617
FXUS63 KLOT 252339
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
539 PM CST SUN JAN 25 2026
KEY MESSAGES
- SNOW, FALLING HEAVILY AT TIMES WITH RATES UP TO AROUND AN INCH
PER HOUR, WILL AFFECT AREAS NEAR THE LAKE THROUGH THIS
EVENING. LAKE EFFECT WILL SHIFT EAST FROM IL INTO IN BY EARLY
EVENING AND EAST OF PORTER COUNTY BY AROUND MIDNIGHT.
- SNOW WILL END AWAY FROM LAKE MICHIGAN BY EARLY EVENING.
- DANGEROUSLY COLD WIND CHILLS EXPECTED LATE TONIGHT AND MONDAY
MORNING.
UPDATE
ISSUED AT 527 PM CST SUN JAN 25 2026
HAVE UPGRADED LAKE COUNTY INDIANA TO A WINTER STORM WARNING
THROUGH 8PM. ONGOING HEAVIER LES COMBINED WITH UPSTREAM TRENDS
WITH THE DOMINANT LES BAND OVER WESTERN LAKE MICHIGAN SUGGEST
THAT CONSOLIDATION OF THE LES IS ONGOING INTO A MORE FORMIDABLE
BAND EARLY THIS EVENING. WHILE THIS WAS EXPECTED, TRENDS TOWARD
A LONGER RESIDENCE TIME OF THE BAND (UP TO TWO HOURS), LOCALLY
HIGHER WINDS IN THE HEART OF THE BAND, AND A HIGHLY TRAVELED
CORRIDOR SUPPORT THE UPGRADE TO A WARNING. SNOWFALL RATES IN
THE MAIN BAND WILL LIKELY EXCEED 2"/HR AS MUCH OF THE CONVECTIVE
LAYER AND ASSOCIATED ASCENT RESIDE IN THE DGZ. AREA WEBCAMS
ALSO SHOW THAT EFFICIENT SNOWFLAKE GENERATION IS ONGOING WITH
AGGREGATION ALSO PRESENT.
KLUBER
DISCUSSION
ISSUED AT 232 PM CST SUN JAN 25 2026
BACK EDGE OF THE SYNOPTIC SNOW IS MOVING EAST ACROSS THE AREA
THIS AFTERNOON AND SHOULD CONTINUE EASTWARD WITH SNOW ENDING
FROM EAST TO WEST THROUGH EARLY EVENING. LAKE ENHANCED SNOW
WILL TRANSITION TO PURE LAKE EFFECT SNOW BY EARLY EVENING AS THE
SYNOPTIC SNOWS MOVE OFF TO THE EAST.
RECENT ACARS SOUNDINGS OUT OF MDW DEPICT A SHARP INVERSION
AROUND 5KFT, SO LAKE INDUCED INSTABILITY IS SHALLOW, BUT VERY
STRONG. AIDED BY THE SYNOPTIC SNOWS, THE LAKE ENHANCED SNOW THIS
MORNING HAS BEEN FALLEN HEAVILY AT TIMES WITH SNOWFALL RATES UP
TO AN INCH PER HOUR. LAKE ENHANCED SNOW HAS PENETRATED AS FAR
INLAND AS KANKAKEE COUNTY, THOUGH ANTICIPATE THE INLAND
PENETRATION AND PROBABLY THE INTENSITY OF THE SNOW WILL DECREASE
A BIT AS THE SEEDER-FEEDER PROCESS ENDS AS SYNOPTIC SNOWS SHIFT
EAST.
ANY POTENTIAL DECREASE IN INTENSITY OF THE LAKE EFFECT LOOKS TO
BE SHORT LIVED EARLY THIS EVENING AS MID-UPPER LEVEL TROUGH
APPROACHES THIS EVENING. HEIGHT FALLS IN ADVANCE OF THE TROUGH
ARE PROGGED TO RESULT IN RISING INVERSION HEIGHTS AND DEEPENING
LAKE INDUCED CONVECTIVE LAYER. IN ADDITION TO THE RISING
INVERSION HEIGHT, THE NOCTURNAL STRENGTHENING OF THE LAND BREEZE
CONVERGENCE ZONE SHOULD LEAD TO THE DEVELOPMENT OF AN INTENSE
NARROW BAND OF HEAVY LAKE EFFECT SNOW AS THE FOCUS SHIFTS EAST
INTO PORTER COUNTY.
