844
FXUS63 KILX 232348
AFDILX
AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE LINCOLN IL
548 PM CST FRI JAN 23 2026
KEY MESSAGES
- A LONG-DURATION WINTER STORM WILL IMPACT THE REGION IN TWO WAVES
SPANNING LATE SATURDAY MORNING THROUGH SUNDAY EVENING. SNOW
AMOUNTS APPEAR FAIRLY LIGHT THROUGH THE DAY ON SATURDAY, WITH
ONLY AN INCH OR TWO OF SNOW (HIGHEST SOUTH OF I-70), HOWEVER,
MORE ACCUMULATING SNOW ARRIVES LATE SATURDAY NIGHT INTO SUNDAY.
- THERE WERE NO MAJOR FORECAST CHANGES TODAY. A WINTER STORM
WARNING REMAINS IN EFFECT FROM CASS TO VERMILION COUNTY AND
SOUTHWARD, WITH 5-10" OF TOTAL SNOW BEING THE MOST LIKELY
OUTCOME. THE HIGHEST SNOW TOTALS ARE EXPECTED NEAR/SOUTH OF
I-70, AND THERE IS 10-30% CHANCE FOR 12" OF SNOW (OR MORE).
NORTH OF THE WINTER STORM WARNING, 2-5" OF TOTAL SNOW IS
POSSIBLE.
- A COLD WEATHER ADVISORY REMAINS IN EFFECT THROUGH MIDDAY
SATURDAY. WIND CHILL VALUES WILL RANGE FROM 10 TO 20 DEGREES
BELOW ZERO TONIGHT INTO SATURDAY MORNING. ANOTHER COLD WEATHER
ADVISORY MAY BE NEEDED SUNDAY NIGHT INTO MONDAY MORNING (60-80%
CHANCE).
DISCUSSION
ISSUED AT 224 PM CST FRI JAN 23 2026
CLIMATOLOGICALLY, WE ARE AT THE COLDEST POINT IN THE WINTER SEASON
IN CENTRAL/SOUTHEAST ILLINOIS, AND THIS YEAR, WINTER IS NOT
HOLDING BACK. AN EXPANSIVE, ROBUST 1048-MB SFC HIGH PRESSURE
(NORMALIZED ANOMALY OF 2-3 STANDARD DEVIATIONS) REMAINS POSITIONED
OVER THE DAKOTAS, WITH AN ARCTIC AIR MASS PUSHING SOUTH INTO THE
SOUTHERN PLAINS/TN VALLEY. THE COLD WEATHER HEADLINES VERIFIED
THIS MORNING, WITH WIND CHILL VALUES OF 25 TO 35 BELOW FROM MACOMB
TO BLOOMINGTON AND NORTHWARD. WHILE WE SHOULD BE PAST THE MOST
EXTREME WIND CHILLS, THERE WILL BE LITTLE REPRIEVE FROM THE COLD
OVER THE NEXT WEEK. AIR TEMPERATURES REMAIN IN THE SINGLE DIGITS
NORTH OF I-70 THIS AFTERNOON.
IN TERMS OF THE UPCOMING WINTER STORM, THE BOTTOM LINE UP FRONT IS
THAT THERE HAS BEEN LITTLE CHANGE IN OUR THINKING FROM THE
PREVIOUS FORECAST. THERE IS STILL EXPECTED TO BE TWO WAVES OF
SNOW, ONE PRIMARILY LATE SAT MORNING- EARLY SAT EVENING, AND
ANOTHER BEGINNING AFTER MIDNIGHT SUN AND CONTINUING INTO SUN EVE.
THE SECOND OF THESE WAVES STILL LOOKS MORE ROBUST. THERE WILL BE A
SNOWFALL GRADIENT ACROSS THE ILX CWA WITH AMOUNTS DECREASING AS
YOU MOVE FROM SOUTHEAST ILLINOIS TO THE NORTHWEST. ONE OF THE
PRIMARY CHALLENGES THAT EXISTS WITH THIS FORECAST IS PINNING DOWN
WHERE EXACTLY THIS GRADIENT SETS UP AND HOW SHARP IT IS.
