759
FXUS63 KLOT 192058
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
258 PM CST MON JAN 19 2026
KEY MESSAGES
- VERY COLD CONDITIONS WILL CONTINUE THROUGH TUESDAY MORNING.
- A CLIPPER SYSTEM IS EXPECTED TO BRING ACCUMULATING SNOW TO
PARTS OF THE AREA TUESDAY NIGHT INTO WEDNESDAY MORNING,
ESPECIALLY FOR AREAS NEAR AND NORTH OF I-80.
- TWO COLD FRONTS, WEDNESDAY NIGHT AND THURSDAY NIGHT, MAY EACH
BRING A PERIOD OF LIGHT SNOW OR SNOW SHOWERS.
- ANOTHER PERIOD OF BITTERLY COLD TEMPERATURES EXPECTED
THURSDAY NIGHT THROUGH THIS WEEKEND.
DISCUSSION
ISSUED AT 258 PM CST MON JAN 19 2026
THROUGH TUESDAY:
VERY COLD CONDITIONS WILL CONTINUE INTO TUESDAY MORNING, THOUGH IT
WILL BE LESS UNCOMFORTABLE FEELING DUE TO MUCH LIGHTER WINDS. A
MOISTURE STARVED MID-LEVEL SHORT-WAVE WILL PIVOT ACROSS THE AREA
THIS EVENING AND EARLY OVERNIGHT. FOR THE MOST PART, THE MAIN
EFFECT ON SENSIBLE WEATHER WILL BE A PERIOD OF MOSTLY CLOUDY SKIES
AS THE SHORT-WAVE PASSES OVER THE REGION. HOWEVER, IT'S NOT AT
ALL UNCOMMON TO SEE A FEW FLURRIES LEAKING OUT OF THE STRATUS
DECK IN THESE SETUPS. THERE HAVE BEEN A COUPLE OBS OFF TO THE
NORTHWEST (SOUTHEAST MN, FAR NORTHEAST IA, WESTERN WI) WITH
HINTS OF MODEST VISIBILITY REDUCTIONS THIS AFTERNOON AND EVEN A
SITE OR TWO WITH LIGHT SNOW (FLURRIES) REPORTED.
HAD EARLIER INTRODUCED A MENTION OF FLURRIES IN THE GRIDDED
DATABASE THIS EVENING UNTIL A COUPLE HOURS PAST MIDNIGHT, AND
CONTINUED THAT THIS AFTERNOON. THESE WOULD BE IN THE FORM OF
ISOLATED STREAMERS OF VERY LIGHT (LIKELY NON-ACCUMULATING)
FLURRIES THAT MAY CAUSE SPORADIC BOUTS OF 3-6 MILE VISIBILITY DUE
TO VERY SMALL FLAKE SIZE (CLOUD BEARING LAYER COLDER THAN DGZ).
CLOUDS SHOULD THEN CLEAR OUT BY THE PRE-DAWN HOURS AS 1030 MB
SURFACE RIDGING EXTENDS TO THE LOCAL AREA FROM THE 1035 MB HIGH
PRESSURE CENTER TRANSITING THE MID SOUTH. TEMPERATURES SHOULD BE
ABLE TO DROP BACK TO THE 0 TO LOCALLY -5F RANGE FOR LOCATIONS
NEAR/NORTH OF I-80 OUTSIDE OF CHICAGO BY THE DIURNAL MINIMA JUST
PRIOR TO SUNRISE, AND INTO THE LOW POSITIVE SINGLE DIGITS
ELSEWHERE.
AFTER A MOSTLY SUNNY START TO THE DAY ON TUESDAY, MID AND HIGH
LEVEL CLOUD COVER WILL STREAM IN FROM THE WEST DURING THE
AFTERNOON IN ADVANCE OF OUR NEXT SNOW PRODUCING CLIPPER-TYPE SYSTEM
TUESDAY NIGHT (DETAILS IN NEXT SECTION). AFTERNOON HIGHS WILL
RANGE FROM THE UPPER TEENS NEAR THE WISCONSIN BORDER TO THE MID TO
LOCALLY UPPER 20S ON TUESDAY, COLDEST NEAR THE WISCONSIN BORDER
AND "MILDEST" IN FAR SOUTHWEST SECTIONS OF THE CWA.
