103
FXUS63 KLOT 261136
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
536 AM CST FRI DEC 26 2025
KEY MESSAGES
- SOME LIGHT RAIN, DRIZZLE, AND FOG ARE EXPECTED THIS MORNING,
LOCALLY DENSE FOG POSSIBLE.
- SHOWERS DEVELOP SATURDAY NIGHT AND CONTINUE SUNDAY.
- THERE IS A CHANCE OF THUNDERSTORMS, POSSIBLY SEVERE, SOUTH OF
I-80 SUNDAY AFTERNOON/EVENING.
- VERY WINDY AND MUCH COLDER MONDAY WITH SOME SNOW SHOWERS
POSSIBLE IN THE MORNING.
UPDATE
ISSUED AT 530 AM CST FRI DEC 26 2025
HAVE OPTED TO ISSUE A DENSE FOG ADVISORY FOR ABOUT THE SOUTHWEST
HALF OR SO OF OUR CWA. EVEN THOUGH THE DENSE FOG THREAT THIS
MORNING IS MORE TRANSIENT THAN IS TYPICAL, STILL FEEL IT
WARRANTS AN ADVISORY GIVEN COUPLE/FEW HOUR DURATION OF DENSE FOG
IN MOST AREAS.
THERE IS AN AXIS OF DENSE FOG AHEAD OF A NORTHWARD ADVANCING
WARM FRONT FROM AROUND VYS TO PNT TO DNV. AS THE WARM FRONT
PASSES, LOOK FOR VISIBILITIES TO QUICKLY IMPROVE SOUTH OF
HIGHWAY 24 EARLY THIS MORNING. FARTHER NORTH, THERE IS A
LARGER EASTWARD ADVANCING AREA OF DENSE FOG IN THE VICINITY OF
THE CENTER OF THE APPROACHING LOW PRESSURE OVER IA AND NW IL.
WHILE NOT EVERYONE IN THE ADVISORY AREA WILL BE SOCKED IN THE
ENTIRE DURATION OF THE ADVISORY, GIVEN THE 2 APPROACHING AREAS
OF DENSE FOG, FELT CONFIDENCE IS FAIRLY HIGH IN A PERIOD OF
1/4SM OR LESS VSBY EARLY THIS MORNING WITHIN THE ADVISORY AREA.
SOUTHERN PORTIONS OF THE ADVISORY MAY BE ABLE TO BE CANCELLED A
BIT EARLY AS WARM FRONT ADVANCES NORTH. ALSO, THERE IS A
REASONABLY HIGH CHANCE THAT DENSE FOG COULD SPREAD EAST OF THE
CURRENT ADVISORY IN THE NEXT COUPLE OF HOURS, NECESSITATING AN
EASTWARD EXPANSION OF THE ADVISORY. OPTED TO HOLD OFF FOR NOW
AND WILL MONITOR TRENDS, BUT THERE'S A PRETTY GOOD CHANCE THAT
THE ADVISORY WILL NEED TO BE EXPANDED EAST AND PERHAPS RUN AN
HOUR OR SO LONGER.
- IZZI
DISCUSSION
ISSUED AT 248 AM CST FRI DEC 26 2025
LOW PRESSURE WILL TRACK ACROSS NORTHERN IL THIS MORNING,
REACHING SOUTHERN LAKE MICHIGAN LATER THIS MORNING. DRIZZLY,
SHOWERY CONDITIONS ARE EXPECTED IN ADVANCE OF THE LOW,
ESPECIALLY NORTH OF I-80 THROUGH THE EARLY MORNING HOURS. FOGGY
CONDITIONS ARE EXPECTED THIS MORNING, WITH LOCALLY DENSE FOG A
PRETTY GOOD BET, ESPECIALLY NORTH OF I-80 CLOSER TO THE TRACK OF
THE SFC LOW. SHOWERS ARE EXPECTED TO END AND FOG DISSIPATE LATE
THIS MORNING AS NORTHWEST WINDS USHER IN SLIGHTLY LOWER SURFACE
DEWPOINTS IN THE WAKE OF THE LOW.
WHILE SOME SLIGHT DRYING OF THE NEAR SURFACE LAYER IS EXPECTED
TODAY, A SHARP FRONTAL INVERSION SEEMS LIKELY TO LOCK IN A
STRATUS DECK OVER THE AREA THROUGH SATURDAY. THE STRATUS WILL
LIKELY SIGNIFICANTLY LIMIT THE DIURNAL TEMP SWING TONIGHT INTO
SATURDAY AND HAVE BUMPED UP LOW TEMPS TONIGHT AND LOWERED HIGH
TEMPS SATURDAY. WILL NEED TO WATCH FOR STRATUS BUILDING DOWN
INTO FOG TONIGHT GIVEN THE LIGHT WINDS AND STILL CHILLY SOIL
TEMPS.
