199
FXUS63 KLOT 292330
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
630 PM CDT MON JUN 29 2026
KEY MESSAGES
- DANGEROUS HEAT WAVE WILL CONTINUE THROUGH AT LEAST WEDNESDAY
WITH DAYTIMES HIGHS IN THE 90S AND PEAK AFTERNOON HEAT INDICES
OF 100 TO 110 DEGREES.
- DANGEROUS HEAT MAY CONTINUE INTO THURSDAY, THOUGH FORECAST
CONFIDENCE IS LOWER DUE TO THE POTENTIAL EFFECTS FROM STORMS.
- THUNDERSTORM CHANCES WILL BEGIN TO INCREASE LATE IN THE WEEK,
LIKELY BRINGING SOME HEAT RELIEF FOR AT LEAST SOME AREAS.
- WHILE LIKELY NOT A COMPLETE WASH OUT, THERE WILL BE PERIODIC
CHANCES FOR THUNDERSTORM THROUGH THE HOLIDAY WEEKEND.
DISCUSSION
ISSUED AT 1253 PM CDT MON JUN 29 2026
A STRONG UPPER RIDGE OVER THE OHIO VALLEY WILL MOVE VERY LITTLE
THROUGH WEDNESDAY SETTING THE STAGE FOR A CONTINUATION OF THE
HEAT AND HUMIDITY. MOST GUIDANCE DEPICTS 925MB TEMPS WARMING
ANOTHER 1-2C TUESDAY, SO HIGH TEMPS WILL LIKELY BE A COUPLE/FEW
DEGREES HOTTER THAN TODAY. A STRONG LOW LEVEL INVERSION HAS
LIMITED THE DEPTH OF MIXING TODAY AND FORECAST SOUNDINGS SUGGEST
A SIMILARLY STRONG INVERSION TUESDAY. THIS STRONG INVERSION
LIMITING MIXING PLUS THE BEGINNINGS OF EVAPOTRANSPIRATION (ET)
SEASON HAS RESULTED IN DEWPOINTS HIGHER THAN PRETTY MUCH ALL
AVAILABLE GUIDANCE TODAY. WE ARE ABOUT A WEEK AWAY FROM REACHING
50% PEAK FROM CORN, SO WHILE IT IS STILL EARLY, IT LIKELY IS
STILL A CONTRIBUTING FACTOR. GIVEN THIS, I CONTINUED TO TREND
DEWPOINTS TOWARD THE HIGH END OF THE GUIDANCE SPECTRUM TUESDAY,
WHICH COULD PUSH HEAT INDICES LOCALLY TO AROUND 110F DEGREES IN
THE AFTERNOON.
BY WEDNESDAY, THERE ARE SIGNALS IN THE MODELS THAT DEEPER MIXING
COULD RESULT IN SOMEWHAT LOWER DEWPOINTS, BUT HIGHER AIR TEMPS.
THE NET RESULT MAY BE HEAT INDICES A COUPLE/FEW DEGREES LOWER
THAN TUESDAY, BUT WITH AIR TEMPS POTENTIALLY REACHING INTO THE
UPPER 90S ANY SLIGHT IMPROVEMENT IN HEAT INDICES WILL BE MORE
ACADEMIC. IF GUIDANCE ENDS UP BEING TOO AGGRESSIVE IN MIXING OUT
DEWPOINTS WEDNESDAY, THEN ANOTHER DAY WITH HEAT INDICES OF 105
TO 110F WOULD OCCUR.
THE HEART OF THE UPPER RIDGE IS EXPECTED TO DRIFT EASTWARD SOME
WEDNESDAY NIGHT INTO THURSDAY WHICH WOULD PLACE OUR AREA
PRECARIOUSLY CLOSE TO THE PROVERBIAL "RING OF FIRE" CONVECTION.
MOST AVAILABLE GUIDANCE KEEPS CONVECTION NORTH OF THE AREA
THROUGH MUCH OF THE DAY THURSDAY, WHICH WOULD RESULT IN A 4TH
CONSECUTIVE DAY OF HEAT INDICES OF 100-110F. THIS WOULD TRIGGER
AN EXTREME HEAT WARNING AREA-WIDE, SINCE THE WARNING CRITERIA
INCLUDES 4 CONSECUTIVE DAYS OF ADVISORY LEVEL HEAT INDICES.