CASTRO
TUESDAY NIGHT THROUGH MONDAY:
HIGH LATITUDE BLOCKING ACROSS ALASKA AND GREENLAND WILL FOSTER
ANOMALOUS TROUGHING ACROSS THE CENTRAL AND EASTERN CONUS THROUGH
THE FORECAST PERIOD. THIS LARGE SCALE PATTERN IS CONSISTENT
WITH THE NEGATIVE PHASE OF THE ARCTIC OSCILLATION, AND IS
STRONGLY CORRELATED WITH BELOW TO MUCH BELOW NORMAL TEMPERATURES
AND PERIODIC SNOW CHANCES FROM CLIPPER TYPE SYSTEMS ACROSS OUR
AREA. ACCORDINGLY, OUR PRIMARY CONCERNS THROUGH THE PERIOD FOCUS
ON THE THREAT FOR WHAT LOOKS TO BE ANOTHER PERIOD OF
DANGEROUSLY COLD WEATHER (PARTICULARLY FRIDAY INTO THE WEEKEND),
ALONG WITH THE INCREASING THREAT FOR ACCUMULATING SNOW FROM TWO
QUICK MOVING CLIPPER SYSTEMS (TUESDAY NIGHT AND WEDNESDAY
EVENING).
GLOBAL ENSEMBLE GUIDANCE CONTINUES TO BE IN GOOD AGREEMENT WITH
THE TIMING AND TRACK OF THE FIRST CLIPPER SYSTEM SHIFTING INTO
THE WESTERN GREAT LAKES TUESDAY NIGHT. WHILE THE 12Z HIRES
GUIDANCE FAVORS A FARTHER NORTH TRACK OF THE ACCUMULATING SNOW
TUESDAY NIGHT (MAINLY OVER SOUTHERN WI), WE HAVE OPTED TO FOLLOW
CLOSER TO THE MORE CONSISTENT GLOBAL GUIDANCE FOR THE FORECAST
TUESDAY NIGHT INTO WEDNESDAY AT THIS TIME. OVERALL, THIS FAVORS
DEVELOPING SNOW WITHIN A WARM AIR ADVECTION ZONE ACROSS MUCH OF
NORTHERN IL AND FAR NORTHWESTERN IN (ALONG AND NORTH OF I-80)
MID TO LATE TUESDAY EVENING. SNOW WOULD THEN CONTINUING DURING
THE OVERNIGHT HOURS, BEFORE ABATING AROUND (OR SHORTLY AFTER)
DAYBREAK WEDNESDAY MORNING. ACCUMULATIONS DO NOT LOOK OVERLY
HIGH WITH THIS CLIPPER, BUT THE POTENTIAL EXISTS FOR AMOUNTS OF
2-3" NORTH OF I-88, WITH GENERALLY AN INCH OR LESS SOUTHWARD
TOWARDS THE I-80 CORRIDOR (AND LITTLE TO NO ACCUMULATION WELL
SOUTH OF I-80). ACCORDINGLY, EXPECT UNTREATED ROADS FROM I-80
NORTHWARD TO BECOME SNOW COVERED AND SLICK INTO THE EARLY
WEDNESDAY MORNING COMMUTE.
FOLLOWING THE END OF THE SNOW EARLY WEDNESDAY MORNING,
TEMPERATURES MAY WARM TO NEAR FREEZING DURING THE AFTERNOON IN
PARTS OF THE AREA JUST IN ADVANCE OF OUR NEXT QUICKLY
APPROACHING CLIPPER SYSTEM AND COLD FRONT SET TO SHIFT ACROSS
THE AREA WEDNESDAY EVENING. ANOTHER RATHER QUICK (2 TO 4 HOUR)
"THUMP" OF SNOW SHOWERS LOOKS TO ACCOMPANY THIS FRONT WEDNESDAY
EVENING. THIS MAY THUS RESULT IN SOME ADDITIONAL MINOR
ACCUMULATIONS, AND A PERIOD OF SLICK TRAVEL BEFORE TAPERING TO
FLURRIES BY MIDNIGHT WEDNESDAY NIGHT.
THE MAIN WEATHER STORY LATER IN THE WEEK CONTINUES TO FOCUS ON
THE TURN BACK INTO A PERIOD OF DANGEROUSLY COLD WEATHER
(PARTICULARLY FRIDAY INTO SATURDAY) FOLLOWING A STRONG ARCTIC
COLD FRONT AND POSSIBLE QUICK PERIOD OF SNOW SHOWERS THURSDAY
NIGHT. DURING THIS PERIOD, ENSEMBLE GUIDANCE FAVORS THE HIGH
LATITUDE BLOCKING TO FORCE A SIGNIFICANT SOUTHWARD SHIFT OF A
PIECE OF THE POLAR VORTEX INTO SOUTHERN CANADA AND THE UPPER
GREAT LAKES REGION. AT THE SURFACE, THIS WOULD BE LIKELY TO
DRIVE A 1050+ MB POLAR SURFACE HIGH AND ACCOMPANYING AIRMASS
SOUTHEASTWARD ACROSS SASKATCHEWAN AND THE DAKOTAS INTO THE
WESTERN GREAT LAKES FRIDAY INTO SATURDAY. THE MAGNITUDE OF THIS
POLAR AIRMASS COULD END UP RESULTING IN TEMPERATURES REMAINING
BELOW ZERO FOR AFTERNOON HIGH TEMPERATURES ON FRIDAY, WITH TEENS
BELOW ZERO TEMPERATURES AT NIGHT.
