216
FXUS63 KLOT 210635
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
135 AM CDT MON SEP 21 2026
KEY MESSAGES
- PATCHY SHOWERS AND LIGHT DRIZZLE AT TIMES INTO TUESDAY
MORNING.
- DRY, BUT WITH BELOW AVERAGE TEMPERATURES FOR MUCH OF THE
REMAINDER OF THE WORK WEEK.
DISCUSSION
ISSUED AT 135 AM CDT MON SEP 21 2026
THE SURFACE COLD FRONT HAS SETTLED SOUTH OF THE AREA ACROSS
DOWNSTATE IL/IN AND THE OHIO VALLEY THIS MORNING, WHILE A BROAD
AREA OF SURFACE HIGH PRESSURE WAS BUILDING ACROSS WESTERN
ONTARIO AND THE FAR NORTHERN GREAT LAKES. THOUGH THE SURFACE
FRONTAL ZONE IS WELL SOUTH OF THE AREA, THE FORECAST AREA
REMAINS BENEATH THE NORTHERN PERIPHERY OF THE ASSOCIATED
ELEVATED BAROCLINIC ZONE. SEVERAL MINOR MID-LEVEL VORT CENTERS
ARE EXPECTED TO PROPAGATE EAST ALONG THE UPPER LEVEL FRONTAL
ZONE TODAY, WHICH COMBINED WITH LINGERING MOISTURE AND TRANSIENT
WEAK MID-LEVEL F-GEN WILL RESULT IN PERSISTENT CLOUD COVER AND
SOME LIGHT DRIZZLE AND SPOTTY SHOWERS AT TIMES TODAY. BREEZY
NORTHEAST SURFACE WINDS GUSTING 25 TO 30 MPH WILL RESULT IN
COOLER THAN AVERAGE TEMPERATURES IN THE 60S, AND WILL ALSO
MAINTAIN HIGH WAVES AND HAZARDOUS SWIM CONDITIONS AT OUR LAKE
MICHIGAN BEACHES FOR THE NEXT SEVERAL DAYS.
SHOWER CHANCES WILL CONTINUE (OR REDEVELOP) MAINLY WEST OF THE
FOX VALLEY ACROSS NORTHERN IL TONIGHT INTO TUESDAY MORNING, AS
AN UPPER LEVEL LOW DRIFTS EAST FROM THE PLAINS TO THE WESTERN
GREAT LAKES. THE EASTWARD EXTENT OF THESE SHOWERS LOOKS TO BE
SLOWED/BLOCKED BY THE CONTINUED FEED OF GRADUALLY DRIER LOW-
LEVEL AIR THANKS TO THE NORTHEAST SURFACE WINDS.
THE UPPER LOW WILL THEN GRADUALLY DRIFT EAST-SOUTHEAST ACROSS
IN/OH AND TUESDAY NIGHT THROUGH WEDNESDAY, WHILE THE
SOUTHWESTERN PERIPHERY OF THE SURFACE HIGH TO OUR
NORTH/NORTHEAST SETTLES ACROSS THE WESTERN LAKES AND BRINGS MORE
SUBSTANTIALLY DRIER AIR TO THE AREA DURING THE MID-LATE WEEK
PERIOD. DESPITE DIMINISHING NORTHEAST WINDS, COOLER THAN AVERAGE
TEMPERATURES ARE EXPECTED TO PERSIST WITH DAYTIME HIGHS
GENERALLY IN THE 60S AND NIGHTTIME LOWS IN THE 40S (LOWER 50S IN
CHICAGO). A GRADUAL WARM-UP BACK INTO THE LOW-70S LOOKS TO
OCCUR NEXT WEEKEND AS MEDIUM-RANGE GUIDANCE AND ENSEMBLES
DEVELOP UPPER RIDGING BACK INTO THE UPPER MIDWEST. THERE REMAINS
A SIGNAL FOR PRECIPITATION CHANCES TO RETURN TO PARTS OF THE
UPPER MIDWEST LATE IN THE WEEKEND, THOUGH A DEEP UPPER TROUGH
ALONG THE EAST COAST MAY HOLD MORE MEANINGFUL CHANCES WEST OF
THE AREA UNTIL EARLY NEXT WEEK.
RATZER
AVIATION /06Z TAFS THROUGH 12Z TUESDAY/
ISSUED AT 1244 AM CDT MON SEP 21 2026
FORECAST CONCERNS INCLUDE...
PATCHY IFR CIGS EARLY THIS MORNING, THEN MVFR CIGS THRU MIDDAY.
AREAS OF LIGHT FOG AND DRIZZLE THROUGH MID MORNING.
GUSTY NORTHEAST WINDS THROUGH THIS EVENING.
AREAS OF DRIZZLE WILL PERSIST THROUGH MID MORNING, THOUGH MAY
BECOME LESS PREVAILING AFTER DAYBREAK. THERE WILL REMAIN A
CHANCE FOR ISOLATED SHOWERS THROUGH THIS AFTERNOON. IFR CIGS ARE
SLOWLY LIFTING INTO LOW MVFR AND EXPECT LOW MVFR CIGS TO
CONTINUE THROUGH MID MORNING AND THEN CIGS WILL LIFT INTO LOW
VFR THIS AFTERNOON, THOUGH ONLY MEDIUM CONFIDENCE ON TIMING.
NORTHEAST WINDS WILL CONTINUE THROUGH THE PERIOD WITH SPEEDS IN
THE 10-15KT RANGE AND GUSTS INTO THE 20-25KT RANGE. SPEEDS AND
GUSTS WILL SLOWLY DIMINISH THIS EVENING WITH GUSTS POSSIBLY
ENDING FOR MOST AREAS BY LATE THIS EVENING AND ESPECIALLY INTO
EARLY TUESDAY MORNING. CMS
LOT WATCHES/WARNINGS/ADVISORIES
IL...BEACH HAZARDS STATEMENT THROUGH WEDNESDAY EVENING FOR ILZ006-
ILZ103-ILZ104.
IN...BEACH HAZARDS STATEMENT THROUGH WEDNESDAY AFTERNOON FOR INZ001.
BEACH HAZARDS STATEMENT UNTIL 7 AM CDT THIS MORNING FOR INZ002.
LM...SMALL CRAFT ADVISORY UNTIL 7 PM CDT WEDNESDAY FOR THE IL
NEARSHORE WATERS.
SMALL CRAFT ADVISORY UNTIL 10 AM CDT WEDNESDAY FOR CALUMET
HARBOR IL TO BURNS HARBOR IN.
SMALL CRAFT ADVISORY UNTIL 7 AM CDT THIS MORNING FOR BURNS
HARBOR TO MICHIGAN CITY IN.
VISIT US AT WEATHER.GOV/CHICAGO
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page