PONDERED THE UPGRADE/EXTENSION INTO THURSDAY, BUT OPTED TO HOLD
OFF FOR NOW GIVEN SOME LINGERING UNCERTAINTIES WITH RESPECT TO
POTENTIAL CONVECTION, CONVECTIVE DEBRIS CLOUDINESS, AND/OR
OUTFLOW POTENTIALLY DISRUPTING THE HEAT THURSDAY. GUIDANCE IS
VERY OFTEN TOO FAR NORTH WITH CONVECTION/CONVECTIVE EFFECTS IN
THESE TYPE OF SET-UPS, SO WHILE THE SIGNAL IS PRETTY STRONG FOR
ANOTHER DAY OF DANGEROUS HEAT THURSDAY, STILL THINK IT IS
POSSIBLE THAT AT LEAST PART OF THE AREA COULD SEE SOME RELIEF
THURSDAY DUE TO CONVECTION AND/OR CONVECTIVE EFFECTS.
A MORE ACTIVE PATTERN IS EXPECTED THURSDAY NIGHT THROUGH THE
UPCOMING HOLIDAY WITH AT LEAST PERIODIC CHANCES FOR SHOWERS AND
THUNDERSTORMS. THERE WILL LIKELY BE MANY DRY HOURS, BUT AN MCS
OR TWO WILL LIKELY TRAVERSE THE REGION AT SOME POINT THIS
WEEKEND.
- IZZI
AVIATION /00Z TAFS THROUGH 06Z WEDNESDAY/
ISSUED AT 630 PM CDT MON JUN 29 2026
VFR CONDITIONS ARE FORECAST THROUGH THE PERIOD. GUSTY SSW WINDS
THIS EVENING WILL EASE WITH SUNSET BUT MAY REMAIN AT LEAST
SPORADICALLY GUSTY THROUGH THE NIGHT. WINDS THEN PICK BACK UP
DURING THE DAY ON TUESDAY, PARTICULARLY IN THE AFTERNOON, WITH
GUSTS BACK INTO THE MID 20 KT RANGE OUT OF THE SW. WINDS THEN
EASE AGAIN AFTER SUNSET.
PETR
CLIMATE
ISSUED AT 252 AM CDT SUN JUN 28 2026
.DAILY RECORDS FOR THE UPCOMING WEEK........
CHICAGO (KORD)
RECORD HIGH RECORD WARM MINIMUM
JUNE 29 97 (1954) 80 (1931)
JUNE 30 99 (1953) 80 (2018)
JULY 1 103 (1956) 78 (1931)
JULY 2 99 (1970) 79 (1911)
JULY 3 102 (1949) 78 (1911)
JULY 4 102 (2012) 80 (1921)
ROCKFORD (KRFD)
RECORD HIGH RECORD WARM MINIMUM
JUNE 29 103 (1931) 75 (1931)
JUNE 30 102 (1931) 76 (2018)
JULY 1 101 (1931) 76 (1970)
JULY 2 99 (1910) 74 (1970)
JULY 3 99 (1925) 75 (2012)
JULY 4 102 (2012) 77 (1977)
NWS CHICAGO
LOT WATCHES/WARNINGS/ADVISORIES
IL...HEAT ADVISORY UNTIL 10 PM CDT WEDNESDAY FOR ILZ003-ILZ004-
ILZ005-ILZ006-ILZ008-ILZ010-ILZ011-ILZ012-ILZ013-ILZ019-
ILZ020-ILZ021-ILZ023-ILZ032-ILZ033-ILZ039-ILZ106-ILZ107-
ILZ108.
EXTREME HEAT WARNING UNTIL 10 PM CDT WEDNESDAY FOR ILZ103-
ILZ104-ILZ105.
IN...HEAT ADVISORY UNTIL 10 PM CDT /11 PM EDT/ WEDNESDAY FOR INZ001-
INZ002-INZ010-INZ011-INZ019.
LM...SMALL CRAFT ADVISORY UNTIL 10 PM CDT THIS EVENING FOR THE IL
NEARSHORE WATERS.
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