WE WILL ALSO HAVE TO KEEP AN EYE ON THE EVOLUTION OF WHAT COULD
BE A MAJOR WINTER STORM ACROSS MUCH OF THE SOUTHERN CONUS
FRIDAY INTO SATURDAY. AT THIS TIME, IT APPEARS WE MAY BE LOCKED
DEEP ENOUGH IN THE POLAR AIRMASS TO KEEP ALL OF THE WINTRY
PRECIPITATION SAFELY TO OUR SOUTH, BUT WE WILL CONTINUE TO
MONITOR THIS.
KJB
AVIATION /18Z TAFS THROUGH 00Z WEDNESDAY/
ISSUED AT 1127 AM CST MON JAN 19 2026
KEY AVIATION MESSAGES FOR THE CURRENT TAF PERIOD:
- GUSTY WEST-NORTHWEST WINDS EXPECTED TO DIMINISH THROUGH THE
AFTERNOON. PATCHY BLOWING SNOW POSSIBLE DURING STRONGEST
GUSTS.
- CHANCE FOR FLURRIES OVERNIGHT, BUT NO ACCUMULATIONS OR IMPACTS
TO VIS/CIGS EXPECTED.
AS CLOUD COVER HAS DIMINISHED OVER THE AIRSPACE, THE MAIN
IMPACTS TO AREA TERMINALS IS FROM THE GUSTY WEST TO NORTHWEST
WIND GUSTS. GUSTS ARE STILL REACHING UP TO 30 KNOTS AT THE TIME
THIS DISCUSSION WAS PUBLISHED. GUSTY WINDS WILL REMAIN THROUGH
THE AFTERNOON, BUT GENERALLY SUBSIDE THROUGH SUNSET. LOCALIZED
BLOWING SNOW WILL BE POSSIBLE THIS AFTERNOON, BUT AS THE WINDS
DIMINISH, THE RISK FOR BLOW SNOW WILL ALSO DECREASE.
A WEAK WAVE IS EXPECTED TO DROP DOWN FROM WISCONSIN OVERNIGHT
TONIGHT. WHILE THIS WAVE WILL NOT BE OVERLY IMPACTFUL, CANNOT
RULE OUT THE CHANCE FOR A FEW NON-IMPACTFUL/NON-ACCULUATIONG
FLURRIES BUT CONFIDENCE IS LOW. WINDS WILL BECOME MORE SOUTHERLY
TOMORROW WITH A CHANCE FOR SOUTHEAST WINDS BY THE END OF THE
TAF WINDOW.
DK
HYDROLOGY
ISSUED AT 258 PM CST MON JAN 19 2026
AREA HYDROGRAPHS AND ICE SPOTTER REPORTS CONFIRM THAT ICE
CONTINUES TO DEVELOP AND SPREAD ACROSS AREAL RIVERS. LOCALIZED ICE
JAMS ARE ALREADY PRESENT ALONG THE ROCK, DES PLAINES, AND FOX
RIVERS. CONTINUED COLD TEMPERATURES TONIGHT AND TUESDAY WILL
CAUSE ICE TO CONTINUE EXPANDING AND THICKENING.
AFTER A BRIEF WARM-UP IN TEMPERATURES TO ABOVE 20 DEGREES ON
TUESDAY-WEDNESDAY, ANOTHER PUSH OF BITTERLY COLD TEMPERATURES
WILL ARRIVE THURSDAY NIGHT. AS A RESULT, THE THREAT FOR ICE
JAMS INCLUDING LOCALIZED FLOODING WILL INCREASE FURTHER TOWARD
THE END OF THE WEEK AND THROUGH THE WEEKEND.
- NWS CHICAGO
LOT WATCHES/WARNINGS/ADVISORIES
IL...NONE.
IN...NONE.
LM...GALE WARNING UNTIL 3 PM CST THIS AFTERNOON FOR THE IL AND IN
NEARSHORE WATERS.
SMALL CRAFT ADVISORY UNTIL 3 AM CST TUESDAY FOR WINTHROP
HARBOR IL TO GARY IN.
HEAVY FREEZING SPRAY WARNING UNTIL 9 PM CST THIS EVENING FOR
GARY TO BURNS HARBOR IN-BURNS HARBOR TO MICHIGAN CITY IN.
SMALL CRAFT ADVISORY UNTIL 10 AM CST TUESDAY FOR GARY TO BURNS
HARBOR IN-BURNS HARBOR TO MICHIGAN CITY IN.
VISIT US AT WEATHER.GOV/CHICAGO
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