261
FXUS63 KLOT 031943
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
243 PM CDT FRI JUL 3 2026
KEY MESSAGES
- AN ADDITIONAL ROUND OF STORMS IS EXPECTED THIS EVENING
STARTING AT 6 OR 7 PM, AND LASTING THROUGH THE OVERNIGHT
HOURS. CONFIDENCE ON WHERE THE NEXT ROUND OCCURS REMAINS LOW,
BUT MAY FAVOR THE I-80 OR PERHAPS EVEN I-88 CORRIDOR.
- ADDITIONAL ROUNDS OF STORMS MAY MOVE THROUGH THE AREA TOMORROW
AND SUNDAY.
DISCUSSION
ISSUED AT 243 PM CDT FRI JUL 3 2026
REST OF TODAY/TONIGHT:
ROUND ONE OF THUNDERSTORMS IS SURELY LIVING UP TO EXPECTATIONS
WITH NUMEROUS MEASURED SEVERE WIND GUSTS RANGING FROM 60 TO 73
MPH. WHILE THE MAIN PUSH OF STORMS IS NOW MOVING TOWARD LOWER
MICHIGAN, A FEW MORE CELLULAR STORMS CONTINUE TO PERCOLATE ALONG
THE REMNANT OUTFLOW BOUNDARY STRETCHING SOUTHWESTWARD FROM
JOLIET TO LACON TO MACOMB, ILLINOIS. NORTH OF THE OUTFLOW
BOUNDARY, IT FEELS THE MOST COMFORTABLE IT HAS IN THE PAST WEEK
WITH TEMPERATURES LARGELY IN THE LOW TO MID 70S. MEANWHILE,
SOUTH OF THE FRONT, IT'S HOT AND STICKY WITH HEAT INDEX VALUES
IN THE 100 TO 105F RANGE.
FOCUS IS ON THE POTENTIAL FOR A SECOND ROUND OF STORMS THIS
EVENING. WHILE SOUTHWESTERLY FLOW ON THE SOUTHERN SIDE OF THE
OUTFLOW BOUNDARY IS NOT PARTICULARLY STRONG (10 TO LOCALLY 15
KT), HAVE BEEN NOTING THE BEGINNING OF THE NORTHWARD RETREAT OF
THE UNSTABLE AIRMASS BACK TOWARD NORTHWESTERN ILLINOIS. JUST HOW
FAR NORTHWEST THE UNSTABLE AIRMASS RETREATS IS AN ITEM OF LOW
CONFIDENCE, BUT SUSPECT IT WILL BE ABLE TO REACH I-80 AND
PERHAPS EVEN I-88 BY THIS EVENING AHEAD OF AN UPPER-LEVEL
SHORTWAVE CURRENTLY MOVING THROUGH THE SOUTHERN IOWA REGION. AS
A RESULT, CONCERN REMAINS FOR ANOTHER ROUND OF STORMS NEAR THE
FRONTAL BOUNDARY (PERHAPS EXTENDING EASTWARD FROM ONGOING STORMS
NEAR KANSAS CITY, MO) AS THE WAVE MOVES APPROACHES OUR AREA.
TIMING THE SECOND ROUND STILL LOOKS TO START SOMETIME IN THE 6
TO 7 PM TIMEFRAME WITH SCATTERED STORMS CONTINUING THROUGH THE
OVERNIGHT HOURS.
WHILE THE WAVE OF STORMS THAT CAME THROUGH EARLIER TODAY WERE
ANCHORED BY A NOTABLE 500MB WIND MAX, FLOW THIS EVENING WILL BE
WEAKER AND MORE ON THE ORDER OF 25-30 KT. AS A RESULT, CURRENT
THINKING IS THAT COVERAGE OF SEVERE WEATHER THIS EVENING WILL
NOT BE AS HIGH AS IT WAS WITH THE FIRST ROUND OF STORMS.
NEVERTHELESS, MOISTURE-LADEN MUCAPE >3000 J/KG WILL STILL
SUPPORT WATER-LOADED MICROBURSTS WITH A THREAT FOR TORRENTIAL
DOWNPOURS AND LOCALIZED WIND DAMAGE. IN ADDITION, WITH STORMS
MORE LIKELY TO ADOPT A WEST-TO-EAST ORIENTATION THIS EVENING, DO
HAVE CONCERN FOR LOCALIZED FLASH FLOODING PARTICULARLY IF THE
FRONT DOES MAKE IT BACK TOWARD THE I-88 CORRIDOR WHERE 3 TO
LOCALLY 5 INCHES OF RAIN FELL LAST NIGHT. IF IT BECOMES CLEAR
SUCH A THREAT WILL MATERIALIZE, WILL CONSIDER HOISTING A SHORT-
FUSED FLASH FLOOD WATCH.
