991
FXUS63 KLOT 190648
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
148 AM CDT SAT SEP 19 2026
KEY MESSAGES
- A FLOOD WATCH FOR FLASH FLOODING IS IN EFFECT FOR MUCH OF
NORTHERN ILLINOIS AND FAR NORTHWEST INDIANA THROUGH EARLY THIS
AFTERNOON.
- PERIODS OF HEAVY RAIN AND SCATTERED THUNDERSTORMS THROUGH
MID/LATE THIS MORNING AND THEN A SECOND WAVE OF HEAVY RAIN AND
SCATTERED THUNDERSTORMS TONIGHT INTO SUNDAY. LOCALIZED FLASH
FLOODING WILL BE POSSIBLE WHERE THE HEAVIEST RAINS OCCUR OVER
THE SAME AREAS.
- BELOW NORMAL TEMPS EARLY/MID NEXT WEEK WITH LOW CHANCES FOR
SHOWERS.
DISCUSSION
ISSUED AT 148 AM CDT SAT SEP 19 2026
PRIMARY FORECAST FOCUS AND CHALLENGE REMAINS HEAVY RAIN TIMING
AND LOCATION THROUGH SUNDAY.
A LARGE AREA OF CONVECTION CURRENTLY EXTENDS FROM FAR NORTHEAST
IA ACROSS MOST OF SOUTHERN WI AND IS SLOWLY DRIFTING SOUTH INTO
FAR NORTHERN IL. THIS ACTIVITY WILL CONTINUE TO SLOWLY MOVE
INTO NORTHERN IL DURING THE PREDAWN HOURS AND INTO THE I-80
CORRIDOR BY MID/LATE MORNING. THERE REMAINS SOME UNCERTAINTY
FOR WHERE THE HEAVIEST RAINS WILL SETUP AND HOW LONG THEY'LL
PERSIST IN ANY GIVEN AREA. THE HEAVIEST RAINS THIS MORNING MAY
END UP FALLING ALONG AND NORTHEAST OF A ROCKFORD TO CHICAGO
LINE. SCATTERED SHOWERS AND POSSIBLY A THUNDERSTORM MAY CONTINUE
THIS AFTERNOON. CURRENT FLOOD WATCH AREA HAS THIS THREAT
HANDLED WELL BOTH FOR AREA AND TIMING, ENDING AT 18Z TODAY AND
NO CHANGES ARE PLANNED.
ANOTHER PERIOD OF THUNDERSTORMS WITH HEAVY RAIN IS EXPECTED
LATER THIS EVENING, THROUGH THE OVERNIGHT HOURS AND INTO SUNDAY
MORNING, LIKELY SLOWLY SAGGING SOUTH ACROSS THE CWA DURING THIS
TIME PERIOD, WHICH MAY BRING THE HEAVIEST AND MOST WIDESPREAD
RAINS TO AT LEAST PARTS OF THE AREA. WHERE THESE MAY OVERLAP
WITH HEAVY RAINS FROM THIS MORNING IS STILL UNCERTAIN. ANOTHER
FLOOD WATCH IS LIKELY FROM LATE THIS EVENING INTO SUNDAY
MORNING, FOR THE SAME AREAS AS THE CURRENT WATCH AND POSSIBLY
EXTENDING ANOTHER ROW OF COUNTIES SOUTH TO THE ILLINOIS AND
KANKAKEE RIVER VALLEYS. GIVEN THE CURRENT WATCH END TIME AND A
LARGE TIME GAP UNTIL THE NEXT WAVE TONIGHT, WILL HOLD OFF ON A
NEW FLOOD WATCH FOR TONIGHT.
THE NEW SPC DAY1 AND DAY2 OUTLOOKS HAVE TRIMMED THE LEVEL 1
SEVERE RISK TO THE FAR SOUTHERN PORTIONS OF THE LOCAL AREA.
THERE WILL STILL BE THE POTENTIAL FOR A FEW STRONGER STORMS AND
PERHAPS AN ISOLATED SEVERE STORM OR TWO, MAINLY ACROSS THE
SOUTHERN CWA.
A FEW OF THE MODELS, NAM/HRRR, SUGGEST ANOTHER PERIOD OF HEAVY
RAIN DURING THE DAY ON SUNDAY. CONFIDENCE IS LOW DURING THIS
PERIOD, BUT IF THESE TRENDS WERE TO CONTINUE, A SECOND POSSIBLE
FLOOD WATCH MAY NEED TO BE EXTENDED OUT INTO THIS TIME PERIOD AS
WELL.
