289
FXUS63 KIWX 030804
AFDIWX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
404 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 /06Z TAFS THROUGH 06Z SATURDAY/
ISSUED AT 155 AM EDT FRI JUL 3 2026
CONVECTIVE POTENTIAL WILL CONTINUE TO BE THE PRIMARY AVIATION
WEATHER CONCERN. A CLUSTER OF SHOWERS AND THUNDERSTORMS ACROSS
NORTHEAST ILLINOIS INTO SOUTHWEST LOWER MICHIGAN HAS KICKED AN
OUTFLOW BOUNDARY SOUTHWARD THAT HAS JUST PASSED THROUGH KSBN
VICINITY. SHOWERS AND A FEW STORMS HAVE ATTEMPTED TO DEVELOP
ALONG THIS OUTFLOW BOUNDARY, BUT DEVELOPMENT OF SOME WEAK MLCIN
OVERNIGHT MAY TEND TO LIMIT COVERAGE AND RESULT IN SOME
DIMINISHMENT OF UPSTREAM CONVECTION AS IT PUSHES EAST. WITH
CONTINUED LOW CONFIDENCE IN NEAR TERM, HAVE INDICATED A PROB30
THUNDER MENTION AT KSBN WITH A POTENTIAL OUTFLOW BOUNDARY COULD
BE A FOCAL POINT, AND THE POSSIBILITY THAT CONVECTIVE COMPLEX
ACROSS NORTHEAST ILLINOIS SURVIVES EASTWARD. A MORE ORGANIZED
ROUND OF CONVECTION IS STILL EXPECTED LATE THIS AFTERNOON INTO
THIS EVENING AS ANOTHER CONVECTIVELY ENHANCED SHORT WAVE FROM
THE PLAINS ROUNDS THE FLATTENING UPPER RIDGE AND INTERACTS WITH
AN UNSTABLE AIRMASS. SOME UNCERTAINTIES PERSIST REGARDING WHERE
LEFTOVER OUTFLOW BOUNDARIES FROM THIS MORNING'S CONVECTION WILL
BE LOCATED AND ALSO TIMING THE CONVECTIVELY ENHANCED SHORT WAVE.
COULD SEE ISOLATED-SCATTERED STORMS DEVELOP TOWARD 19-20Z ALONG
REMNANT OUTFLOW BOUNDARY THAT MAY BEGIN TO SLOWLY RETREAT
NORTHWARD ACROSS FAR NORTHERN INDIANA. BETTER CHANCE OF STORMS
STILL LOOKS TO BE IN THE 22Z-03Z TIMEFRAME AS THE SHORT WAVE
APPROACHES. GIVEN THE UNCERTAINTIES MENTIONED, WILL LIMIT
AFTERNOON/EVENING CONVECTION AT TERMINALS TO A PROB30 FOR NOW.
OUTSIDE OF ANY HEAVIER SHOWERS AND STORMS, VFR CONDITIONS SHOULD
HOLD THROUGH THIS PERIOD.
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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