LAKE EFFECT PARAMETERS ARE FORECAST TO BECOME EXCEPTIONALLY
FAVORABLE FOR A VERY INTENSE LAKE EFFECT SNOW BAND, WITH THE
MAIN QUESTION FOR OUR CWA BEING HOW QUICKLY IT ORGANIZES AND
INTENSIFIES. BY LATE EVENING AND ESPECIALLY AFTER MIDNIGHT, IT
WOULDN'T BE AT ALL SURPRISING TO SEE 2-3"+ PER HOUR SNOWFALL
RATES WITH THE BAND. THE POTENTIAL RAMP UP IN INTENSITY OF THE
LAKE EFFECT BAND LOOKS TO OCCUR FAR ENOUGH WEST TO JUSTIFY THE
EARLIER UPGRADE OF PORTER COUNTY TO A WINTER STORM WARNING AND
BUMPING UP SNOWFALL TOTALS THERE. THE CEILING IS HIGH WITH THIS
EVENT, SHOULD THE BAND INTENSIFY ON THE EARLIER END OF THE
SPECTRUM AND PARTICULARLY IF IT WERE TO SLOW ITS PROGRESSION
ACROSS PORTER COUNTY, THEN DOUBLE DIGIT ADDITIONAL SNOWFALL
TOTALS WOULD BE POSSIBLE. ON THE OTHER END OF THE SPECTRUM, IF
THE BAND WERE TO REMAIN MORE PROGRESSIVE AND THE INTENSITY WERE
TO NOT TAKE OFF UNTIL IT IS EAST OF PORTER COUNTY, THEN THE
ADDITIONAL SNOWFALL AMOUNTS IN NORTHERN PORTER COUNTY COULD END
UP MORE IN THE 2-4" RANGE.
IN THE WAKE OF THE SNOW, SKIES WILL CLEAR OUT AND WITH MANY
AREAS NOW COVERED IN A FRESH BLANKET OF FLUFFY NEW SNOW, WOULD
ANTICIPATE TEMPS TO RESPOND NICELY TO THE COLD AIR ADVECTION.
MADE NO SIGNIFICANT CHANGES TO TEMPS TONIGHT, BUT DID NUDGE HIGH
TEMPS DOWN A BIT FOR MONDAY. NORTHWEST WINDS 10-15 MPH SHOULD
SEND WIND CHILLS DOWN 15 TO 25 BELOW ZERO LATE TONIGHT INTO
MONDAY MORNING, SO COLD WEATHER ADVISORY LOOKS TO BE IN GOOD
SHAPE WITH NO CHANGES PLANNED.
- IZZI
MONDAY NIGHT THROUGH SATURDAY:
ISSUED AT 340 AM CST SUN JAN 25 2026
THE NEXT ROBUST CLIPPER SYSTEM WILL DESCEND OUT OF SASKATCHEWAN
ON MONDAY AND THEN ACROSS THE UPPER GREAT LAKES REGION MONDAY
NIGHT INTO TUESDAY MORNING. SEEING GENERALLY GOOD AGREEMENT ON
THE HANDLING OF THIS FEATURE, WITH GUIDANCE TAKING THE CORE OF
THE MOST ROBUST MID-LEVEL HEIGHT FALLS TO OUR NORTH. THAT SAID,
THE MAGNITUDE OF LARGE SCALE FORCING IS QUITE ROBUST.
