597
FXUS63 KLOT 200724
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
224 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 /06Z TAFS THROUGH 12Z MONDAY/
ISSUED AT 103 AM CDT SUN SEP 20 2026
KEY AVIATION FORECAST MESSAGES:
- PERIOD OF TSRA ACROSS THE REGION THROUGH DAYBREAK. ADDITIONAL
SHRA LINGER THROUGH MIDDAY/EARLY AFTERNOON.
- IFR CIGS/VIS LIKELY INTO MIDDAY BEFORE GRADUALLY IMPROVING,
WITH A PERIOD OF AT LEAST INTERMITTENT LIFR POSSIBLE THROUGH
THE PREDAWN HOURS THIS MORNING.
- NORTHEAST WINDS GRADUALLY INCREASE TOWARD/JUST AFTER DAYBREAK
AND BECOME GUSTY IN THE 20-25 KT RANGE ESPECIALLY FROM MIDDAY
INTO TONIGHT.
A SERIES OF MID-LEVEL DISTURBANCES WILL TRACK ACROSS THE REGION
THROUGH THIS AFTERNOON, PROVIDING MOIST ASCENT FOR HEAVY
CONVECTIVE SHRA/TSRA NORTH OF A STATIONARY FRONTAL ZONE ACROSS
NORTHERN IL/IN. TSRA THREAT LOOKS TO FOCUS IN THE I-88/I-80
CORRIDORS THROUGH ABOUT DAYBREAK WITH MDW/GYY MOST LIKELY TO
HAVE DIRECT IMPACTS, THOUGH AT LEAST SCATTERED TS MAY GET AS FAR
AS RFD AND C90 CHICAGO TRACON AIRSPACE WILL BE AFFECTED.
THUNDER THREAT APPEARS TO SHIFT SOUTH OF THE TERMINALS BEYOND
DAYBREAK, THOUGH CONVECTIVE SHRA WILL PERSIST (POSSIBLY WITH
AREAS OF DRIZZLE AS WELL) WHILE GRADUALLY BECOME MORE SCATTERED
THIS AFTERNOON.
WITH SEVERAL ROUNDS OF SHOWERS LOW-LEVELS HAVE BECOME FAIRLY
SATURATED, RESULTING IN AREAS OF LIFR CIGS AT ISSUANCE TIME
ESPECIALLY FROM RFD/ORD NORTH AND NORTHEAST AT ISSUANCE TIME.
MODEL GUIDANCE CONTINUES TO HIT IFR (CIGS AND VIS) PRETTY HARD
THROUGH MIDDAY/EARLY AFTERNOON, WITH LIFR CIGS DURING THE
PREDAWN HOURS (THOUGH MAY BE PATCHY AS SHRA/TS MIX THINGS UP A
BIT). IMPROVEMENT TO MVFR MAY NOT OCCUR UNTIL LATER THIS
AFTERNOON OR EVEN TOWARD EVENING.
LIGHT EAST/VARIABLE WINDS WILL TURN NORTHEAST PREDAWN AS A WEAK
SURFACE LOW PRESSURE WAVE PASSES SOUTH OF THE TERMINALS. WINDS
WILL BEGIN TO STRENGTHEN AROUND/AFTER DAYBREAK AS THE GRADIENT
TIGHTENS IN RESPONSE TO HIGH PRESSURE BUILDING ACROSS ONTARIO
AND THE NORTHERN GREAT LAKES. GUSTS OF 20-25 KTS LIKELY BY
AFTERNOON, WITH A FEW HIGHER GUSTS POSSIBLE ESPECIALLY LATER
THIS AFTERNOON AND EVENING.
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 FROM 7 AM CDT THIS MORNING 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 FROM 7 AM THIS MORNING TO 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.
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