY BEGINS TO SHIFT OFF TO THE EAST.
TEMPS/HUMIDITY LEVELS SHOULD TRANSITION TO MORE SEASONABLE
LEVELS FOR EARLY NEXT WEEK. ADDITIONAL SHOWER AND STORM CHANCES
STILL LOOK GOOD LATER IN THE WEEK AS A SERIES OF PACIFIC WAVES
AND SLIGHTLY STRONGER NORTHERN TIER WESTERLIES SHIFTS INTO THE
GREAT LAKES REGION.
AVIATION /12Z TAFS THROUGH 12Z SATURDAY/
ISSUED AT 635 AM EDT FRI JUL 3 2026
SHOWERS AND STORMS THAT AFFECTED FAR NORTHERN INDIANA EARLIER
THIS MORNING HAVE DISSIPATED AS SOME WEAK LOW LEVEL CIN HAS
BECOME ESTABLISHED ACROSS NORTHERN INDIANA. CONVECTIVE FORECAST
TODAY WILL BE COMPLICATED BY REMNANT OUTFLOW BOUNDARIES FROM
LAST NIGHT'S CONVECTION AND ALSO TRYING TO RESOLVE
TIMING/STRENGTH OF UPSTREAM CONVECTIVELY ENHANCED SHORT WAVES
ALONG WITH ADDITIONAL OUTFLOWS FROM ONGOING CONVECTION ACROSS
THE PLAINS INTO THE CORN BELT. A HIGHLY UNSTABLE AIRMASS WILL BE
IN PLACE TODAY WITH CONTINUED INDICATIONS IN GUIDANCE OF
2500-3000 MLCAPES THIS AFTERNOON. WOULD SUSPECT SOME ISOLATED TO
SCATTERED SHOWER/STORM DEVELOPMENT IS POSSIBLE AFTER 19Z ALONG
REMNANT OUTFLOW BOUNDARIES, BUT MORE ORGANIZED CONVECTIVE THREAT
STILL APPEARS AS THOUGH IT WILL HOLD OFF UNTIL LATE
AFTERNOON/EVENING AS UPSTREAM SHORT WAVE BEGINS TO INTERACT WITH
THESE BOUNDARIES. GIVEN SOME QUESTION AS TO TIMING AND
COVERAGE, WILL CONTINUE WITH PROB30 MENTIONS WITH THE 12Z TAFS
AT BOTH TERMINALS UNTIL SOME OF THE MESOSCALE DETAILS CAN BE
BETTER RESOLVED TODAY. OUTFLOW INTERACTIONS COULD KEEP
CONVECTION GOING THROUGH 06Z, WITH LOWER CHANCES OF SHOWERS AND
STORMS DURING THE OVERNIGHT HOURS TONIGHT. OVERALL VFR
CONDITIONS ARE EXPECTED TO HOLD FOR MOST OF THIS PERIOD OUTSIDE
OF ANY STRONGER SHOWERS AND THUNDERSTORMS.
IWX WATCHES/WARNINGS/ADVISORIES
IN...HEAT ADVISORY UNTIL 8 PM EDT /7 PM CDT/ THIS EVENING FOR
INZ005>008-012>015-020-103-104-116-203-204-216.
EXTREME HEAT WARNING UNTIL 8 PM EDT THIS EVENING FOR INZ009-
017-018-022>027-032>034.
OH...EXTREME HEAT WARNING UNTIL 8 PM EDT THIS EVENING FOR OHZ001-
002-004-005-015-016-024-025.
MI...HEAT ADVISORY UNTIL 8 PM EDT THIS EVENING FOR MIZ078>081-177-
277.
MARINE...NONE.
DISCUSSION...MARSILI
AVIATION...MARSILI
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