WHILE GUIDANCE DOESN'T APPEAR TO FORMALLY PRODUCE SNOW ACCUMS
IN OUR AREA, FORECAST SOUNDINGS FROM VARIOUS GUIDANCE WOULD
SUPPORT FLURRIES OR LIGHT SNOW WITH SATURATION DOWN UNDER
850-900 MB, PARTICULARLY LATE MONDAY NIGHT THROUGH TUESDAY
MORNING ACROSS ROUGHLY THE NORTHEASTERN HALF OF THE CWA AND
ESPECIALLY ACROSS FAR NORTHEAST ILLINOIS. THEREAFTER, STEEPENING
0-1 KM LAPSE RATES IN THE WAKE OF THE ASSOCIATED SURFACE FRONT
LOOK TO DRIVE INCREASING SATURATION INTO THE BASE OF A FAIRLY
DEEP DENDRITIC GROWTH ZONE LATE TUESDAY MORNING AND AFTERNOON.
LOW-LEVEL F-GEN IS GENERALLY TRANSIENT OR NON- EXISTENT,
SUGGESTING THE THREAT FOR BONAFIDE SQUALLS IS LOW, BUT SEEING A
SIGNAL OF NW-SE ORIENTED STREAKS OF QPF IN SOME OF THE GUIDANCE
WHICH IS LIKELY INDICATIVE OF ISOLATED-SCATTERED GUSTY SNOW
SHOWERS THROUGH TUESDAY MORNING AND EARLY AFTERNOON. AT THIS
TIME, HAVE NOT FORMALLY ADDED A SNOW SHOWER MENTION TO THE
GRIDS, BUT IF TRENDS CONTINUE, WILL NEED TO CONSIDER A WEATHER
MENTION DURING THIS TIME FRAME. CAN'T TOTALLY RULE OUT SOME
DISORGANIZED LES MEANDERING INTO FAR NE PORTER COUNTY TUESDAY
AFTERNOON GIVEN SLIGHTLY MORE NW ORIENTED BOUNDARY LAYER FLOW,
BUT THE BULK OF ANY LAKE EFFECT LOOKS TO REMAIN DECIDEDLY TO OUR
EAST.
A REINFORCING SHOT OF COLD AIR WILL SEND LOW TEMPERATURES TUESDAY
NIGHT BACK TO EITHER SIDE OF 0 DEGREES WITH COLDER WIND CHILLS
GIVEN A STEADY WESTERLY BREEZE.
THE NEXT ROBUST DISTURBANCE ARRIVES LATE TUESDAY NIGHT INTO
WEDNESDAY. GUIDANCE APPEARS TO BE SETTLING IN ON A SLIGHTLY
FARTHER SOUTH TRACK AT THIS POINT, ALTHOUGH THERE'S GENERALLY
LOW CONFIDENCE THIS FAR OUT WITH THESE TYPES OF SYSTEMS. WILL BE
A PERIOD TO WATCH AS THIS WOULD BE ANOTHER INSTANCE OF LIGHT
SNOW ACCUMULATIONS FALLING INTO A VERY COLD AIRMASS WHERE ROAD
TREATMENTS WOULD LIKELY BE MOSTLY INEFFECTIVE. STRONGEST SIGNAL
FOR LIGHT SNOW ACCUMULATIONS INTO WEDNESDAY AFTERNOON ARE
ROUGHLY SOUTH (TO WELL SOUTH) OF I-80.
LOTS OF SPREAD IN THE HANDLING OF THE GENERAL LARGE SCALE
SYNOPTIC PATTERN BY THE END OF THE WEEK. STILL SEEING A SIGNAL
(EPHEMERAL AS IT MAY BE FROM RUN-TO-RUN) OF A POTENTIALLY
INTERESTING SET UP TOWARDS THURSDAY NIGHT - FRIDAY INVOLVING AN
INTENSE SHORTWAVE TROUGH PUSHING SOUTHWESTWARD ACROSS THE GREAT
LAKES WHICH WOULD TURN THE LAKE EFFECT SNOW MACHINE BACK ON IN
THE GENERAL REGION.
OTHERWISE, CONTINUED COLD IS THE MESSAGE THROUGH NEXT WEEK.
COULD BE SOME PERIODS WHERE WE'RE FLIRTING WITH COLD WEATHER
HEADLINE CRITERIA AT TIMES, BUT NOTHING TO THE LEVEL OF WHAT WE
EXPERIENCED THIS PAST FRIDAY/SATURDAY.