TOMORROW / INDEPENDENCE DAY:
AT LEAST ISOLATED SHOWERS AND STORMS MAY BE ONGOING AT DAYBREAK,
THOUGH MOST GUIDANCE SUGGESTS COVERAGE SHOULD WANE BY MID-
MORNING. GLOBAL GUIDANCE THAN ADVERTISES ANOTHER UPPER-LEVEL
SHORTWAVE OR TWO PINWHEELING INTO THE AREA DURING THE AFTERNOON
HOURS, WHICH WILL SUPPORT ADDITIONAL ROUNDS OF THUNDERSTORMS. AT
THIS POINT, CONFIDENCE IN WHERE THE FRONTAL BOUNDARY (WHICH
WILL MARK THE UNSTABLE AIRMASS) WILL BE BY TOMORROW AFTERNOON
IS QUITE LOW AND DEPENDS ON COVERAGE OF STORMS TONIGHT. SO,
UNFORTUNATELY, CANNOT OFFER MORE THAN MID- RANGE CHANCE POPS
AREAWIDE TOMORROW IN FAVOR OF FURTHER REFINEMENT AS THINGS
HOPEFULLY BECOME MORE CLEAR TONIGHT. THE SAME GOES FOR SUNDAY.
BORCHARDT
BEYOND THE WEEKEND THE UPPER RIDGE BEGINS TO BUILD BACK NORTH
SLIGHTLY WITH THE EMBEDDED WAVES MOVING TO OUR NORTH. MEANWHILE
ANOTHER WAVE (OR WAVES) WILL MOVE WITHIN THE RIDGE TO OUR SOUTH
(AND POTENTIALLY STALL OUT). OVERALL THIS FAVORS SHOWER/STORM
COVERAGE FOCUSING MAINLY NORTH OR SOUTH OF THE AREA INTO MID-
WEEK. SHOWER AND STORM CHANCES RETURN LATER IN THE WEEK AS THE
RIDGE BEGINS TO BREAK DOWN AGAIN.
PETR
AVIATION /18Z TAFS THROUGH 00Z SUNDAY/
ISSUED AT 101 PM CDT FRI JUL 3 2026
KEY MESSAGES FOR THE 18Z TAF PERIOD:
* STRONG THE SEVERE THUNDERSTORMS TARGETING THE CHICAGOLAND
TERMINALS NEAR THE START OF THE TAF PERIOD. STRONG W WIND
GUSTS AND IFR VSBYS ANTICIPATED.
* ADDITIONAL THUNDERSTORMS POSSIBLE THIS AFTERNOON THROUGH THE
NIGHT WITH MUCH UNCERTAINTY IN COVERAGE BEYOND EARLY
AFTERNOON.
A MESSY LINE OF STRONG TO SEVERE THUNDERSTORMS IS TRACKING EAST
TO NORTHEAST INTO CHICAGOLAND AS OF 18Z. THESE STORMS WILL
PROGRESS ACROSS THE CHICAGOLAND SITES BETWEEN 18 AND 20Z. STRONG
WESTERLY WIND GUSTS AND HEAVY RAIN WITH IFR VSBYS ARE EXPECTED
TO ACCOMPANY THE STRONGER STORMS, WHICH SHOULD PERSIST OVER ANY
GIVEN SITE FOR BETWEEN 30 AND 60 MINUTES. WIND DIRECTION MAY GET
SQUIRRELLY IN THE VICINITY OF THUNDERSTORMS.
ADDITIONAL STORMS UPSTREAM WARRANTED A VCTS THROUGH THE
REMAINDER OF THE AFTERNOON WITH LIKELY ANOTHER ROUND OR TWO
MOVING ACROSS THE VICINITY OF THE CHICAGO SITES. UNCERTAINTY
GROWS INTO THE EVENING AND OVERNIGHT WITH ADDITIONAL SCATTERED
STORMS REMAINING POSSIBLE. A RELATIVELY BETTER WINDOW OF
OPPORTUNITY EXISTS FROM ROUGHLY 01 TO 08Z, BUT CONVECTION WILL
BE POSSIBLE ON EITHER SIDE OF THAT WINDOW. MORE GUSTY TO STRONG
WINDS AND LOWERED VSBYS WOULD BE EXPECTED WITH ANY ADDITIONAL
CONVECTION. PRECIP CHANCES DWINDLE TOWARD DAYBREAK WITH MUCH OF
SATURDAY EXPECTED TO BE DRY, ALTHOUGH THUNDERSTORM CHANCES
INCREASE AGAIN LATE AFTERNOON INTO THE EVENING.
DOOM
LOT WATCHES/WARNINGS/ADVISORIES
IL...HEAT ADVISORY UNTIL 7 PM CDT THIS EVENING FOR ILZ023-ILZ032-
ILZ033-ILZ039.
IN...HEAT ADVISORY UNTIL 7 PM CDT /8 PM EDT/ THIS EVENING FOR
INZ010-INZ011-INZ019.
LM...NONE.
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