428
FXUS63 KIWX 020726
AFDIWX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE NORTHERN INDIANA
326 AM EDT THU JUL 2 2026
KEY MESSAGES
- THE EXTREME HEAT WARNING REMAINS IN EFFECT AREA-WIDE THROUGH THIS
EVENING. HIGHS IN THE LOW TO MID 90S AND HEAT INDICES BETWEEN
100 TO 110 DEGREES ARE EXPECTED THIS AFTERNOON.
- HEAT INDICES MAY EXCEED 100 DEGREES AGAIN ON FRIDAY, BUT HEAT
INDICES WILL BE DEPENDENT ON EXTENT OF AFTERNOON CLOUDS AND
ANY SCATTERED SHOWERS AND STORMS. ADDITIONAL HEAT HEADLINES
MAY BE NEEDED FOR FRIDAY.
- THERE IS A SLIGHT RISK OF SEVERE STORMS FRIDAY NORTH OF US
ROUTE 24, AND A MARGINAL RISK OF SEVERE STORMS FRIDAY SOUTH
OF US ROUTE 24. ISOLATED TO SCATTERED DAMAGING WIND GUSTS
APPEARS TO BE THE PRIMARY THREAT, BUT ISOLATED LARGE HAIL
CANNOT BE RULED OUT. ISOLATED STRONG TO SEVERE STORMS ARE ALSO
POSSIBLE DURING THE AFTERNOON AND EVENING HOURS FOR SATURDAY
AND SUNDAY.
- HOT AND HUMID CONDITIONS PERSIST FOR THE 4TH OF JULY, BUT HEAT
INDICES WILL BE HIGHLY DEPENDENT ON CLOUD COVERAGE AND
COVERAGE OF SHOWERS AND STORMS.
DISCUSSION
ISSUED AT 320 AM EDT THU JUL 2 2026
FOR ONGOING HEADLINES, THE EXTREME HEAT WARNING WILL BE MAINTAINED
AREA-WIDE THROUGH THIS EVENING. AS WILL BE DISCUSSED BELOW, HEAT
HEADLINES IN SOME FORM WILL LIKELY NEED TO BE EXTENDED INTO
FRIDAY, BUT CONVECTIVE POTENTIAL CONTINUES TO PROVIDE SOME
CHALLENGES TO HEAT FORECAST FOR FRIDAY.
A COMPLEX OF SHOWERS AND THUNDERSTORMS IS ONGOING EARLY THIS MORNING
FROM SOUTHEAST MINNESOTA INTO NORTHERN LOWER MICHIGAN. THESE
THUNDERSTORMS ARE OCCURING ALONG NORTHERN PERIPHERY OF MID LEVEL
RIDGING THAT HAS MAINTAINED DRY CONDITIONS LOCALLY OVER THE PAST
SEVERAL DAYS. AN OUTFLOW BOUNDARY EMANATING FROM THIS CONVECTION IS
CURRENTLY APPROACHING SOUTHEAST WISCONSIN AS OF 07Z THIS
MORNING. THIS BOUNDARY IS EXPECTED TO SLOW ITS SOUTHEAST
PROGRESS AND BECOME MORE SHALLOW IN NATURE AS IT LIKELY STALLS
ACROSS THE SOUTHERN GREAT LAKES REGION THIS MORNING. THERE IS A
NON-ZERO CHANCE FOR AN ISOLATED SHOWER OR STORM TO DEVELOP ALONG
THIS RESIDUAL BOUNDARY THIS MORNING ACROSS FAR NW IN TO S LOWER
MI, BUT WOULD SUSPECT AS THIS BOUNDARY BECOMES MORE DIVORCED
FROM STRONGER MID/UPPER LEVEL FORCING, ADDITIONAL CONVECTION
WILL BE HARD TO COME BY GIVEN CONVERGENCE FIELDS BECOMING LESS
DEFINED THROUGH TIME. THUS, WILL MAINTAIN SOME SILENT 10 POPS
ACROSS THE FAR NORTH/NORTHWEST THIS MORNING. IT IS POSSIBLE THE
SOUTHERN PERIPHERY OF CONVECTIVELY ENHANCED VORT MAX COULD
TRACK ACROSS SE LOWER MICHIGAN THIS AFTERNOON WHICH COULD HELP
INITIATE AN ISOLATED SHOWER OR THUNDERSTORM ALONG THE RESIDUAL
OUTFLOW BOUNDARY NORTH OF US 6. HOWEVER, ONCE AGAIN, CONFIDENCE
IN THIS SCENARIO IS QUITE LOW GIVEN POTENTIAL OF SOME WEAK
SURFACED BASED CIN LIKELY TO PERSIST.