A STRONG UPPER TROUGH WILL DIG SOUTHEAST INTO THE NORTHERN
PLAINS SATURDAY NIGHT RESULTING IN CYCLOGENESIS OVER THE LOWER
MISSOURI VALLEY. STRENGTHENING SOUTHERLY LOW LEVEL JET WILL
RAPIDLY DRIVE AN UNSEASONABLY MOIST AND MILD AIR MASS NORTHWARD
INTO THE MID-MISSISSIPPI VALLEY AND LOWER GREAT LAKES. SHOWERS
WILL LIKELY BREAK OUT ACROSS THE AREA SATURDAY NIGHT IN
ASSOCIATION WITH THIS STRONG LOW LEVEL THETA-E ADVECTION. CAN'T
TOTALLY RULE OUT AN ISOLATED THUNDERSTORM OR TWO LATER SATURDAY
NIGHT, BUT OPTED TO KEEP THUNDER OUT OF THE GRIDS FOR NOW.
GFS AND ECMWF ALONG WITH THEIR RESPECTIVE ENSEMBLE SUITES ARE IN
GOOD AGREEMENT ON A SURFACE LOW OVER NORTHEAST MO OR NORTHWEST
IL SUNDAY MORNING AND EXPLOSIVELY DEEPENING IT AS IT TRACKS
NORTHEASTWARD TO AROUND LAKE HURON BY EARLY MONDAY MORNING. GFS
AND ECMWF BOTH BRING NEAR 60 DEGREE DEWPOINTS NORTH INTO OUR
SOUTHEASTERN CWA SUNDAY AFTERNOON. WHILE WEAK LOW AND MID LEVEL
LAPSE RATES SHOULD HELP LIMIT INSTABILITY, SOME WEAK BOUNDARY
LAYER DESTABILIZATION IS STILL LIKELY WITH SFC TDS UP AROUND
60F. GIVEN THE STRONG FORCING AND SEASONABLY STRONG WIND FIELDS,
QUITE PLAUSIBLE THAT THERE COULD BE A STRONG FORCED LINE OF LOW
TOPPED CONVECTION (POSSIBLY LACKING LIGHTNING) THAT COULD POSE A
THREAT OF DAMAGING WINDS INTO OUR SOUTHERN/SOUTHEASTERN CWA
SUNDAY AFTERNOON. IF THERE WERE TO BE ANY UNEXPECTED PARTIAL
CLEARING IN THE WARM SECTOR SUNDAY AFTERNOON, THEN SLIGHTLY
BETTER BL DESTABILIZATION COULD EVEN RESULT IN SOME QLCS
MESOVORTEX FUNNY BUSINESS GIVEN THE VERY STRONG 0-1KM SHEAR.
VERY STRONG COLD AIR ADVECTION IS EXPECTED SUNDAY NIGHT WITH
925MB AND 850MB TEMPS BOTH PROGGED TO DROP 20C+ IN JUST 12
HOURS. BY 12Z MONDAY, GFS AND ECMWF BOTH HAVE THIS SFC LOW DOWN
TO SUB-980MB WITH A VERY LARGE AND STRONG WIND FIELD ASSOCIATED
WITH THIS CYCLONE. STRONG COLD AIR ADVECTION SHOULD KEEP
BOUNDARY LAYER WELL MIXED SUNDAY NIGHT INTO MONDAY WHICH COULD
ALLOW FOR SOME 40+ MPH GUSTS.
BOTH GFS AND ECMWF HAVE A SUBTLE SHORTWAVE PIVOTING AROUND THE
SOUTHWESTERN FLANK OF THIS EXPLOSIVELY DEEPENING CYCLONE, WHICH
COULD EASY RESULT IN SOME SNOW SHOWERS OR FLURRIES MONDAY
MORNING, ESPECIALLY NORTHERN CWA AS IT LOOKS NOW.
WHILE THE WIND ON MONDAY WILL MAKE IT FEEL COLDER, THE ACTUAL
AIR MASS DOESN'T LOOK TO BE PARTICULARLY ANOMALOUS FOR LATE
DECEMBER. HOWEVER, THE CONTRAST TO THE VERY MILD AND
UNSEASONABLY "HUMID" AIR MASS SATURDAY, WILL STILL MAKE THE COLD
FEEL PRETTY BITING MONDAY. FAIRLY SEASONABLE TO SLIGHTLY BELOW
AVERAGE TEMPERATURES ARE EXPECTED TO CLOSE OUT 2025, BUT TEMPS
LOOK TO TREND MORE SOLIDLY BELOW AVERAGE TO START 2026. AS OUR
POWERFUL WEEKEND CYCLONE PIVOTS CYCLONICALLY NORTHWARD ACROSS
QUEBEC AND TOWARD HUDSON BAY EARLY NEXT WEEK, IT LOOKS LIKE IT
COULD DISLODGE ANOTHER LOBE OF COLD AIR FROM THE NORTHERN
CANADA AND SEND IT SOUTHWARD INTO THE GREAT LAKES. THIS
SECONDARY COLD SHOT LOOKS TO ARRIVE AROUND THE 1ST OF JAN AND
SHOULD KEEP TEMPS BELOW AVERAGE THROUGH THE END OF NEXT WEEK.
