997
FXUS63 KLOT 201132
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
632 AM CDT SUN SEP 20 2026
KEY MESSAGES
- A FLOOD WATCH FOR FLASH FLOODING HAS BEEN EXTENDED THROUGH
EARLY THIS AFTERNOON FOR AREAS ROUGHLY ALONG AND NORTH OF THE
ILLINOIS AND KANKAKEE RIVERS.
- PERIODS OF SHOWERS AND THUNDERSTORMS WITH TORRENTIAL RAIN AND
LOCALIZED FLASH FLOODING ARE EXPECTED THROUGH MIDDAY TODAY.
- BELOW NORMAL TEMPS THROUGH THE END OF THE WEEK.
DISCUSSION
ISSUED AT 224 AM CDT SUN SEP 20 2026
THE FLOOD WATCH HAS BEEN EXTENDED UNTIL 18Z TODAY. PERIODS OF
SHOWERS AND THUNDERSTORMS ARE EXPECTED TO CONTINUE THROUGH AT
LEAST MID MORNING FOR MUCH OF THE WATCH AREA. THE MAIN SURFACE
LOW WON'T REACH CENTRAL IN UNTIL THIS AFTERNOON AND THIS MAY
KEEP PERSISTENT MODERATE/HEAVY RAINS ACROSS PARTS OF THE AREA
THROUGH MIDDAY. AND EVEN FROM THIS SHORT(ER) DISTANCE, THERE IS
STILL SOME UNCERTAINTY WHERE THE HEAVIEST RAINS MAY FALL. THE
CURRENT ACTIVITY MAY FAVOR THE I-80 CORRIDOR IN THE NEXT FEW
HOURS AND THE NEXT WAVE OVER EASTERN IA MAY FAVOR AREAS ALONG
AND NORTH OF I-80 WITH PERHAPS LATER WAVES THIS MORNING FAVORING
AREAS SOUTH OF I-80. WITH ALL THIS IN MIND, OPTED TO EXTEND THE
FLOOD WATCH THROUGH 18Z AND AS TRENDS EMERGE, THE WATCH CAN BE
CANCELLED AS NEEDED LATER THIS MORNING. AS FOR RAINFALL AMOUNTS,
THERE COULD BE ONE OR TWO SWATHS OF 3-5 INCHES OF RAIN BY THE
TIME IT ENDS LATER TODAY, WHICH COULD LEAD TO FLASH FLOODING.
SHOWERS AND SCATTERED THUNDERSTORMS MAY STILL BE MOVING ACROSS
THE SOUTHEAST CWA LATER THIS AFTERNOON INTO EARLY THIS EVENING
BEFORE PRECIPITATION FINALLY COMES TO AN END. THERE MAY BE
LINGERING SHOWERS TONIGHT AND PERHAPS A FEW SHOWERS ON MONDAY,
BUT ONLY ISOLATED COVERAGE EXPECTED.
FOG DEVELOPED OVER SOUTHERN LAKE MICHIGAN SATURDAY EVENING AND
BRIEFLY MOVED ONSHORE ALONG THE IL SHORE. WEBCAMS SUGGEST THE
VISIBILITIES HAVE IMPROVED RIGHT NEAR LAKE MICHIGAN AND AS
NORTHERLY WINDS SLOWLY INCREASE THROUGH THE MORNING, THIS FOG
MAY LIFT INTO A LOW CLOUD CEILING. FOG OVER LAKE MICHIGAN IS
ALSO EXPECTED TO SLOWLY LIFT AS WELL, THOUGH PERHAPS NOT UNTIL
THE WINDS INCREASE FURTHER LATER THIS MORNING.
STRONG NORTHEAST WINDS WILL DEVELOP TODAY AND REMAIN STRONG
THROUGH WEDNESDAY PRODUCING HIGH WAVES AND DANGEROUS SWIMMING
CONDITIONS AT LAKE MICHIGAN BEACHES.
STILL QUITE A BIT OF UNCERTAINTY FOR A POSSIBLE UPPER LOW AND
SHOWER CHANCES THIS WEEK. TEMPERATURES LOOK TO BE WELL BELOW
NORMAL FOR THE END OF SEPTEMBER WITH HIGH TEMPS MAINLY IN THE
60S THROUGH THURSDAY. CMS
AVIATION /12Z TAFS THROUGH 18Z MONDAY/
ISSUED AT 632 AM CDT SUN SEP 20 2026
KEY AVIATION FORECAST MESSAGES:
- TSRA THREAT DECREASING RAPIDLY EARLY THIS MORNING, THOUGH
RA/SHRA WILL PERSIST THROUGH MID-LATE MORNING BEFORE BECOMING
MORE SCATTERED SHRA THIS AFTERNOON.
