646
FXUS63 KLOT 112013
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
313 PM CDT TUE AUG 11 2026
KEY MESSAGES
- AFTERNOON SHOWERS/STORMS EXPECTED TO WANE INTO THIS EVENING.
- ANOTHER ROUND OF SHOWERS/STORMS POSSIBLE TONIGHT (20-30%),
INCLUDING THE POTENTIAL FOR SEVERE STORMS AND HEAVY RAINFALL.
- ADDITIONAL STRONG/SEVERE STORMS POSSIBLE WEDNESDAY.
DISCUSSION
ISSUED AT 310 PM CDT TUE AUG 11 2026
ONGOING SCATTERED SHOWERS AND STORMS WILL LINGER THIS AFTERNOON
AND EARLY EVENING IN THE WAKE OF SIGNIFICANT SEVERE WEATHER
EARLIER TODAY. THIS ACTIVITY IS EXPECTED TO WANE OVER THE NEXT
SEVERAL HOURS WITH CONVECTIVE INHIBITION/SUBSIDENCE IN PLACE
ACROSS THE CWA AS THE REINFORCED SURFACE BOUNDARY HAS PUSHED SOUTH
OF THE AREA ACROSS CENTRAL ILLINOIS.
WHILE THIS WILL LIKELY LEAD TO A LULL IN SHOWER/STORM CHANCES THIS
EVENING, ADDITIONAL THUNDERSTORM DEVELOPMENT WILL BE POSSIBLE
OVERNIGHT TONIGHT -- PRIMARILY ACROSS NORTHEAST ILLINOIS/NORTHWEST
INDIANA, INCLUDING THE CHICAGO AREA. THE AFOREMENTIONED BOUNDARY
IS EXPECTED TO WORK BACK NORTH ACROSS THE AREA WITH TIME THIS
EVENING WITH SHOWERS/STORMS POSSIBLY TRAINING ALONG/NORTH OF SAID
BOUNDARY. STRONG BUOYANCY ALOFT ON THE ORDER OF 3,500+ MUCAPE
COMBINED WITH DEEP-LAYER SHEAR ~35 KTS WILL SUPPORT A CONTINUED
THREAT FOR STRONG/SEVERE STORMS TONIGHT. GIVEN ANTICIPATED
CONVECTIVE EVOLUTION/TRAINING OF STORMS, PERHAPS OF EQUAL CONCERN
WILL BE THE POTENTIAL FOR HEAVY RAINFALL/FLOODING LATER TONIGHT.
STORMS IN AN ENVIRONMENT CHARACTERIZED BY ~2" PWATS WOULD LEAD TO
VERY EFFICIENT RAINFALL, AND POTENTIALLY BRING AN ADDITIONAL 1-2"+
OF RAIN TO AREAS THAT ALREADY SAW HEAVY RAINFALL EARLIER IN THE
DAY. WHILE UNCERTAINTY REMAINS RELATIVELY HIGH AT THIS TIME
(20-30% POPS TONIGHT), ANOTHER ROUND OF IMPACTFUL STORMS REMAINS
POSSIBLE TONIGHT.
THE AFOREMENTIONED BOUNDARY IS EXPECTED TO REMAIN DRAPED ACROSS
THE AREA DURING THE DAY WEDNESDAY WITH AMPLE INSTABILITY IN PLACE
ALONG AND TO ITS SOUTH, SUPPORTING CONTINUED THUNDERSTORM CHANCES
WEDNESDAY MORNING INTO WEDNESDAY EVENING. DAMAGING WINDS WILL BE
THE PRIMARY THREAT WITH STRONGEST STORMS, ESPECIALLY IF ANOTHER
LINE ORGANIZES AND TRACKS FROM NORTHWEST TO SOUTHEAST ACROSS THE
WARM SECTOR SOUTH OF THE FRONT DURING THE DAY. HAIL AND LOCALLY
HEAVY RAINFALL WILL ALSO BE POSSIBLE.
PRECISE DETAILS IN REGARDS TO TIMING AND IMPACTS BECOMES MORE
OBSCURE BEYOND WEDNESDAY, BUT ADDITIONAL ROUNDS OF THUNDERSTORMS
WILL BE POSSIBLE INTO THE END OF THE WEEK AS THE BOUNDARY LINGERS
ACROSS THE AREA AND KEEPS A WARM, MOIST AIRMASS IN PLACE WITH
RELATIVELY STRONG NORTHWEST FLOW ALOFT. A MORE SUBSTANTIAL BREAK
IN STORM CHANCES MAY NOT COME UNTIL LATE THIS UPCOMING WEEKEND OR
EARLY NEXT WEEK AS SURFACE HIGH PRESSURE MAY SETTLE MORE FIRMLY
OVER THE MIDWEST.
CORNISH
AVIATION /18Z TAFS THROUGH 00Z THURSDAY/
ISSUED AT 1253 PM CDT TUE AUG 11 2026
MAINLY VFR CONDITIONS THIS AFTERNOON, BUT DO EXPECT
REDEVELOPMENT AT SOME POINT (ALREADY SEEING SOME ACROSS IA AS
OF 1740Z) AND WILL NEED TO MONITOR THIS FOR THE REST OF THE
AFTERNOON. CURRENTLY HAVE VCTS IN FOR 23Z-2Z TIMEFRAME FOR THIS
IDEA. WINDS LIKELY GO LIGHT OVERNIGHT WITH CIGS TRENDING DOWN
WITH POTENTIAL FOR LIFR CONDITIONS ESP TOWARD DAYBREAK, WHETHER
FG/BR OR LOW STRATUS...AND THINK THIS WILL TRY TO MIX TO VFR
AGAIN TOWARD DAYBREAK. NOT IMPOSSIBLE THERE COULD BE ANOTHER
ROUND OF TSRA BETWEEN 6-12Z BUT VERY LOW CONFIDENCE IN THIS
ATTM. WINDS PRIMARILY LIGHT AND E/NE THRU PERIOD BUT COULD GO
MORE S AT GYY IF LAKE/LAND BREEZES DEVELOP.
LOT WATCHES/WARNINGS/ADVISORIES
IL...LAKESHORE FLOOD WARNING UNTIL 5 PM CDT THIS AFTERNOON FOR
ILZ104.
IN...LAKESHORE FLOOD WARNING UNTIL 5 PM CDT THIS AFTERNOON FOR
INZ001-INZ002.
LM...NONE.
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