OTHERWISE FOR TODAY, PERSISTENCE FORECAST MAINTAINED FOR
TEMPERATURE/HEAT INDEX FORECAST ALTHOUGH SOME SLIGHT MODERATION OF
LOW LEVEL TEMPERATURES IS POSSIBLE TODAY AS THE MID/UPPER LEVEL
RIDGE GETS SLIGHTLY SUPPRESSED BY THE CONVECTIVELY ENHANCED SHORT
WAVE TRACKING ACROSS THE SOUTHERN GREAT LAKES. IF TEMPS ARE SLIGHTLY
COOLER TODAY, THIS COULD BE OFFSET BY DEW POINTS WHICH COULD BE
SLIGHTLY HIGHER IN SPOTS TODAY IN COMPARISON TO YESTERDAY. THIS
SHOULD PRODUCE ANOTHER DAY OF PEAK AFTERNOON HEAT INDICES FROM
100 TO 110 AND THE EXTREME HEAT WARNING WILL BE MAINTAINED
THROUGH THIS EVENING.
FOR TONIGHT, WILL NEED TO WATCH FOR THE POSSIBILITY OF ANOTHER
CONVECTIVELY ENHANCED SHORT WAVE TO IMPACT THE REGION. THIS
POTENTIAL WILL BE HIGHER IN COMPARISON TO THIS MORNING AS THE
MID/UPPER RIDGE CONTINUES TO SLOWLY GET SUPPRESSED PROVIDING A
MORE FAVORABLE TRACK INTO THE LOCAL AREA. THE SOURCE REGION OF
THIS NEXT SHORT WAVE WILL LIKELY EMANATE FROM ONGOING CONVECTION
THIS MORNING DOWNSTREAM OF A CENTRAL PLAINS SHORT WAVE. SOME
HIGHER LOW LEVEL THETA-E AIR WILL ALSO CONTINUE TO WRAP
ANTICYCLONICALLY INTO THE REGION TONIGHT AS THE HEIGHT MAXIMUM
WITH THE UPPER LEVEL RIDGE BEGINS TO SHIFT INTO THE MID ATLANTIC
STATES BY DAYBREAK FRIDAY. THE FAR NORTH REMAINS IN SWODY2
MARGINAL RISK, WHICH WOULD LIKELY BE IN ASSOCIATION WITH AN
ISOLATED LATE WIND RISK TONIGHT. SOMEWHAT UNFAVORABLE DIURNAL
TIMING AND UNCERTAINTY IN STRENGTH OF THIS VORT MAX LEADS TO LOW
CONFIDENCE IN ANY ISOLATED SEVERE RISK TONIGHT ACROSS THE
NORTH. CONFIDENCE IS A LITTLE HIGHER THAT SOME TYPE OF LOOSELY
ORGANIZED SPS LEVEL COMPLEX OF SHOWERS AND STORMS COULD WORK
ACROSS THE REGION LATE.
FRIDAY WILL FEATURE BOTH CONVECTIVE AND POTENTIAL HEAT CONCERNS ONCE
AGAIN. SEVERAL ADDITIONAL PROGRESSIVE SHORT WAVES ARE PROGGED TO
SHIFT EAST OUT OF THE NORTHERN ROCKIES INTO THE CORN BELT REGION FOR
FRIDAY. THE WEAK CIN WHICH MAY BE PRESENT TODAY SHOULD BE ERODED
BY FRIDAY DUE TO SUPPRESSION OF MID/UPPER LEVEL RIDGE AND
CONCERN WILL BE FOR AFTERNOON/EVENING HOURS FOR SCATTERED
THUNDERSTORM DEVELOPMENT DOWNSTREAM OF YET ANOTHER LIKELY
CONVECTIVELY AIDED VORT MAX. MUCH OF THE NORTH OF US ROUTE 24
PORTION OF CWA HAS BEEN INCLUDED IN A SLIGHT RISK OF SEVERE
STORMS FOR FRIDAY, WITH A MARGINAL RISK OF SEVERE STORMS
ELSEWHERE. EARLIER INDICATIONS MAY SUGGEST AREAS NORTH OF US-6
WITH THE GREATEST POTENTIAL OF STRONG/SEVERE STORMS WHICH COULD
REPRESENT BEST OVERLAY OF INSTABILITY AND SLIGHTLY BETTER SHEAR
PROFILES ACROSS THE SOUTHERN GREAT LAKES. STEEP 0-3KM LAPSE
RATES AND POTENTIAL PRECIP-LOADING/UNIDIRECTIONAL WIND PROFILES
SUGGEST DAMAGING WIND GUSTS WOULD BE THE GREATEST POTENTIAL
THREAT FRIDAY AFTERNOON/EVENING.
