971
FXUS63 KLOT 161734
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
1234 PM CDT FRI OCT 16 2026
KEY MESSAGES
- WINDY AND SEASONABLY CHILLY CONDITIONS EXPECTED TODAY WITH
SOME SCATTERED SHOWERS, WIND GUSTS OVER 30 MPH ARE EXPECTED
THIS AFTERNOON.
- EAST OF GARY, LAKE ENHANCED SHOWERS THIS AFTERNOON WILL
TRANSITION TO LAKE EFFECT SHOWERS TONIGHT WITH A SLIGHT CHANCE
OF A THUNDERSTORM NEAR THE SHORE LATE THIS AFTERNOON/EARLY
THIS EVENING. WIND GUSTS TO 45 MPH POSSIBLE NEAR THE NORTHWEST
INDIANA LAKEFRONT THIS AFTERNOON/EARLY EVENING.
- COLDEST NIGHT OF THE SEASON EXPECTED TONIGHT WITH LOWS
NEAR/JUST BELOW FREEZING ACROSS INTERIOR PORTIONS OF NORTHERN
IL.
DISCUSSION
ISSUED AT 315 AM CDT FRI OCT 16 2026
VIGOROUS UPPER TROUGH EVIDENT ON WATER VAPOR IMAGERY EARLY THIS
MORNING MOVING INTO THE UPPER MISSISSIPPI VALLEY. THE ASSOCIATED
SURFACE COLD FRONT HAS NOW PUSHED EAST OF THE CWA WITH GUSTY
NORTHWESTERLY WINDS USHERING IN A COLDER AND LESS HUMID AIR MASS.
SHOWERS ASSOCIATED WITH THE COLD FRONT WILL MOVE EAST OF OUR CWA
WELL BEFORE SUNRISE, HOWEVER ADDITIONAL SCATTERED SHOWERS ARE
EXPECTED THIS AFTERNOON IN ASSOCIATION WITH THE MID-UPPER LEVEL
TROUGH MOVING ACROSS THE AREA. DESPITE THE DRIER LOW LEVEL AIR MASS
ADVECTING IN, A POCKET OF VERY COLD AIR ALOFT ASSOCIATED WITH THE
TROUGH (-27C AT 500MB ON 00Z BISMARK SOUNDING) WILL AID IN
DESTABILIZATION AND SUPPORT SCATTERED SHOWERS THIS AFTERNOON. WHILE
SCATTERED SHOWERS ARE EXPECTED AREA WIDE LATE THIS MORNING INTO THIS
AFTERNOON, THE ARRIVAL OF THE COLD AIR ALOFT SHOULD RESULT IN A
SIGNIFICANT INCREASE IN LAKE INDUCED INSTABILITY RESULTING IN MORE
WIDESPREAD AND ROBUST SHOWERS OVER LAKE MICHIGAN SPREADING INTO
NORTHWEST INDIANA (MAINLY EAST OF GARY). FORECAST SOUNDINGS DEPICT
THE TOP OF THE MOIST CONVECTIVE LAYER REACHING ABOVE THE -20C LEVEL
THIS AFTERNOON OVER SOUTHERN LAKE MICHIGAN, WHICH COULD EVEN ALLOW
AN ISOLATED THUNDERSTORM OR TWO.
THE CLOUD COVER, SCATTERED SHOWERS, AND STRONG COLD AIR ADVECTION
SHOULD RESULT IN VERY LITTLE DIURNAL RECOVERY IN TEMPERATURES WITH
TEMPERATURES HOLDING NEARLY STEADY IN THE UPPER 40S TO MID 50S.
STRONG AND GUSTY NORTHWEST WINDS WILL ONLY ADD TO THE CHILL WITH
GUSTS OVER 30 MPH LIKELY TODAY. LAKE INDUCED INSTABILITY AND LESS
FRICTION WILL RESULT IN EVEN STRONGER WINDS OVER LAKE MICHIGAN
BLEEDING ONTO THE NORTHWEST INDIANA SHORE THIS AFTERNOON INTO EARLY
THIS EVENING WHEN A FEW GUSTS TO AROUND 45 MPH ARE EXPECTED.
SKIES CLEAR OUT EARLY THIS EVENING AND WINDS WILL GRADUALLY SUBSIDE
TONIGHT, THE EXCEPTION BEING INTO NORTHWEST INDIANA WHERE LAKE
EFFECT SHOWERS WILL LIKELY CONTINUE. THE LAKE CLOUDINESS AND SHOWERS
WILL KEEP TEMPS RELATIVELY MILDER OVER NORTHWEST INDIANA, BUT ELSE
LOOK FOR THE COLDEST NIGHT THUS FAR THIS AUTUMN. HAVE UPGRADED THE
FREEZE WATCH TO A FREEZE WARNING AND EXPANDED IT A BIT FARTHER SOUTH
AND EAST. HAVE BUFFERED THE FREEZE WARNING WITH A FROST ADVISORY FOR
A COUPLE OF COUNTIES, THOUGH ADMITTEDLY, TONIGHT DOESN'T LOOK
PARTICULARLY FAVORABLE FOR FROST. WINDS WILL BE SLOW TO SUBSIDE,
THOUGH OVER OUR WESTERN CWA VERY LATE TONIGHT WE COULD SEE WINDS GET
CLOSE TO DECOUPLING. THE WINDS SHOULD PREVENT STRONG RADIATIONAL
COOLING AND WITH T/TD SPREADS EXPECTED TO REMAIN AT OR ABOVE 5F,
FROST POTENTIAL IS PRETTY IFFY TONIGHT. NONETHELESS, WITH TEMPS
PROGGED TO GET CLOSE TO FREEZING AND WINDS SUBSIDING TOWARD SUNRISE,
FELT IT WAS PRUDENT TO HOIST A FROST ADVISORY OUT OF AN ABUNDANCE OF
CAUTION AND AS A HEDGE IN CASE TEMPS WERE TO GET COLDER AND DIP TO
OR JUST BELOW FREEZING.