WHILE THE PATTERN WILL TURN DECIDEDLY COLDER NEXT WEEK, WE'RE
NOT SEEING ANY STRONG SIGNAL FOR ACCUMULATING SNOW AT THIS TIME.
GIVEN OUR LOCATION IN RATHER CLOSE PROXIMITY TO THE POLAR FRONT
JET, WE'LL NEED TO WATCH FOR ANY LOWER AMPLITUDE NORTHWEST FLOW
CLIPPER LIKE SYSTEMS THAT CAN BE HARD TO PREDICT THIS FAR IN
ADVANCE. GIVEN THE MUTED SIGNAL FOR PRECIP IN THE EPS AND GEFS,
SAW NO NEED TO ADJUST THE NBM WHICH OFFERS UP NO MEANINGFUL
CHANCES FOR SNOW NEXT WEEK.
- IZZI
AVIATION /12Z TAFS THROUGH 18Z SATURDAY/
ISSUED AT 536 AM CST FRI DEC 26 2025
KEY AVIATION MESSAGES FOR THE CURRENT TAF PERIOD:
- LOW VIS/CIGS IS EXPECTED AT TERMINALS WITH LIFR/VLIFR
CONDITIONS THIS MORNING DUE TO FOG/DRIZZLE
- SLOW IMPROVEMENT IN CIGS TO IFR AND EVENTUALLY LOW MVFR
LEVELS THIS AFTERNOON
- POTENTIAL REDEVELOPMENT OF IFR TONIGHT
- LOW CONFIDENCE IN EXACT TIMING OF WINDS SWITCHING TO THE
NORTHWEST
HALF MILE VISIBILITY OR LESS IS CURRENTLY OVER THE MISSISSIPPI
RIVER VALLEY AND GRADUALLY MOVING EASTWARD. FOG/DRIZZLE IS
EXPECTED TO CONTINUE EASTWARD THIS MORNING THROUGH THE CHICAGO
METRO, THOUGH THERE IS SLIGHTLY LOWER CONFIDENCE IN THE EXACT
TIMING OF IMPACTING TERMINALS. WINDS WILL BE OUT OF THE
SOUTHEAST TO START BEFORE SWITCHING TO THE SOUTHWEST BRIEFLY AS
THE VIS TANKS.
ALL THIS VIS REDUCTION IS HAPPENING AHEAD OF AN AREA OF LOW
PRESSURE THAT IS SLOWLY MOVING EAST. AS IT MOVES EAST OF CHICAGO
AFTER 15Z, WINDS WILL SWITCH TO THE NORTHWEST AND PICK UP TO 10
TO 15 KNOTS. THERE IS LOWER CONFIDENCE IN THE EXACT TIMING ON
IMPROVEMENT IN VISIBILITY, BUT VIS SHOULD IMPROVE SOMEWHAT
QUICKLY LATE MORNING IN CONJUNCTION WITH THE WIND SHIFT. WHILE
CIGS WILL LIFT, THEY WILL IMPROVE TO IFR INITIALLY, BEFORE
BECOMING LOW MVFR THIS AFTERNOON.
WINDS WILL ONCE AGAIN BECOME LIGHT THIS EVENING. THERE IS
ANOTHER CHANCE FOR IFR CONDITIONS TO DEVELOP LATE TONIGHT ALONG
WITH SOME FOG. HOWEVER, THERE IS HIGHER CONFIDENCE IN THIS
DEVELOPMENT FOR AREAS WEST OF THE CHICAGO METRO.
DK
LOT WATCHES/WARNINGS/ADVISORIES
IL...DENSE FOG ADVISORY UNTIL 9 AM CST THIS MORNING FOR ILZ003-
ILZ004-ILZ008-ILZ010-ILZ011-ILZ012-ILZ019-ILZ020-ILZ021-
ILZ023-ILZ032-ILZ033-ILZ039-ILZ106-ILZ107-ILZ108.
IN...DENSE FOG ADVISORY UNTIL 9 AM CST /10 AM EST/ THIS MORNING FOR
INZ010-INZ011-INZ019.
LM...SMALL CRAFT ADVISORY UNTIL 9 AM CST THIS MORNING FOR WINTHROP
HARBOR TO NORTHERLY IS. IL.
SMALL CRAFT ADVISORY UNTIL 6 AM CST EARLY THIS MORNING FOR
NORTHERLY IS. IL TO MICHIGAN CITY IN.
VISIT US AT WEATHER.GOV/CHICAGO
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page