CARLAW
AVIATION /00Z TAFS THROUGH 06Z TUESDAY/
ISSUED AT 538 PM CST SUN JAN 25 2026
THE LAKE EFFECT SNOW WILL CONTINUE TO PUSH EASTWARD WITH TIME
THIS EVENING, ENDING AT GYY WITHIN THE NEXT FEW HOURS.
OTHERWISE, A FLURRY OR TWO MAY FALL THROUGH THE OVERNIGHT HOURS
AS A STRATUS DECK MEANDERS THROUGH THE REGION. BASED ON THE
CURRENT BACK EDGE OF THE STRATUS OVER SOUTHEASTERN WISCONSIN,
WOULD EXPECT CLEARING TO TAKE PLACE SOMETIME BEFORE DAYBREAK
MONDAY IN LINE WITH THE PASSAGE OF THE CYCLONIC SHEAR AXIS OF
THE DEPARTING UPPER-LEVEL TROUGH. WINDS WILL REMAIN
NORTHWESTERLY THROUGH THE NIGHT.
THERE MAY BE AN OPPORTUNITY FOR CLEAR SKIES DURING DAYLIGHT
HOURS TOMORROW AS WINDS GRADUALLY BACK WESTERLY AND EVENTUALLY
SOUTHWESTERLY THROUGH THE AFTERNOON. UPPER-LEVEL CLOUDS WILL
THICKEN DURING THE EVENING IN ADVANCE OF A CLIPPER SYSTEM
TRACKING THROUGH THE UPPER GREAT LAKES. IN FACT, A PERIOD OF
LLWS MAY MATERIALIZE TOMORROW NIGHT AS FLOW AT 2000 FEET
INCREASES TO 50-55KT.
BORCHARDT
HYDROLOGY
ISSUED AT 230 PM CST FRI JAN 23 2026
RIVER GAUGES, REPORTS FROM LOCAL OFFICIALS, AND REPORTS FROM
TRAINED ICE SPOTTERS CONTINUE TO INDICATE A FEW ICE JAMS ACROSS
THE AREA DUE TO THE SIGNIFICANT INCREASE IN RIVER ICE OVER
RECENT DAYS. WITH CONTINUED COLD WEATHER INTO NEXT WEEK,
CONDITIONS WILL REMAIN FAVORABLE FOR RIVER ICE FORMATION. WHILE
NO WIDESPREAD FLOODING IS EXPECTED, LOCALIZED ICE JAMS MAY
OCCUR.
- NWS CHICAGO
LOT WATCHES/WARNINGS/ADVISORIES
IL...COLD WEATHER ADVISORY FROM MIDNIGHT TONIGHT TO NOON CST MONDAY
FOR ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-ILZ010-ILZ011-
ILZ012-ILZ013-ILZ019-ILZ020-ILZ021-ILZ023-ILZ032-ILZ033-
ILZ039-ILZ103-ILZ104-ILZ105-ILZ106-ILZ107-ILZ108.
WINTER STORM WARNING UNTIL 6 PM CST THIS EVENING FOR ILZ104-
ILZ105.
WINTER WEATHER ADVISORY UNTIL 6 PM CST THIS EVENING FOR ILZ023-
ILZ108.
IN...COLD WEATHER ADVISORY FROM MIDNIGHT CST /1 AM EST/ TONIGHT TO
NOON CST /1 PM EST/ MONDAY FOR INZ001-INZ002-INZ010-
INZ011-INZ019.
WINTER STORM WARNING UNTIL 8 PM CST THIS EVENING FOR INZ001.
WINTER STORM WARNING UNTIL MIDNIGHT CST TONIGHT FOR INZ002.
WINTER WEATHER ADVISORY UNTIL 9 PM CST /10 PM EST/ THIS
EVENING FOR INZ010-INZ011-INZ019.
LM...SMALL CRAFT ADVISORY UNTIL 6 PM CST TUESDAY FOR THE IL AND IN
NEARSHORE WATERS.
VISIT US AT WEATHER.GOV/CHICAGO
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page