921
FXUS63 KLOT 170526
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
1226 AM CDT SAT OCT 17 2026
KEY MESSAGES
- LAKE EFFECT SHOWERS ARE EXPECTED TO PERSIST IN NORTHWEST
INDIANA THROUGH DAYBREAK.
- COLDEST NIGHT OF THE SEASON EXPECTED TONIGHT WITH LOWS
NEAR/JUST BELOW FREEZING ACROSS INTERIOR PORTIONS OF NORTHERN
IL.
- DRY AND MILD WEATHER RETURNS SUNDAY AND PERSISTS NEXT WEEK.
DISCUSSION
ISSUED AT 133 PM CDT FRI OCT 16 2026
A SEASONABLY STRONG AND EXPANSIVE HIGH-PRESSURE SYSTEM OVER THE
GREAT PLAINS CONTINUES TO BUILD EASTWARD INTO THE MIDWEST THIS
AFTERNOON, FOLLOWING A SURFACE LOW MOVING INTO NEW ENGLAND.
STRONG NORTHERLY WINDS BETWEEN THESE SYSTEMS ARE PUSHING THE
SEASON'S COLDEST AIRMASS SOUTHWARD INTO THE AREA, RESULTING IN A
CLOUDY, CHILLY, AND BREEZY DAY ACROSS THE REGION. A FEW WIDELY
SCATTERED SHOWERS REMAIN POSSIBLE ACROSS NORTHERN ILLINOIS
THROUGH SUNSET AS AN UPPER-LEVEL TROUGH MOVES OVERHEAD. HOWEVER,
SHOWER ACTIVITY WILL PRIMARILY CONCENTRATE OVER LAKE MICHIGAN
LATE THIS AFTERNOON AND EVENING AS LAKE-EFFECT PARAMETERS
RAPIDLY IMPROVE. THIS SHOULD LEAD TO FOCUSED LAKE-EFFECT
SHOWERS AND POTENTIALLY A FEW THUNDERSTORMS SHIFTING INLAND
FROM SOUTHERN LAKE MICHIGAN INTO NORTHWESTERN INDIANA THIS
EVENING. SCATTERED LAKE EFFECT SHOWERS MAY LINGER AFTER
MIDNIGHT, BUT THEY ARE EXPECTED TO DIMINISH TOWARD SATURDAY
MORNING AS INVERSION HEIGHTS LOWER AND LAKE-EFFECT PARAMETERS
WEAKEN FOLLOWING THE PASSAGE OF THE UPPER-LEVEL TROUGH.
OUTSIDE OF LAKE-EFFECT PRECIPITATION AND CLOUD COVER IN
NORTHWESTERN INDIANA, SKIES WILL CLEAR AND WINDS WILL GRADUALLY
SUBSIDE THIS EVENING. THIS WILL BE ESPECIALLY TRUE ACROSS
INTERIOR PORTIONS OF NORTHERN ILLINOIS, WHERE THE COLDEST
TEMPERATURES OF THE SEASON ARE FORECAST TONIGHT. THE CURRENT
FORECAST REMAINS ON TRACK FOR A COUPLE OF HOURS OF NEAR-FREEZING
TEMPERATURES EARLY SATURDAY MORNING, MOST NOTABLY ACROSS FAR
NORTHERN ILLINOIS FROM THE FOX VALLEY WESTWARD. CONSEQUENTLY, NO
CHANGES WERE MADE TO THE FROST AND FREEZE HEADLINES IN EFFECT
FOR INTERIOR NORTHERN ILLINOIS LATE TONIGHT.
FOLLOWING A CHILLY AND FROSTY START ON SATURDAY, FULL SUNSHINE
AND LIGHT WINDS ARE FORECAST AS THE SURFACE HIGH MOVES DIRECTLY
OVER THE REGION. THE ABUNDANT SUNSHINE WILL HELP TEMPERATURES
REBOUND INTO THE UPPER 50S DURING THE AFTERNOON. ANOTHER CHILLY
NIGHT WILL FOLLOW SATURDAY NIGHT AS TEMPERATURES DROP BACK INTO
THE 30S. GIVEN THE LIGHT WINDS, ADDITIONAL FROSTY CONDITIONS ARE
POSSIBLE, PARTICULARLY EAST OF I-55 WHERE THE LIGHTEST WINDS
ARE EXPECTED. WE WILL CONTINUE TO MONITOR THIS PERIOD FOR
POTENTIAL FROST HEADLINES.