WHILE THERE WERE NO MAJOR SHIFTS IN THE FORECAST WITH THIS
PACKAGE, SUBTLE SHIFTS ARE STILL POSSIBLE OVER THE NEXT 24 HOURS.
THE STRENGTH AND LOCATION OF THE STRONG SFC HIGH PRESSURE TO THE
NORTH WILL ULTIMATELY IMPACT WHERE THE BAROCLINIC ZONE SETS UP.
WHILE SFC TEMPS AND THE LOW-LEVEL WARM NOSE WILL BOTH BE SOLIDLY
SOUTH OF OUR CWA, THE TEMPERATURE PROFILE OF THE ATMOSPHERE WILL
STILL IMPACT THE MICROPHYSICS OF THIS SNOW EVENT. IN SOME
LOCATIONS, FCST SOUNDINGS SHOW MUCH OF THE THERMAL PROFILE LOCATED
WITHIN THE DENDRITIC GROWTH ZONE (DGZ, WHICH IS -12 TO -18 DEGC),
WHICH FAVORS LARGE DENDRITES AND EFFICIENT SNOW RATES. IN OTHER
FCST SOUNDINGS, TYPICALLY THOSE FURTHER SOUTH, CLOSER TO THE
BAROCLINIC ZONE, THE SATURATED LAYER IS MOSTLY WARMER THAN THE
DGZ (IN THE -5 TO -10 DEGC RANGE), WHICH FAVORS COLUMN-SHAPED
SNOWFLAKES THAT ACCUMULATE LESS EFFICIENTLY. ALL OF THIS IS TO SAY
THAT DESPITE THE VERY COLD AIR MASS IN PLACE, WE MAY NOT REALIZE
THE HIGH LIQUID-SNOW RATIOS IN OUR FORECAST, WHICH WOULD CUT DOWN
ON THE SNOW TOTALS IN THE CURRENT DETERMINISTIC FORECAST (WHICH
HAS 8+" SOUTH OF I-70 FOR THE ENTIRE EVENT). THE THERMAL PROFILES
DO APPEAR MORE FAVORABLE HEADING INTO SUN, DURING WHICH TIME THE
QPF AMOUNTS ARE ALSO HIGHER, WHICH IS WHY WE ANTICIPATE GREATER
SNOWFALL AMOUNTS WITH THAT SECOND WAVE.
IMPACTS APPEAR FAIRLY LIMITED DURING THE DAY ON SATURDAY, WITH
JUST A 30-50% CHANCE OF 1" OF SNOW NORTH OF I-70 BY 6 PM SAT. THE
STRONGER PUSH OF SNOW MOVES IN AFTER MIDNIGHT SUN, AND WHILE THE
LATEST HREF (23.12Z) ONLY GOES OUT THROUGH 12Z/6AM SUN IT DOES
SUGGEST SNOW RATES APPROACHING 0.50"/HOUR SOUTH OF I-70 LATE IN
THE OVERNIGHT HOURS. RATES OF 0.25-0.50"/HOUR ARE EXPECTED WITHIN
THE WARNING AREA NORTH OF I-70. THESE RATES ARE LIKELY TO CONTINUE
INTO THE DAY ON SUN. THIS IS EXPECTED TO LEAD TO TRAVEL IMPACTS
WITHIN THE WINTER STORM WARNING/ADVISORY AREAS FROM LATE SATURDAY
NIGHT THROUGH MUCH OF THE DAYTIME HOURS ON SUNDAY (WITH SNOW
LINGERING IN EASTERN IL INTO THE EVENING). NORTH WINDS GUSTING
20-25 MPH ON SUN COMBINED WITH LIGHT SNOWFLAKES COULD LEAD TO
BLOWING/DRIFTING, WITH ANY IMPACTS MAXIMIZED ON EAST-WEST ORIENTED
ROADS.
