519
FXUS63 KLOT 211134
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
634 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 /12Z TAFS THROUGH 18Z TUESDAY/
ISSUED AT 634 AM CDT MON SEP 21 2026
FORECAST CONCERNS INCLUDE...
MVFR CIGS THROUGH THIS AFTERNOON.
CHANCE OF SHOWERS THIS MORNING.
GUSTY NORTHEAST WINDS THROUGH THIS EVENING.
CIGS HAVE GENERALLY LIFTED INTO THE 2KFT RANGE, OR HIGHER AND
MVFR CIGS ARE EXPECTED TO CONTINUE THROUGH EARLY/MID AFTERNOON
BEFORE LIFTING FROM NORTHEAST TO SOUTHWEST ACROSS THE AREA.
THERE MAY BE SOME BRIEF PERIODS OF LOW MVFR CIGS BUT NOT
EXPECTING THESE TO BECOME PREVAILING.
SCATTERED SHOWERS AND DRIZZLE WILL BE POSSIBLE THIS MORNING WITH
ANY ADDITIONAL SHOWERS THIS AFTERNOON EXPECTED TO BE WEST AND
SOUTHWEST OF THE CHICAGO TERMINALS.
WINDS WILL REMAIN NORTHEAST THROUGH THE PERIOD WITH GUSTS INTO
THE LOWER/MID 20KT RANGE THROUGH THIS AFTERNOON. GUSTS WILL
BEGIN TO DIMINISH WITH SUNSET AND GUSTS MAY END FOR MOST AREAS
OVERNIGHT. 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 10 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 10 AM CDT THIS MORNING FOR BURNS
HARBOR TO MICHIGAN CITY IN.
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