A CHALLENGE FOR FRIDAY WILL BE HOW TEMP/HEAT INDEX FORECAST IS
IMPACTED BY THE CONVECTIVE POTENTIAL. SOME THOUGHT WAS GIVEN THIS
MORNING OF EXTENDING THE EXTREME HEAT WARNING THROUGH FRIDAY. UPON
COLLABORATION WITH SURROUNDING OFFICES, HAVE OPTED TO HOLD OFF AT
THIS TIME GIVEN CONVECTIVE UNCERTAINTIES, PARTICULARLY IF ANY
ORGANIZED OUTFLOW BOUNDARY CAN PUSH THROUGH FRIDAY AM. THE SOUTHEAST
THIRD OF THE AREA APPEARS AT THIS FORECAST DISTANCE TO HAVE BEST
CHANCE OF AN ADDITIONAL DAY OF 100+ HEAT INDICES. AS MENTIONED IN
PREVIOUS DISCUSSION THIS COULD VERY WELL BE A CASE WHERE WARNINGS
ARE EXTENDED INTO FRIDAY ACROSS THE SOUTHEAST, WITH ADVISORY
SCENARIO ELSEWHERE.
ON SATURDAY, A SOMEWHAT MORE PRONOUNCED SYNOPTIC WAVE COULD EJECT
OUT OF WESTERN CONUS LONGWAVE TROUGH AND WILL SLOWLY TRACK ACROSS
MID/UPPER MS VALLEY AND WESTERN GREAT LAKES THROUGH SUNDAY,
EVENTUALLY TAKING A COOL FRONT SOUTH THROUGH THE AREA. SOME ISOLATED
SEVERE POTENTIAL IS POSSIBLE THIS WEEKEND, BUT CONFIDENCE IN DETAILS
VERY LOW AT THIS POINT GIVEN LOW PREDICTABILITY WITH CONVECTIVE
ENHANCEMENT OF THESE SHORT WAVES.
PRECIP CHANCES SHOULD LESSEN EARLY NEXT WEEK AS BROAD LOW LEVEL
ANTICYCLONE SETTLES ACROSS THE GREAT LAKES. MEDIUM RANGE GUIDANCES
DOES SUGGEST SOME UPTICK IN NORTHERN TIER WESTERLIES MIDDLE TO LATE
NEXT WORK WEEK WITH WARMING CONDITIONS AND ADDITIONAL CONVECTIVE
CHANCES AS ADDITIONAL SHORT WAVE PROGRESS THROUGH NORTHERN TIER
FLOW.
AVIATION /06Z TAFS THROUGH 06Z FRIDAY/
ISSUED AT 140 AM EDT THU JUL 2 2026
WIDESPREAD SHOWERS AND STORMS CONTINUE EARLY THIS MORNING ALONG
AN AXIS FROM SOUTHEAST MINNESOTA TO THE NORTHERN LAKE MICHIGAN
VICINITY. MID LEVEL RIDGING ACROSS THE OHIO VALLEY SHOULD HOLD
ENOUGH STRENGTH THIS MORNING TO KEEP FOCUS FOR SHOWERS AND
STORMS WELL NORTHWEST OF THE TERMINALS. HOWEVER, MAY NEED TO
WATCH PROGRESS OF SOUTHEAST PROGRESSING OUTFLOW BOUNDARY FROM
THIS CONVECTION, AND IF CAN REACH AS FAR SOUTH AS THE SOUTHERN
GREAT LAKES. THIS OUTFLOW COULD KICK OFF AN ISOLATED SHOWER OR
STORM DURING THE DAY TODAY, BUT CONFIDENCE IN OCCURRENCE AND
LIMITED COVERAGE STILL SUGGESTS OMITTING MENTION FROM TAFS IS
BEST COURSE OF ACTION AT THIS TIME. CHANCES OF SHOWERS AND
STORMS MAY TEND TO INCREASE LATE IN THIS FORECAST VALID PERIOD
THIS EVENING AS MID LEVEL RIDGE BECOMES SLIGHTLY MORE SUPPRESSED
AND AS ANOTHER CONVECTIVELY ENHANCED IMPULSE TOPS THE RIDGE
ACROSS THE CORN BELT. OTHERWISE, CANNOT COMPLETELY RULE OUT SOME
BRIEF MVFR VSBYS IN LIGHT SHALLOW FOG EARLY THIS MORNING, BUT
VFR CONDITIONS SHOULD HOLD THROUGH THE PERIOD. IN SIMILAR
FASHION TO YESTERDAY, PEAK MIXING THIS AFTERNOON SHOULD YIELD
SOUTHWEST WINDS AROUND 20 KNOTS AT KSBN WHERE GRADIENT SHOULD BE
A BIT MORE PRONOUNCED.
IWX WATCHES/WARNINGS/ADVISORIES
IN...EXTREME HEAT WARNING UNTIL 8 PM EDT /7 PM CDT/ THIS EVENING
FOR INZ005>009-012>015-017-018-020-022>027-032>034-103-
104-116-203-204-216.
OH...EXTREME HEAT WARNING UNTIL 8 PM EDT THIS EVENING FOR OHZ001-
002-004-005-015-016-024-025.
MI...EXTREME HEAT WARNING UNTIL 8 PM EDT THIS EVENING FOR
MIZ078>081-177-277.
MARINE...NONE.
DISCUSSION...MARSILI
AVIATION...MARSILI
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