THE COLD SNAP WILL BE SHORT-LIVED AS CONDITIONS TRANSITION BACK
TO A MILD AND DRY AUTUMN PATTERN. HIGH TEMPERATURES ARE
FORECAST TO RETURN TO THE 60S ON SUNDAY AND MONDAY, BEFORE
WARMING INTO THE 70S FOR THE REMAINDER OF NEXT WEEK WITH LITTLE
TO NO CHANCE OF RAIN.
KJB
AVIATION /06Z TAFS THROUGH 12Z SUNDAY/
ISSUED AT 1226 AM CDT SAT OCT 17 2026
KEY AVIATION MESSAGES FOR THE CURRENT TAF PERIOD:
- PERIODS OF LAKE-EFFECT RAIN SHOWERS EXPECTED THROUGH 12Z
OVER NORTHWEST INDIANA
RECENT RADAR IMAGERY SHOWERS A STEADY STREAM OF LAKE-EFFECT
RAIN SHOWERS CONTINUING TO MOVE NORTH TO SOUTH OVER LAKE
MICHIGAN AND INTO NORTHWEST INDIANA. THIS ACTIVITY WILL CONTINUE
TO BRING PERIODS OF RAIN TO KGYY AND REGIONAL TERMINALS NEARBY
THROUGH DAYBREAK. A FEW SHOWERS MAY GET CLOSE TO THE EASTERN
SIDE OF MDW, BUT NO PRECIP IS EXPECTED THERE, JUST FEW/SCT
CLOUDS DUE TO PROXIMITY.
OTHERWISE, QUIETER VFR CONDITIONS ARE EXPECTED THROUGH THE TAF
WINDOW. WINDS CURRENTLY REMAIN OUT OF THE NORTH. THERE ARE A FEW
LINGERING SPOTS THAT FEATURE GUSTS TO 20 KNOTS, BUT THAT SHOULD
CONTINUE TO DIMINISH SHARPLY THROUGH THE OVERNIGHT. WINDS, 5 TO
10 KNOTS, WILL TURN TO THE SOUTHWEST THIS MORNING AND REMAIN
THERE THROUGH TOMORROW NIGHT. SUNDAY IS LOOKING A LITTLE
BREEZIER, BUT CURRENTLY OUTSIDE OF THE CURRENT TAF WINDOW.
DK
MARINE
ISSUED AT 133 PM CDT FRI OCT 16 2026
NORTHERLY GALES TO 40KT ARE FORECAST THIS AFTERNOON AND EVENING,
WITH STRONGEST GUSTS TO 40KT+ LIKELY WITHIN THE LAKE ENHANCED
CONVERGENCE BAND AND WITH MORE ROBUST LAKE EFFECT SHOWERS OVER
THE INDIANA WATERS EAST OF GARY. IN ADDITION TO AN ISOLATED
THUNDERSTORM OR TWO LATE THIS AFTERNOON, CONDITIONS ARE EXPECTED
TO BECOME FAVORABLE FOR WATERSPOUTS LATE THIS AFTERNOON INTO
THIS EVENING. WATERSPOUT RISK IS EXPECTED TO DIMINISH LATE THIS
EVENING AS INVERSION HEIGHTS LOWER. LAKE EFFECT SHOWER INTENSITY
AND COVERAGE WILL DECREASE OVERNIGHT ALSO IN RESPONSE TO THE
DECREASING INVERSION HEIGHTS.
LOT WATCHES/WARNINGS/ADVISORIES
IL...FREEZE WARNING FROM 5 AM TO 8 AM CDT THIS MORNING FOR ILZ003-
ILZ004-ILZ005-ILZ008-ILZ010-ILZ011-ILZ012.
FROST ADVISORY FROM 5 AM TO 8 AM CDT THIS MORNING FOR ILZ006-
ILZ019-ILZ020.
IN...NONE.
LM...GALE WARNING UNTIL 1 AM CDT EARLY THIS MORNING FOR THE IL AND
IN NEARSHORE WATERS.
SMALL CRAFT ADVISORY UNTIL 10 AM CDT THIS MORNING FOR THE IL
NEARSHORE WATERS.
SMALL CRAFT ADVISORY UNTIL 3 PM CDT THIS AFTERNOON FOR THE IN
NEARSHORE WATERS.
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