504
FXUS63 KLOT 172057
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
257 PM CST SAT JAN 17 2026
KEY MESSAGES
- A PERIOD OF LIGHT SNOW WITH ACCUMULATIONS UP TO AROUND ONE
HALF INCH THROUGH MAY RESULT IN LOCALLY SLIPPERY TRAVEL
THROUGH MID-EVENING.
- ACCUMULATING SNOW IS EXPECTED SUNDAY AFTERNOON INTO THE
EVENING, WITH SLIPPERY TRAVEL CONDITIONS EXPECTED. STRONG WEST
TO NORTHWEST WINDS WITH GUSTS TO 40 MPH WITH AN COLD FRONT
WILL FOLLOW SHORTLY BEHIND THE SNOW.
- BITTERLY COLD CONDITIONS ARE EXPECTED SUNDAY NIGHT THROUGH
TUESDAY MORNING WITH WIND CHILLS 15 BELOW TO 25 BELOW ZERO
POSSIBLE MONDAY MORNING.
DISCUSSION
ISSUED AT 257 PM CST SAT JAN 17 2026
AN INCREASINGLY SHEARED MID-LEVEL TROUGH AXIS ABOVE A
SHARPENING LOW- LEVEL BAROCLINIC ZONE HAS BEEN ABLE TO WRING OUT
STEADY SNOW ACROSS SOUTHERN WISCONSIN THROUGH THE DAY. THE
RESULTANT AXIS OF LIGHT SNOW WITH EMBEDDED TRANSIENT BANDS OF
HEAVIER SNOW HAS SHIFTED INTO THE NORTHERN TIER OF COUNTIES AS
THE ENTIRE AIRMASS PIVOTS SOUTHEAST. WHERE THE SYNOPTIC SNOW IS
OCCURRING, IMPACTS HAVE BEEN FAIRLY LOW PER RECENT TRAVEL
WEBCAMS. THE BAND OF LIGHT SNOW SHOULD CONTINUE ITS
SOUTHEASTWARD TREK ACROSS NORTHERN ILLINOIS THROUGH MID-EVENING
BEFORE THE REMAINING FORCING FROM THE TROUGH AND ACCELERATING
BAROCLINIC/F-GEN AXIS WEAKEN AND EXIT THE AREA BY LATE EVENING.
WITH THE LOSS OF DAYTIME HEATING AND TEMPS REMAINING STEADY IN
THE MID TEENS, SLIPPERY CONDITIONS ARE EXPECTED TO DEVELOP FOR
AREAS NORTH OF I-80. TOTAL ACCUMULATIONS AROUND A HALF INCH ARE
POSSIBLE, WITH LOCALIZED SWATHS OF AROUND AN INCH NORTH OF I-88.
MEANWHILE AHEAD OF THE MAIN BAND OF SNOW THIS AFTERNOON AND
EARLY EVENING, SCATTERED LIGHT SNOW SHOWERS HAVE BEEN COMMON
WITH DIURNAL SUPPORT. DRY LOW-LEVELS HAVE LIMITED PRECIP AT THE
SURFACE, WITH STRATOCUMULUS BASES GENERALLY 3-4KFT.
BEHIND THE EXITING SYNOPTIC SNOW THIS EVENING, SHALLOW STRATUS
FIRMLY IN THE DGZ SHOULD PERSIST THROUGH MUCH OF THE NIGHT WHILE
PRODUCING ON AND OFF FLURRIES.
PARTLY TO MOSTLY CLOUDY SKIES ARE EXPECTED SUNDAY MORNING AS
MODEST LOW-LEVEL WAA ENSUES. A LOW-AMPLITUDE TROUGH CURRENTLY
OVER NORTHERN ALBERTA WILL STRENGTHEN WHILE TRACKING TOWARD THE
WESTERN GREAT LAKES THROUGH SUNDAY. NOTABLE MID-LEVEL DIFFLUENCE
SOMEWHAT COLLOCATED WITH THE LEFT-EXIT OF A 120 KNOT UPPER-JET
WILL PROVIDE AMPLE ASCENT FOR PRECIP GENERATION OVER THE AREA
MID-AFTERNOON THROUGH MID-EVENING. FULL TOP-DOWN SATURATION WILL
BE THE PRIMARY LIMITING FACTOR FOR A MORE APPRECIABLE SNOW
EVENT, WITH QUESTIONS HOW MUCH OF THE ROBUST SNOW ALOFT REACHES
THE SURFACE. LATEST GUIDANCE SUPPORTS TOTALS AROUND AN INCH OVER
NORTHERN ILLINOIS AND NORTHWEST INDIANA, THOUGH GIVEN THE
FORCING NOTED ABOVE, WOULD NOT BE SURPRISED TO SEE THE SYSTEM
OVERPERFORM WITH HIGHER TOTALS IF SATURATION IS PREVALENT.
