287
FXUS63 KLOT 010049 CCA
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
616 PM CDT TUE JUN 30 2026
KEY MESSAGES
- DANGEROUS HEAT WAVE CONTINUES INTO THURSDAY, WITH DAYTIMES
HIGHS IN THE LOW TO MID 90S AND PEAK AFTERNOON HEAT INDICES OF
100 TO 105 DEGREES (LOCALLY HIGHER).
- WHILE NOT A COMPLETE WASH OUT, THUNDERSTORM CHANCES INCREASE
LATE THURSDAY, WITH A COUPLE OF WAVES OF SHOWERS AND
THUNDERSTORMS EXPECTED FRIDAY INTO THE 4TH OF JULY WEEKEND.
SOME STORMS MAY BE SEVERE AND PRODUCE HEAVY RAINFALL.
DISCUSSION
ISSUED AT 208 PM CDT TUE JUN 30 2026
THE ONGOING HEAT AND HUMIDITY CONTINUES TO BE THE PRIMARY WEATHER
STORY THROUGH THURSDAY.
A PERSISTENT UPPER-LEVEL RIDGE, WITH H5 HEIGHTS IN EXCESS OF
596 DAM, WILL REMAIN CENTERED ACROSS KENTUCKY AND TENNESSEE
THROUGH WEDNESDAY, BEFORE GRADUALLY EXPANDING EASTWARD TOWARDS
THE CENTRAL ATLANTIC COAST FOR THE SECOND HALF OF THE WEEK.
STRONG CAPPING UNDER THIS RIDGE WILL CONTINUE CURTAIL THE THREAT
FOR SHOWERS AND THUNDERSTORMS LOCALLY THROUGH AT LEAST THURSDAY
AFTERNOON/EVENING. ACCORDINGLY, UNABATED DIURNAL HEATING OF THE
VERY MOIST LOW-LEVEL AIRMASS WILL PUSH AFTERNOON HIGH
TEMPERATURES IN THE LOW TO MID 90S (HIGHEST IN THE URBAN AREAS
AROUND CHICAGO) EACH AFTERNOON THROUGH AT LEAST THURSDAY. WHEN
COMBINED WITH SURFACE DEWPOINTS IN THE LOW TO MID 70S, HEAT
INDICES WILL AGAIN TOP OUT IN THE 100-105 DEGREE RANGE (LOCALLY
IN EXCESS OF 105) BOTH WEDNESDAY AND THURSDAY. MEANWHILE, EXPECT
VERY WARM OVERNIGHT TEMPERATURES, WITH READINGS LIKELY
STRUGGLING TO FALL OUT OF THE LOW 80S IN THE CITY TONIGHT AND
AGAIN WEDNESDAY NIGHT. WHILE SUCH READINGS ARE NOT NECESSARILY
UNCOMMON TO EXPERIENCE ON A DAY IN THE MIDDLE OF SUMMER IN OUR
AREA, IT IS LESS COMMON TO EXPERIENCE SUCH CONDITIONS ON 4+
STRAIGHT DAYS WITH LITTLE TO NO RELIEF. IT IS THUS THE
CUMULATIVE EFFECTS OF THE HEAT THAT IS MOST CONCERNING WITH THIS
HEAT, AND NOT NECESSARILY THE PEAK TEMPERATURES AND HEAT
INDICES ON AN INDIVIDUAL DAY. THEREFORE, NO CHANGES ARE PLANNED
TO GOING HEAT HEADLINES CURRENTLY IN EFFECT.
