616
FXUS63 KLOT 021743
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
1243 PM CDT THU JUL 2 2026
KEY MESSAGES
- HOT AND HUMID CONDITIONS WILL CONTINUE INTO THE HOLIDAY
WEEKEND, WITH PEAK HEAT INDEX VALUES AROUND 105 DEGREES TODAY
AND AROUND 100 DEGREES FRIDAY AND INDEPENDENCE DAY.
- WAVES OF THUNDERSTORMS ARE EXPECTED THROUGH THE WEEKEND. WITH
THAT SAID, THERE WILL BE MANY DRY HOURS. ANY THUNDERSTORMS ON
FRIDAY WILL BE CAPABLE OF PRODUCING DAMAGING WINDS.
DISCUSSION
ISSUED AT 300 AM CDT THU JUL 2 2026
HOT AND HUMID CONDITIONS WILL PERSIST TODAY, AND POSSIBLY OVER
SOME OR ALL OF THE FORECAST AREA ON FRIDAY. SLIGHT MIXING OF DEW
POINTS ACROSS A WEAKENING CAP TODAY SHOULD KEEP DEW POINTS IN
THE LOW TO POSSIBLY MID 70S. WITH TEMPS EXPECTED TO PEAK IN THE
LOW TO MID 90S, TODAY WILL FEATURE ANOTHER AFTERNOON WITH HEAT
INDEX VALUES IN THE 100 TO 105 DEGREE RANGE. MAINTAINED THE
CURRENT EXTREME HEAT WARNING THROUGH THIS EVENING, THOUGH SOME
CONSIDERATION OF AN EXTENSION THROUGH FRIDAY WILL BE NEEDED FOR
AT LEAST THE SOUTHERN HALF OF THE FORECAST AREA DEPENDING ON THE
EXPECTED OUTCOME OF CONVECTION TONIGHT INTO FRIDAY MORNING.
AS OF 3AM, ELEVATED CONVECTION CONTINUES TO DEVELOP ACROSS
CENTRAL WISCONSIN ALONG A GENERALLY WSW TO ENE CORRIDOR.
REMAINING CAPPING FARTHER SOUTH HAS RESULTED IN A NOTABLE
SOUTHERN TERMINUS OF THE CONVECTION FROM THE NORTHERN MILWAUKEE
METRO TO FAR NORTHEAST IOWA. A RESULTANT OUTFLOW HAS STARTED TO
SHOW SOME SLOWING WITH ITS SOUTHWARD TREK TOWARD THE STATE LINE,
BUT SHOULD SHIFT FAR ENOUGH SOUTH TO DISRUPT THE LOW-LEVEL WIND
FIELD FOR A FEW HOURS ACROSS THE NORTHERN TIER OF COUNTIES IN
NORTHERN ILLINOIS EARLY THIS MORNING. WITH RECENT CONVECTION
STRUGGLING TO EXTEND FARTHER SOUTH, CONCERNS FOR NEW CONVECTION
ALONG THIS OUTFLOW BOUNDARY ARE WANING WITH TIME. HOWEVER, HAVE
MAINTAINED A SLIGHT CHANCE OF SHOWERS AND STORMS OVER THESE
NORTHERN COUNTIES THROUGH MID-MORNING.
UNDER THE EXPECTATION THAT LITTLE TO NO CONVECTION OCCURS OVER
NORTHERN ILLINOIS THROUGH THE DAYTIME HOURS, THE FIRST FAVORED
WINDOW FOR STORMS WILL BE VERY LATE THIS EVENING INTO THE
OVERNIGHT HOURS. A MID-LEVEL WAVE EMANATING FROM EASTERN
COLORADO EARLY THIS MORNING AS EVIDENT BY WV IMAGERY AND
ASSOCIATED DOWNSTREAM CONVECTION MAY GO THROUGH A COUPLE
ITERATIONS OF CONVECTIVE ENHANCEMENT OVER THE NEXT 24 HOURS AS
IT TRACKS TOWARD CENTRAL WISCONSIN THROUGH THIS EVENING. IT
APPEARS LIKELY THAT A (POTENTIALLY) ORGANIZED CLUSTER OF
CONVECTION WILL DEVELOP SOMEWHERE AROUND THE NE/IA LINE BY EARLY
EVENING AND FOCUS ALONG A RESIDUAL OUTFLOW FROM CURRENT
CONVECTION. WITH THE ONGOING DE-AMPLIFICATION OF THE MID-LEVEL
RIDGE AND SUBSTANTIALLY LESS CAPPING OVER THE AREA BY THIS
EVENING, ANY WELL FORMED MCS COULD SURVIVE INTO SOUTHERN
WISCONSIN AND NORTHERN ILLINOIS LATE THIS EVENING INTO THE
OVERNIGHT HOURS. HOWEVER, CONVECTION WOULD LIKELY BECOME COLD
POOL DOMINANT WITH SOUTHWARD EXTENT AS STRONGER SHEAR/MID-LEVEL
FLOW REMAIN FARTHER NORTH OVER WISCONSIN. WITH THAT SAID, A
STRONGER COLD POOL SURGING INTO THE ANTECEDENT WARM AND HUMID
AIRMASS IMPLIES A POTENTIAL FOR STRONG TO LOCALLY DAMAGING WINDS
INTO PORTIONS OF NORTHERN ILLINOIS.
A MORE POTENT WAVE CURRENTLY CROSSING NORTHERN ARIZONA WILL
BECOME ANOTHER FOCUS FOR CONVECTION OVER OUR AREA ON FRIDAY.