AN ARCTIC COLD FRONT WILL QUICKLY CROSS THE AREA SUNDAY
EVENING, USHERING IN RAPIDLY FALLING TEMPS WITH WNW/NW GUSTS TO
40-45MPH. SOME GUSTY SNOW SHOWERS WILL ALSO BE POSSIBLE WITH THE
FRONT. BY DAYBREAK MONDAY, THE COMBINATION OF TEMPS AROUND OR
SLIGHTLY ABOVE ZERO COMBINED WITH THE STRONG WINDS WILL RESULT
IN WIND CHILL READINGS RANGING FROM -15 TO -25, LOWEST WEST OF
THE FOX RIVER VALLEY WHERE A COLD WEATHER ADVISORY MAY BE
NEEDED. HIGHS MONDAY WILL STRUGGLE TO REACH 10 DEGREES, WITH
MAXIMUM WIND CHILLS REMAINING SOLIDLY BELOW ZERO. WINDS WILL
BEGIN TO DIMINISH MONDAY NIGHT AS A SURFACE HIGH PASSES SOUTH OF
THE AREA, BUT WIND CHILLS AS LOW AS -15 DEGREES CAN BE EXPECTED
TUESDAY MORNING.
KLUBER
RATHER GOOD CONSISTENCY IN THE MODELS AND THEIR ENSEMBLES FOR A
BRIEF MODERATION OF TEMPS TUESDAY INTO WEDNESDAY AHEAD OF A
CLIPPER SYSTEM MOVING ACROSS THE GREAT LAKES REGION. HIGH TEMPS
ON TUESDAY BACK IN THE 20S AND POSSIBLY UPPER 20S/LOWER 30S ON
WEDNESDAY. STILL SOME UNCERTAINTY FOR PRECIP CHANCES ACROSS THE
LOCAL AREA TUESDAY NIGHT INTO WEDNESDAY MORNING WITH THIS
CLIPPER. BLENDED GUIDANCE NOW HAS CHANCE POPS FOR THE NORTHERN
HALF OR SO OF THE AREA AND THAT SEEMS REASONABLE FOR NOW.
THERE REMAINS QUITE A BIT OF UNCERTAINTY FOR THE END OF NEXT
WEEK INTO NEXT WEEKEND WITH THE POTENTIAL FOR AN ACTIVE PATTERN
FOR OR NEAR THE LOCAL AREA. WHILE THE ENSEMBLES STILL SHOW A
DECENT SPREAD IN POSSIBILITIES, THIS TIME PERIOD HAS LOOKED
ACTIVE FOR THE PAST WEEK. REGARDLESS OF WHETHER PRECIP DEVELOPS
FOR THE LOCAL AREA, CURRENT TRENDS FAVOR A CONTINUED COLD/VERY
COLD PATTERN. CMS
AVIATION /18Z TAFS THROUGH 00Z MONDAY/
ISSUED AT 1123 AM CST SAT JAN 17 2026
ON-AND-OFF FLURRIES WILL CONTINUE THROUGH THE EARLY AFTERNOON AS
STRATOCUMULUS CLOUDS CENTERED IN THE DGZ STREAM OVERHEAD.