WEDNESDAY, AND MUCH OF THURSDAY, WAVES OF SEVERE THUNDERSTORMS
WILL CONTINUE TO BE FAVORED NORTHWEST OF OUR AREA (FROM THE
PLAINS NORTHEASTWARD THROUGH THE UPPER MIDWEST) WITHIN A BELT OF
ACTIVE WEST-SOUTHWESTERLY UPPER-LEVEL FLOW RESIDING ALONG THE
WEST-NORTHWESTERN PERIPHERY OF THE UPPER-RIDGE. HOWEVER, AS THE
UPPER RIDGE BEGINS TO EXPAND EASTWARD, IT WILL ALLOW THIS ACTIVE
BELT OF WESTERLY UPPER-LEVEL FLOW TO SHIFT INTO OUR AREA LATE
IN THE WEEK. ACCORDINGLY, WHILE OUR AREA WILL GET RELIEF FROM
THE EXTREME HEAT THIS WEEKEND, IT WILL COME AT THE PRICE OF
INCREASING CHANCES FOR SHOWERS AND THUNDERSTORMS. WHILE IT WILL
NOT BE RAINING AND STORMING CONSTANTLY, IT APPEARS WE MAY END UP
WITH A COUPLE OF WAVES OF SHOWERS AND THUNDERSTORMS DURING THE
HOLIDAY WEEKEND, MOST NOTABLY LATE FRIDAY AND ON SATURDAY. SOME
OF THESE STORMS COULD BE SEVERE AND PRODUCE TORRENTIAL
DOWNPOURS.
KJB
AVIATION /00Z TAFS THROUGH 06Z THURSDAY/
ISSUED AT 616 PM CDT TUE JUN 30 2026
FORECAST CONCERN FOR THE TERMINALS...
- BREEZY SOUTHWEST WINDS EARLY THIS EVENING THEN AGAIN WEDNESDAY
AFTERNOON WITH GUSTS AROUND 25-30 KTS.
A BROAD AREA OF HIGH PRESSURE CONTINUES TO RESIDE OVER THE EASTERN
CONUS WHICH WILL ALLOW MOSTLY CLEAR VFR SKIES AND HOT CONDITIONS TO
PREVAIL THROUGH THE TAF PERIOD. HOWEVER, THERE IS A NON-ZERO CHANCE
(10-15%) FOR A FEW MVFR CLOUDS (BASES AROUND 2000-2500 FT) TO
DEVELOP LATE TONIGHT INTO WEDNESDAY MORNING.
GIVEN THE LOW CONFIDENCE ON THE COVERAGE AND DURATION OF THESE
LOWER CLOUDS HAVE OPTED TO MAINTAIN THE SCT020 IN THE TAFS FOR
NOW.
OTHERWISE, THE MAIN FORECAST ITEM OF NOTE WILL BE THE BREEZY
SOUTHWEST WINDS GUSTING AROUND 25-30 KTS EARLY THIS EVENING AND
AGAIN WEDNESDAY AFTERNOON. WHILE GUSTS WILL EASE OVERNIGHT, SOME
OCCASIONAL 15-17 KT GUSTS WILL BE POSSIBLE AT TIMES TONIGHT AND
AGAIN WEDNESDAY NIGHT.
YACK
CLIMATE
ISSUED AT 1249 AM CDT TUE JUN 30 2026
.DAILY RECORDS FOR THE UPCOMING WEEK........
CHICAGO (KORD)
RECORD HIGH RECORD WARM MINIMUM
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 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...EXTREME HEAT WARNING UNTIL MIDNIGHT CDT THURSDAY NIGHT FOR
ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-ILZ010-ILZ011-ILZ012-
ILZ013-ILZ019-ILZ020-ILZ021-ILZ023-ILZ032-ILZ033-ILZ039-
ILZ103-ILZ104-ILZ105-ILZ106-ILZ107-ILZ108.
IN...EXTREME HEAT WARNING UNTIL MIDNIGHT CDT /1 AM EDT/ THURSDAY
NIGHT FOR INZ001-INZ002-INZ010-INZ011-INZ019.
LM...SMALL CRAFT ADVISORY UNTIL 9 PM CDT THIS EVENING FOR WINTHROP
HARBOR IL TO GARY IN.
VISIT US AT WEATHER.GOV/CHICAGO
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