689
FXUS63 KLOT 201759
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
1159 AM CST TUE JAN 20 2026
KEY MESSAGES
- ACCUMULATING SNOW IS EXPECTED LATE THIS EVENING THROUGH EARLY
WEDNESDAY MORNING NEAR AND NORTH OF INTERSTATE 80, WITH
HIGHEST AMOUNTS (3-5") POSSIBLE NEAR THE WI/IL STATE LINE.
- A STRONG ARCTIC FRONT MAY BRING A PERIOD OF GUSTY SNOW SHOWERS
WEDNESDAY EVENING FOLLOWED BY PATCHY BLOWING SNOW OVERNIGHT.
- A SECOND ARCTIC FRONT WILL USHER IN AN EXTENDED PERIOD OF
DANGEROUS COLD THURSDAY NIGHT THROUGH EARLY NEXT WEEK.
DISCUSSION
ISSUED AT 327 AM CST TUE JAN 20 2026
WE START OFF THE MORNING UNDER CLEAR SKIES AND BITTERLY COLD
CONDITIONS WITH WIND CHILLS IN THE -5 TO -15 RANGE ACROSS THE
AREA. A FEW LAKE EFFECT FLURRIES MAY LINGER THROUGH MID MORNING
ACROSS NORTHEAST PORTER COUNTY, OTHERWISE DRY CONDITIONS ARE
EXPECTED THROUGH THE AFTERNOON. INCREASING CLOUD COVERAGE
ARRIVES LATER IN THE DAY AHEAD OF AN APPROACHING CLIPPER SYSTEM.
TEMPERATURES WILL ALSO MODERATE SOME TODAY WITH HIGHS IN THE
20S FOR MOST AREAS, WITH UPPER TEENS NEAR THE WI/IL STATE LINE.
THE AFOREMENTIONED CLIPPER IS EXPECTED TO TRACK SOUTHEAST AND
ACROSS THE REGION LATER THIS EVENING THROUGH EARLY WEDNESDAY
MORNING. MODEL GUIDANCE HAS MOSTLY CONVERGED ON A NARROW SWATH
OF ACCUMULATING SNOW DEVELOPING ACROSS NORTHERN ILLINOIS LATER
THIS EVENING THROUGH THE OVERNIGHT HOURS, WITH THE HIGHEST
AMOUNTS FAVORED NEAR THE WI-IL STATE LINE. A FAIRLY DEEP LAYER
OF SATURATION SITUATED WITHIN THE DGZ PAIRED WITH MODEST ASCENT
WITHIN THAT LAYER SUPPORTS A PERIOD OF 0.5-1"/HR FLUFFY SNOWFALL
RATES SOMEWHERE WITHIN THE BROADER STRATIFORM BAND). HAVE
ACCORDINGLY MADE UPWARD ADJUSTMENTS IN QPF AND RESULTANT
SNOWFALL AMOUNTS ACROSS FAR NORTHERN ILLINOIS. WHILE SOME
WOBBLES IN THE SYSTEM'S EXACT TRACK REMAIN POSSIBLE, IN
COLLABORATION WITH NEIGHBORING OFFICES, WILL BE ISSUING A WINTER
WEATHER ADVISORY ON THIS SHIFT FOR THE NORTHERN TIER OF
ILLINOIS COUNTIES WHERE 3-5" OF SNOW ARE FORECAST, IN EFFECT
FROM 8 PM - 6 AM CST. LOCALIZED AMOUNTS WITHIN A NARROW BAND
APPROACHING 6" ARE NOT OUT OF THE QUESTION (COULD BE EITHER SIDE
OF WI/IL STATELINE). A SHIFT TO THE SOUTH COULD WARRANT A
SOUTHWARD EXPANSION OF THE ADVISORY WITH LATER UPDATES. WILL
ALSO HAVE TO KEEP AN EYE OUT ON THE POTENTIAL FOR A SOUTHWEST TO
NORTHEAST EXTENSION OF THE BAND TO DEVELOP NEAR AND EAST OF THE
I-55 CORRIDOR INTO EARLY WEDNESDAY MORNING AS THE SYSTEM IS
EXITING TO THE EAST, PER THE NAM/NAMNEST/RRFS. IF THIS WERE TO
OCCUR, HAZARDOUS TRAVEL IMPACTS COULD EXTEND FARTHER SOUTH AND
LATER INTO THE MORNING COMMUTE.