STEADY SNOW WILL DEVELOP/EXPAND ACROSS THE AREA AS A TROUGH AXIS
CURRENTLY STRETCHING FROM SOUTHERN WISCONSIN INTO CENTRAL IOWA
SHIFTS SOUTHEASTWARD. WHILE MOISTURE WILL BE MEAGER, LIFT
CENTERED DIRECTLY IN A LOW-CENTROID DGZ AND FILAMENTS OF
FRONTOGENESIS WILL SERVE TO CREATING DRY AND FLUFFY SNOW THAT
WILL BE EFFECTIVE AT LOWERING VISIBILITY. GENERALLY SPEAKING,
THE EXPECTATION IS FOR 2 TO 4 MILE VISIBILITY TO PREVAIL WITH
PERIODIC DROPS TO 1 TO 2 MILES FROM LATE AFTERNOON THROUGH EARLY
EVENING. CIGS SHOULD HOLD NEAR 2000 FT DURING THE PERIOD OF
SNOW, AND WINDS WILL REMAIN OUT OF THE SOUTH TO SOUTHWEST. TOTAL
ACCUMULATIONS OF A DUSTING TO LOCALLY 1 INCH REMAIN ON TRACK
FOR THE TERMINALS.
SNOW RATES WILL TAPER TO FLURRIES DURING THE OVERNIGHT HOURS AS
THE TROUGH AXIS SHEARS OUT WHILE SHIFTING EASTWARD. CIGS MAY
ATTEMPT TO SCATTER AFTER DAYBREAK AS WINDS BEGIN TO BACK
SOUTHWESTERLY.
YET ANOTHER CLIPPER SYSTEM WILL APPROACH THE REGION TOMORROW
AFTERNOON. WILL GO AHEAD AND INTRODUCE 3SM -SN TOWARD THE END OF
THE ORD/MDW 30-HOUR TAF WINDOWS, KEEPING IN MIND REFINEMENT IN
TIMING AND VISIBILITY WILL TAKE PLACE IN LATER TAF PACKAGES.
BORCHARDT
MARINE
ISSUED AT 330 AM CST SAT JAN 17 2026
A GALE WATCH REMAINS IN EFFECT LATE SUNDAY NIGHT THROUGH MONDAY
AFTERNOON FOR THE IL AND IN NEARSHORE WATERS.
AN ARCTIC COLD FRONT WILL MOVE ACROSS THE AREA SUNDAY NIGHT
BRINGING MUCH COLDER TEMPERATURES AND STRONG WINDS TO THE
REGION, WITH A PERIOD OF GALES EXPECTED LATE SUNDAY NIGHT
THROUGH AT LEAST MIDDAY MONDAY. FREEZING SPRAY IS ALSO EXPECTED,
ESPECIALLY FOR THE IN NEARSHORE WATERS. CMS
HYDROLOGY
ISSUED AT 253 PM CST FRI JAN 16 2026
THE UPCOMING EXTENDED PERIOD OF VERY COLD TEMPERATURES WILL LIKELY
RESULT IN THE RAPID DEVELOPMENT OF ICE ON AREA RIVERS AND STREAMS
WHICH MAY INCREASE THE CHANCE OF LOCALIZED ICE JAM FLOODING. LAST
WEEK'S HEAVY RAINFALL HAS RESULTED IN INCREASED STREAMFLOW IN
SEVERAL BASINS, INCLUDING THE FOX, DES PLAINS, AND ILLINOIS RIVER
BASINS. THIS HIGHER STREAMFLOW WILL RESULT IN A GREATER POTENTIAL
FOR FREEZE UP ICE JAM FLOODING.
- IZZI
LOT WATCHES/WARNINGS/ADVISORIES
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY UNTIL 9 PM CST THIS EVENING FOR WINTHROP
HARBOR IL TO GARY IN.
GALE WATCH FROM LATE SUNDAY NIGHT THROUGH MONDAY MORNING FOR
WINTHROP HARBOR IL TO GARY IN.
SMALL CRAFT ADVISORY UNTIL 3 AM CST SUNDAY FOR GARY TO BURNS
HARBOR IN-BURNS HARBOR TO MICHIGAN CITY IN.
GALE WATCH FROM LATE SUNDAY NIGHT THROUGH MONDAY AFTERNOON FOR
GARY TO BURNS HARBOR IN-BURNS HARBOR TO MICHIGAN CITY IN.
VISIT US AT WEATHER.GOV/CHICAGO
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page