DESPITE BEING WITHIN A DAY OR TWO OF THE EVENT, THE UNCERTAINTIES
REGARDING THE MICROPHYSICS, BAROCLINIC ZONE PLACEMENT, AND
POTENTIAL FOR A TIGHT NORTHERN GRADIENT DO LEAVE A GOOD DEAL OF
UNCERTAINTY IN THE FORECAST. THE HIGHEST END OUTCOMES INCLUDE OVER
A FOOT OF SNOW NEAR/SOUTH OF I-70 (10-30% CHANCE OF MORE), WHILE
THE OFFICIAL FORECAST FOR THE WINTER STORM WARNING IS 5-10". THERE
WERE INTERNAL DISCUSSIONS ABOUT EXPANDING THE WINTER WEATHER
ADVISORY TO INCLUDE KNOX, STARK, AND MARSHALL COUNTIES, WHERE 1-3"
OF SNOW IS CURRENTLY FORECAST, HOWEVER, GIVEN THE POTENTIAL FOR A
TIGHT NORTHERN GRADIENT WE HELD OFF FOR NOW. THERE WAS NOT ANY
CONSIDERATION GIVEN TO CHANGING THE WINTER STORM WARNING, THE
EXISTING WARNING APPEARED WELL POSITIONED.
*** NEXT WEEK ***
AS NOTED ABOVE, THE EXTENDED FORECAST SHOWS LITTLE IN THE WAY OF
RELIEF FROM THE COLD, AT LEAST FOR THE REMAINDER OF JANUARY.
ENSEMBLE GUIDANCE SUGGESTS HIGH TEMPS WILL GENERALLY BE BELOW 20
DEGF EACH DAY, WITH THE EXCEPTION OF TUESDAY (LOW/MID 20S).
ADDITIONALLY, SNOW COVER MAY RESULT IN TEMPS RUNNING COOLER THAN
GUIDANCE, ESPECIALLY ON LESS WINDY, CLEAR NIGHTS. WITH THAT IN
MIND, DID NUDGE THE LOW TEMP FORECAST COOLER MON NIGHT AND TUES
NIGHT, RESULTING IN LOWS NEAR ZERO. WIND CHILL VALUES MAY
APPROACH COLD WEATHER ADVISORY CRITERIA AT TIMES, PARTICULARLY SUN
NIGHT-MON MORNING (60-80% CHANCE PER LREF). AFTER OUR WEEKEND
SYSTEM DEPARTS, PRECIP CHANCES APPEAR LIMITED, AT LEAST DURING THE
FIRST HALF OF THE UPCOMING WORK WEEK. THE EXTENDED OUTLOOKS FROM
THE CPC STILL FAVOR BELOW NORMAL TEMPS (60-90% CHANCE) THROUGH
NEXT WEEKEND.
ERWIN
AVIATION
(FOR THE 00Z TAFS THROUGH 00Z SATURDAY EVENING)
ISSUED AT 548 PM CST FRI JAN 23 2026
VFR CONDITIONS WILL PREVAIL AT ALL TAF SITES THROUGH THE NIGHT AND
TOMORROW MORNING. THEN AS SNOW ARRIVES, CONDITIONS WILL BECOME
MORE MVFR, THE IFR DUE TO VISIBILITIES DROPPING TO 1-2SM WITH
-SN. HIGH CIGS TO START, THEN BECOMING MID CLOUDS AROUND 12KFT
THEN LOWERING TO 7-8KFT DURING THE LATE MORNING. ONCE SNOW
ARRIVES, CIGS WILL DROP TO MVFR BELOW 2KFT. WINDS WILL BE LESS
10KTS OF LESS THROUGH THE PERIOD WITH DIRECTION STARTING AS
NORTHERNLY AND THEN BECOMING NORTHEAST.
AUTEN
ILX WATCHES/WARNINGS/ADVISORIES
COLD WEATHER ADVISORY UNTIL NOON CST SATURDAY FOR ILZ027>031-
036>038-040>057-061>063-066>068.
WINTER WEATHER ADVISORY FROM 9 AM SATURDAY TO MIDNIGHT CST
SUNDAY NIGHT FOR ILZ029-031-036>038-040-041.
WINTER STORM WARNING FROM 9 AM SATURDAY TO MIDNIGHT CST SUNDAY
NIGHT FOR ILZ042>057-061>063-066>068-071>073.
COLD WEATHER ADVISORY UNTIL NOON CST SATURDAY FOR ILZ071>073.
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