HIGH WAVES AND DANGEROUS SWIMMING CONDITIONS WILL CONTINUE INTO
THIS AFTERNOON AT IL LAKE MICHIGAN BEACHES AS EASTERLY WINDS
TURN MORE SOUTHEASTERLY. NORTHEAST WINDS ARE EXPECTED TO QUICKLY
INCREASE EARLY SUNDAY MORNING AND THEN REMAIN FAIRLY STRONG
THROUGH THE MIDDLE OF NEXT WEEK, RESULTING IN SEVERAL DAYS OF
HIGH WAVES AND DANGEROUS SWIMMING CONDITIONS AT IL AND IN LAKE
MICHIGAN BEACHES. AN ADDITIONAL BEACH HAZARD STATEMENT WILL BE
NEEDED FOR THIS LONG TIME PERIOD.
THE MODELS ARE NOW TRENDING TOWARD AN UPPER LEVEL LOW ACROSS THE
REGION THROUGH MIDWEEK. WHILE BELOW NORMAL TEMPERATURES STILL
LOOK ON TRACK, THERE WILL LIKELY BE AT LEAST LOW CHANCES FOR
SHOWERS, ESPECIALLY DURING THE AFTERNOON/EVENING AS VARIOUS WEAK
WAVES ROTATE AROUND THE UPPER LOW. CMS
AVIATION /06Z TAFS THROUGH 12Z SUNDAY/
ISSUED AT 1234 AM CDT SAT SEP 19 2026
KEY AVIATION FORECAST MESSAGES:
- SHRA/TSRA DEVELOP INTO FAR NORTHERN IL 07-10Z THIS MORNING
WITH TSRA AND NEAR-LIFR VISIBILITY IN HEAVY RAIN THROUGH MUCH
OF THE MORNING.
- SHRA AND MVFR CEILINGS PERSIST AT TIMES THIS AFTERNOON INTO
TONIGHT, WITH ANOTHER ROUND OF TSRA POSSIBLE THIS EVENING INTO
THE OVERNIGHT HOURS.
SHRA/TSRA CONTINUE TO DEVELOP ACROSS SOUTHERN WI IN RESPONSE TO
LOW-LEVEL JET FORCING ATOP AN ELEVATED WARM FRONTAL ZONE.
GUIDANCE REMAINS IN GOOD AGREEMENT THAT THIS CONVECTION WILL
CONTINUE TO DEVELOP EAST-SOUTHEASTARD OVER THE NEXT FEW HOURS
AND IMPACT THE TERMINALS FOR A PROLONGED PERIOD INTO MID-LATE
MORNING. WHILE TS COVERAGE SHOULD DIMINISH BY MIDDAY, SCATTERED
SHRA MAY PERSIST AS WEAK, MOIST ASCENT PERSISTS WITHIN THE
WARM FRONTAL ZONE. ANOTHER MID-LEVEL WAVE CURRENTLY EMERGING
FROM THE HIGH PLAINS IS PROGGED TO APPROACH THE FORECAST AREA
FROM THE WEST THIS EVENING, WITH ANOTHER INCREASE IN SHRA AND
TSRA COVERAGE LIKELY TONIGHT.
MVFR CEILINGS (ALREADY IN PLACE AT RFD AT ISSUANCE) ARE
EXPECTED TO BECOME WIDESPREAD THIS MORNING AND PERSIST THROUGH
THE PERIOD, WITH IFR CIGS POSSIBLE AT TIMES. IFR TO NEAR-LIFR
VSBYS ARE POSSIBLE IN HEAVIER SHRA/TSRA THIS MORNING AND AGAIN
TONIGHT.
SURFACE WINDS ARE EXPECTED TO REMAIN GENERALLY EAST-SOUTHEAST TO
SOUTHEAST ACROSS THE TERMINALS, THOUGH MAY BECOME MORE SOUTHERLY
AT RFD (AND POSSIBLY DPA) LATER TODAY DEPENDING ON HOW FAR
NORTH A SURFACE LOW PRESSURE WAVE AND SURFACE WARM FRONT LIFT
INTO THE REGION. TSRA MAY ALSO TEMPORARILY PRODUCE GUSTY, MORE
NORTHERLY SURFACE WINDS.
RATZER
LOT WATCHES/WARNINGS/ADVISORIES
IL...FLOOD WATCH THROUGH THIS AFTERNOON FOR ILZ003-ILZ004-ILZ005-
ILZ008.
BEACH HAZARDS STATEMENT THROUGH THIS EVENING FOR ILZ006.
FLOOD WATCH FROM 4 AM CDT EARLY THIS MORNING THROUGH THIS
AFTERNOON FOR ILZ006-ILZ010-ILZ011-ILZ012-ILZ013-ILZ020-
ILZ103-ILZ104-ILZ105-ILZ106.
BEACH HAZARDS STATEMENT THROUGH THIS AFTERNOON FOR ILZ103-
ILZ104.
IN...FLOOD WATCH FROM 4 AM CDT EARLY THIS MORNING THROUGH THIS
AFTERNOON FOR INZ001-INZ002.
LM...SMALL CRAFT ADVISORY UNTIL 3 PM CDT THIS AFTERNOON FOR
WINTHROP HARBOR TO NORTHERLY IS. IL.
VISIT US AT WEATHER.GOV/CHICAGO
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page