- IFR CIGS LIKELY THROUGH MIDDAY, WITH SOME PATCHY LIFR POSSIBLE
EARLY. GRADUAL IMPROVEMENT TO MVFR LATER THIS AFTERNOON.
- NORTHEAST WINDS INCREASE THIS MORNING AND BECOME BLUSTERY THIS
AFTERNOON/TONIGHT WITH GUSTS AROUND 25 KTS, POSSIBLY A BIT
HIGHER AT TIMES.
TSRA HAVE POSHED THROUGH THE TERMINALS JUST PRIOR TO 12Z, WITH
LIGHTNING THREAT NOW GREATLY DIMINISHED. AN AREA OF RA/SHRA
EXTENDING BACK INTO FAR EASTERN IA WILL PERSIST ACROSS THE AREA
THROUGH MID/LATE MORNING HOWEVER, BEFORE TAPERING TO LIGHTER
SCATTERED SHOWERS MIDDAY/EARLY AFTERNOON. CAN'T RULE OUT SOME
SPOTTY LIGHT SHOWERS AT TIMES TONIGHT INTO EARLY MONDAY, THOUGH
COVERAGE ~20% TOO LOW FOR TAF INCLUSION.
EXTENSIVE IFR/LIFR CIGS ACROSS THE AREA PREDAWN HAVE SCATTERED
OUT IN SPOTS IN THE WAKE OF THE HEAVIER CONVECTION, THOUGH IFR
CIGS LIKELY TO REDEVELOP/PERSIST AND CONTINUE INTO THE AFTERNOON
BEFORE IMPROVING TO MVFR LATE. MVFR CIGS WILL LIKELY PERSIST
OVERNIGHT AND INTO MONDAY MORNING, THOUGH MAY SCATTER TO VFR AT
TIMES LATE.
SURFACE PRESSURE GRADIENT WILL TIGHTEN THIS MORNING AS HIGH
PRESSURE BUILDS ACROSS ONTARIO AND THE NORTHERN LAKES, RESULTING
IN INCREASING NORTHEAST WINDS. WINDS WILL BECOME GUSTY LATER
THIS MORNING WITH GUSTS AROUND 25 KTS (POSSIBLY OCCASIONALLY A
LITTLE HIGHER) EXPECTED LATER THIS AFTERNOON AND TONIGHT. BREEZY
NORTHEAST FLOW WILL CONTINUE INTO MONDAY.
RATZER
LOT WATCHES/WARNINGS/ADVISORIES
IL...FLOOD WATCH UNTIL 1 PM CDT THIS AFTERNOON FOR ILZ003-ILZ004-
ILZ005-ILZ006-ILZ008-ILZ010-ILZ011-ILZ012-ILZ013-ILZ019-
ILZ020-ILZ021-ILZ023-ILZ103-ILZ104-ILZ105-ILZ106-ILZ107-
ILZ108.
BEACH HAZARDS STATEMENT THROUGH TUESDAY EVENING FOR ILZ006-
ILZ103-ILZ104.
IN...FLOOD WATCH UNTIL 1 PM CDT THIS AFTERNOON FOR INZ001-INZ002.
BEACH HAZARDS STATEMENT FROM 10 AM CDT THIS MORNING THROUGH
TUESDAY EVENING FOR INZ001.
BEACH HAZARDS STATEMENT FROM 10 AM CDT THIS MORNING THROUGH
MONDAY MORNING FOR INZ002.
LM...DENSE FOG ADVISORY UNTIL 9 AM CDT THIS MORNING FOR THE IL AND
IN NEARSHORE WATERS.
SMALL CRAFT ADVISORY UNTIL 7 PM CDT TUESDAY FOR THE IL
NEARSHORE WATERS.
SMALL CRAFT ADVISORY FROM 10 AM THIS MORNING TO 7 PM CDT
TUESDAY FOR CALUMET HARBOR IL TO BURNS HARBOR IN.
SMALL CRAFT ADVISORY FROM 1 PM THIS AFTERNOON TO 7 AM CDT
MONDAY FOR BURNS HARBOR TO MICHIGAN CITY IN.
VISIT US AT WEATHER.GOV/CHICAGO
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page