972
FXUS63 KLOT 210544
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
1244 AM CDT MON SEP 21 2026
KEY MESSAGES
- SHOWERS AND DRIZZLE TO GRADUALLY DIMINISH IN COVERAGE LATE
THIS EVENING. POCKETS OF LIGHT SHOWERS/DRIZZLE MAY CONTINUE AT
TIMES TONIGHT THROUGH MIDDAY MONDAY.
- BELOW NORMAL TEMPERATURES THROUGH THE END OF THE WEEK.
DISCUSSION
ISSUED AT 1230 PM CDT SUN SEP 20 2026
A MID-LEVEL SHORTWAVE/CONVECTIVELY AUGMENTED MCV CONTINUES TO
SHIFT EAST DIRECTLY OVERHEAD EARLY THIS AFTERNOON. AT THE
SURFACE, A SYNOPTIC COLD FRONT IS PUSHING SOUTHWARD, WITH GUSTY
NORTHEASTERLY WINDS DEVELOPING IN ITS WAKE. AS THIS MCV/MID-
LEVEL WAVE PRESSES EASTWARD, THE GREATEST COVERAGE OF STEADY
SHOWERS WILL GRADUALLY PUSH EAST INTO INDIANA THROUGH LATE THIS
AFTERNOON. THE LIGHTNING THREAT HAS ENDED FOR LOCALES NORTH OF
I-80, AS THE MAIN ELEVATED INSTABILITY AXIS CONTINUES TO MOVE
SOUTHWARD. CAN'T RULE OUT A FEW BONAFIDE THUNDERSTORMS
DEVELOPING ACROSS OUR FAR SOUTH (FORD - BENTON COUNTIES) THIS
AFTERNOON ALONG THE COLD FRONT. FORECAST EFFECTIVE INFLOW LAYERS
ARE VERY SHALLOW, GREATLY LIMITING AVAILABLE SRH, BUT DEEP
LAYER SHEAR VALUES NEAR 35 KTS COULD POTENTIALLY SUPPORT A FEW
MINI SUPERCELLS. THE WINDOW FOR THIS WILL BE VERY BRIEF, PERHAPS
3-6 PM (IF THAT), WITH THE MAIN POTENTIAL FOCUSING EAST AND
SOUTH OF OUR FORECAST AREA.
SINCE LOW-LEVEL MOISTURE WON'T REALLY GO ANYWHERE TONIGHT,
POCKETS OF LIGHT SHOWERS/DRIZZLE WILL BE POSSIBLE INTO MONDAY
MORNING AS ADDITIONAL VORTICITY MAXIMA MEANDER OVERHEAD. CLOUD
BASES MAY LIFT SUFFICIENTLY MONDAY AFTERNOON TO BRING AN END TO
LINGERING PRECIPITATION, BUT ADDITIONAL DISTURBANCES DRIFTING
ATOP THE FRONTAL ZONE MAY RESULT IN SPORADIC SPRINKLES/LIGHT
PRECIP CHANCES INTO TUESDAY. PERSISTENT STRONG NORTHEASTERLY
WINDS WILL RESULT IN A PROLONGED PERIOD OF DANGEROUS SWIMMING
CONDITIONS AT AREA BEACHES DUE TO HIGH WAVES AND STRONG
CURRENTS.
THEREAFTER, WE'LL GET A NOTABLE INJECTION OF DRIER AIR FROM THE
EAST AS HIGH PRESSURE SETTLES ACROSS THE UPPER MIDWEST AND
GREAT LAKES REGION THROUGH THE MID AND END OF THE WEEK.
SEASONABLY COOL AND PLEASANT CONDITIONS LOOK TO PREVAIL DURING
THIS PERIOD, WITH HIGH TEMPERATURES GENERALLY IN THE 60S WITH A
VERY MODEST WARMING TREND INTO WEEK'S END. UPPER-LEVEL BLOCKING
LOOKS LIKE IT'LL HOLD MOST PRECIPITATION CHANCES TO A MINIMUM,
AT LEAST UNTIL NEXT WEEKEND WHEN A SMALL SIGNAL FOR
PRECIPITATION CHANCES MAY RETURN.
CARLAW
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.
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