AS THE SHARP UPPER TROUGH SHIFTS EAST OF THE REGION LATER TONIGHT,
INVERSION HEIGHTS WILL COME CRASHING DOWN AND SHOULD SHUT DOWN THE
LAKE EFFECT SHOWERS BY OR JUST SHORTLY AFTER SUNRISE SATURDAY.
OUTSIDE OF THE DECREASING LAKE EFFECT CLOUDINESS DOWNWIND OF THE
LAKE SAT AM, LOOK FOR SUNNY SKIES THIS WEEKEND. LIGHT WINDS WITH THE
STILL CHILLY AIR MASS IN PLACE SHOULD RESULT IN BELOW AVERAGE TEMPS
IN THE 50S FOR HIGHS SATURDAY. SATURDAY NIGHT THE FROST/FREEZE
POTENTIAL LOOKS GREATEST AWAY FROM THE IMMEDIATE LAKESHORE IN
NORTHWEST INDIANA WHERE STRONG RADIATIONAL COOLING IS EXPECTED.
FROST/FREEZE HEADLINES WILL LIKELY BE NEEDED SATURDAY NIGHT FOR AT
LEAST PORTIONS OF NORTHWEST INDIANA AND PERHAPS WEST INTO PORTIONS
OF NORTHERN IL AS WELL.
OUR IMPENDING COLD SNAP LOOKS TO BE SHORT LIVED WITH WARM AIR
ADVECTION RAMPING UP SUNDAY AND HIGHS REBOUNDING BACK INTO THE 60S.
UNSEASONABLY MILD WEATHER IS EXPECTED NEXT WEEK WITH HIGHS
APPROACHING 70 MONDAY AND LIKELY IN THE 70S THE REST OF THE WEEK.
AVERAGE HIGHS NEXT WEEK DROP INTO THE UPPER 50S, SO WE'LL BE LOOKING
AT HIGH TEMPS 10 TO NEARLY 20F ABOVE AVERAGE BY THE MIDDLE AND END
OF NEXT WEEK. AFTER THE SHOWER THREAT ENDS OVER MOST OF THE AREA
LATE THIS AFTERNOON AND DOWNWIND OF THE LAKE BY EARLY SATURDAY, NO
PRECIPITATION IS EXPECTED THROUGH THE REST OF THE WEEKEND AND NEXT
WEEK LOOKS DRY AS WELL.
- IZZI
AVIATION /18Z TAFS THROUGH 00Z SUNDAY/
ISSUED AT 1234 PM CDT FRI OCT 16 2026
KEY CONCERNS FOR THE 18Z TAF PERIOD:
* SCATTERED LIGHT SHOWERS THIS AFTERNOON
* MVFR CIGS OVER CHICAGOLAND RETURNING TO VFR THIS AFTERNOON
* AT GYY, PERIODS OF LAKE-EFFECT RAIN EXPECTED LATE THIS
AFTERNOON AND AGAIN LATE TONIGHT INTO EARLY SATURDAY
SCATTERED COVERAGE OF LIGHT RAIN IS DROPPING INTO NORTHERN IL
FROM THE NORTH EARLY THIS AFTERNOON. PERIODS OF LIGHT RAIN WILL
BE POSSIBLE THROUGH THE REST OF THE AFTERNOON. MVFR CIGS OVER
THE REGION HAVE RECENTLY SCATTERED OUT OVER RFD WITH MORE VFR
FOUND UPSTREAM. CHICAGOLAND SITES ARE EXPECTED TO RETURN TO VFR
BY MID- AFTERNOON.
AT GYY, A BAND OF LAKE-EFFECT RAIN SHOWERS WILL TARGET FAR
NORTHWEST IN LATE THIS AFTERNOON INTO EARLY EVENING. PERIODS OF
LIGHT TO MODERATE RAIN WITH MVFR VSBY REDUCTIONS ARE
ANTICIPATED. A SECOND PUSH IS EXPECTED AFTER MIDNIGHT AND MAY
LAST INTO EARLY SATURDAY.
MEANWHILE, NW WINDS WILL TREND TOWARD NNW THROUGH THE AFTERNOON
WHILE REGULAR GUSTS ARE EXPECTED TO GET UP TO NEAR 30 KT FOR
THE MIDDLE AND LATE AFTERNOON. NNW WINDS WILL REMAIN GUSTY
THROUGH MUCH OF THE NIGHT BEFORE EASING FOR SATURDAY.
DOOM
MARINE
ISSUED AT 315 AM CDT FRI OCT 16 2026
WEST TO NORTHWEST WINDS TO 30KT THIS MORNING WILL VEER MORE
NORTHERLY AND INCREASE TO GALES TO 40KT THIS AFTERNOON. NORTHERLY
GALES WILL CONTINUE THIS 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 SATURDAY FOR ILZ003-
ILZ004-ILZ005-ILZ008-ILZ010-ILZ011-ILZ012.
FROST ADVISORY FROM 5 AM TO 8 AM CDT SATURDAY FOR ILZ006-
ILZ019-ILZ020.
IN...WIND ADVISORY UNTIL 10 PM CDT THIS EVENING FOR INZ002.
LM...SMALL CRAFT ADVISORY UNTIL 1 PM CDT THIS AFTERNOON FOR THE IL
AND IN NEARSHORE WATERS.
GALE WARNING UNTIL 1 AM CDT SATURDAY FOR THE IL AND IN
NEARSHORE WATERS.
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