TEMPERATURES STILL LOOK TO WARM CLOSER TO SEASONABLE NORMS ON
WEDNESDAY AHEAD OF AN APPROACHING COLD FRONT WITH HIGHS IN THE
LOWER 30S SOUTH OF I-80, LINGERING SNOW PACK MAY HOLD
TEMPERATURES IN THE MID-UPPER 20S NORTH OF I-80/88. LOOKING
AHEAD TO WEDNESDAY EVENING, MODEL GUIDANCE HAS TRENDED TOWARD A
MORE ROBUST ARCTIC FRONTAL PASSAGE ACROSS THE AREA WITH STRONGER
WINDS DEVELOPING BEHIND THE FRONT PAIRED WITH GUSTY SNOW
SHOWERS (AND POSSIBLE EMBEDDED SQUALLS) ALONG IT. HAVE
ACCORDINGLY BUMPED OF SNOW SHOWER CHANCES TO "LIKELY" (60%) FOR
THE EVENING HOURS NEAR AND NORTH OF INTERSTATE-80 AND INCREASED
WIND GUSTS TO 35 MPH AREAWIDE WITH THE POTENTIAL FOR GUSTS TO
40+ MPH WITHIN ANY SNOW SHOWERS THAT DEVELOP. A QUICK 0.5-1" OF
SNOW COULD OCCUR AS IT MOVES THROUGH, MAINLY FALLING WITHIN A
1-2 HOUR PERIOD (OR LESS) AT ANY SINGLE LOCATION. THIS WILL BE A
PERIOD TO MONITOR CLOSELY IN THE EVENT THAT IT MOVES THROUGH
DURING THE LATTER PART OF THE EVENING COMMUTE. PATCHY BLOWING
SNOW MAY THEN LINGER THROUGH EARLY THURSDAY MORNING.
A SECOND ARCTIC FRONT DIVES SOUTH ACROSS THE AREA ON THURSDAY
WHICH WILL USHER IN AN EXTENDED PERIOD OF BITTER COLD THROUGH
EARLY NEXT WEEK AS SURFACE HIGH PRESSURE SETTLES ACROSS THE
REGION. SUB-ZERO LOW TEMPERATURES ARE FORECAST THURSDAY NIGHT
THROUGH MONDAY MORNING FOR AT LEAST PART OF THE LOCAL AREA,
COLDEST ACROSS INTERIOR NORTHERN ILLINOIS. DANGEROUS COLD IS
LOOKING INCREASINGLY LIKELY FOR THE THURSDAY NIGHT-EARLY FRIDAY
AM AND FRIDAY NIGHT-EARLY SATURDAY AM TIMEFRAME WHEN MINIMUM
WIND CHILLS COULD DROP INTO THE -20 TO -30 DEGREE RANGE.
WE WILL ALSO HAVE TO KEEP AN EYE ON THE WINTER STORM EXPECTED
TO IMPACT A LARGE PORTION OF THE COUNTRY TO OUR SOUTH. WHILE
THE MORE IMPACTFUL SNOW AND ICING IS FAVORED TO REMAIN WELL
SOUTH OF THE AREA, THERE ARE HINTS THAT THE BACK EDGE OF WHAT
COULD BE A VERY EXPANSIVE REGION OF SNOW COULD BRUSH PART OF
THE AREA OVER THE WEEKEND. STAY TUNED.
PETR
AVIATION /18Z TAFS THROUGH 00Z THURSDAY/
ISSUED AT 1159 AM CST TUE JAN 20 2026
- IFR CONDITIONS DUE TO SNOW EXPECTED TONIGHT INTO EARLY WED
MORNING
VFR CONDITIONS ARE EXPECTED THROUGH MUCH OF THIS EVENING BEFORE
A PERIOD OF SNOW OCCURS OVERNIGHT. STILL SOME UNCERTAINTY WITH
RESPECT TO THE START TIME OF THE SNOW, WITH SOME GUIDANCE
SUGGESTING SNOW MAY START 2 TO 3 HOURS LATER THAN INDICATED IN
TAFS, BUT WITH LOWER CONFIDENCE OPTED TO NOT MAKE ANY BIG
CHANGES TO THE PREVIOUS TAFS. STILL LOOKS LIKE AT LEAST A
SEVERAL HOUR PERIOD OF SNOW WITH IFR VSBY WITH THE THREAT FOR
OCNL LIFR VIS IN THE HEAVIER BURSTS OF SNOW, PARTICULARLY FOR
THE MORE NORTHERN TERMINALS (RFD, ORD, DPA). SNOW SHOULD END
EARLY WEDNESDAY MORNING WITH THE POTENTIAL FOR LINGERING MVFR
CIGS AS WESTERLY WINDS GRADUALLY INCREASE AND BECOME GUSTY AT
TIMES.
- IZZI
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...WINTER WEATHER ADVISORY FROM 8 PM THIS EVENING TO 6 AM CST
WEDNESDAY FOR ILZ003-ILZ004-ILZ005-ILZ006.
IN...NONE.
LM...NONE.
VISIT US AT WEATHER.GOV/CHICAGO
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