THIS WAVE WILL CROSS SOUTHERN WISCONSIN MID TO LATE AFTERNOON,
SETTING THE STAGE FOR A POTENTIAL LINE OF CONVECTION IN THE AREA
LATER FRIDAY AFTERNOON INTO THE EVENING. IF CONVECTION
MATERIALIZES TONIGHT, THERE WILL LIKELY BE A NOTABLE OUTFLOW
BOUNDARY STALLED OVER THE FORECAST AREA FRIDAY MORNING THAT
COULD COMPLICATE THE FORECAST BY ALTERING THE LOCATION OF
CONVECTIVE INITIATION. MEANWHILE, NO CONVECTION TONIGHT WOULD
LEAD TO A FAIRLY UNTAPPED AND UNCAPPED AIRMASS OVER THE AREA
THROUGH THE ENTIRE DAY. WHILE THESE DIFFERENCES INTRODUCE A
DECENT AMOUNT OF UNCERTAINTY REGARDING THE TIMING AND LOCATION
OF CONVECTION, LATE AFTERNOON THROUGH MID-EVENING FRIDAY APPEAR
TO HAVE THE GREATEST CHANCE FOR AT LEAST A BROKEN LINE OF
STORMS OVER NORTHERN ILLINOIS AND NORTHERN INDIANA. MODEST DEEP
LAYER SHEAR AND AN INHERENT HIGH DCAPE RESERVOIR WITH THE
WARM/HUMID AIRMASS SUPPORT THE RISK FOR DAMAGING WINDS WITH ANY
LINEAR SEGMENT OR MULTICELL CLUSTERS.
A MID-LEVEL IMPULSE EXITING THE NORTHERN ROCKIES LATE ON FRIDAY
WILL PROVIDE RENEWED CONVECTIVE EPISODES IN THE REGION AS THE
MID-LEVEL PATTERN BECOMES ZONAL. THE TRACK OF THIS CONVECTION
WILL LIKELY FOCUS ALONG AN EFFECTIVE COLD FRONT PRODUCED BY THE
COMBINED EFFECTS OF CONVECTION OVER THE NEXT 48 HOURS. SO WHILE
CONVECTION SEEMS LIKELY IN THE REGION ON SATURDAY/INDEPENDENCE
DAY, THE LOCATION OF CONVECTION COULD RANGE FROM SOUTHERN
WISCONSIN TO SOUTHERN ILLINOIS. FURTHERMORE, WITH FORECAST
GUIDANCE CONSISTENTLY DEPICTING A SLOWING OR STALLING MID-LEVEL
WAVE OVER THE WESTERN GREAT LAKES LATE SATURDAY INTO EARLY NEXT
WEEK, TIMING OUT PRECIP CHANCES BECOMES EVEN MORE DIFFICULT IF
NOT IMPOSSIBLE.
AS THE AFOREMENTIONED WAVE EVENTUALLY DRIFTS EASTWARD, DRIER
AND SOMEWHAT COOLER CONDITIONS ARE EXPECTED BY THE MIDDLE OF
NEXT WEEK.
KLUBER
AVIATION /18Z TAFS THROUGH 00Z SATURDAY/
ISSUED AT 1243 PM CDT THU JUL 2 2026
KEY MESSAGES FOR THE 18Z TAF PERIOD:
* SCATTERED SHOWERS AND THUNDERSTORMS POSSIBLE OVERNIGHT INTO
VERY EARLY FRIDAY.
* ADDITIONAL THUNDERSTORMS DURING THE DAY ON FRIDAY, MOST LIKELY
DURING THE AFTERNOON.
A SYSTEM OF SHOWERS AND THUNDERSTORMS LOOKS TO MOVE ACROSS
NORTHERN IL LATE THIS EVENING INTO EARLY FRIDAY. STORMS MAY
APPROACH RFD AS EARLY AS LATE EVENING AND ARE MOST LIKELY AFTER
MIDNIGHT ACROSS CHICAGOLAND. GUSTY WINDS AND VSBY REDUCTIONS MAY
ACCOMPANY THE STORMS. THEY LOOK TO MOVE OUT NEAR OR JUST PRIOR
TO DAWN.
ADDITIONAL SHOWERS AND THUNDERSTORMS ARE ANTICIPATED AROUND THE
AREA ON FRIDAY. WHILE SOME MORNING PRECIP CANNOT BE RULED OUT,
CHANCES ARE GENERALLY HIGHEST DURING THE AFTERNOON AND EARLY
EVENING, ESPECIALLY INTO CHICAGOLAND, BUT EXACT TIMING OF ANY
STORMS IS UNCERTAIN. THUNDERSTORMS MAY BE ON THE STRONGER SIDE
FRIDAY AFTERNOON AND COULD FEATURE HEAVY DOWNPOURS AND STRONG
WIND GUSTS.
MEANWHILE, WINDS ARE VARIABLE IN BOTH DIRECTION AND MAGNITUDE
EARLY THIS AFTERNOON WITH A SERIES OF BOUNDARIES DISRUPTING THE
LOW LEVEL WIND FIELD. AS WE MOVE TOWARD MID-AFTERNOON, WINDS ARE
EXPECTED TO CONVERGE TOWARD SW AND MAY FEATURE SOME 20+ KT
GUSTS. DIRECTION MAY GO VARIABLE IN THE VICINITY OF STORMS BOTH
TONIGHT AND FRIDAY, BUT EXPECT LARGELY W WINDS DURING THE DAY ON
FRIDAY.
DOOM
CLIMATE
ISSUED AT 300 AM CDT THU JUL 2 2026
.DAILY RECORDS FOR THE WEEK........
CHICAGO (KORD)
RECORD HIGH RECORD WARM MINIMUM
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
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 TONIGHT 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/ TONIGHT FOR
INZ001-INZ002-INZ010-INZ011-INZ019.
LM...NONE.
VISIT US AT WEATHER.GOV/CHICAGO
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page