975
FXUS63 KLOT 060546
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
1146 PM CST FRI DEC 5 2025
KEY MESSAGES
- THERE REMAINS A LOW (20-30%) CHANCE FOR A FEW SNOW SHOWERS AND
PATCHES OF FREEZING DRIZZLE, MAINLY NORTH OF I-80 OVERNIGHT.
- A CLIPPER SYSTEM WILL DELIVER A SWATH OF SNOW IN OUR REGION
SATURDAY NIGHT INTO SUNDAY.
- LIGHT LAKE EFFECT SNOW MAY AFFECT PORTIONS OF NORTHWEST
INDIANA AND NORTHEAST ILLINOIS SUNDAY NIGHT INTO MONDAY
MORNING.
UPDATE
ISSUED AT 930 PM CST FRI DEC 5 2025
AN INITIAL SHORTWAVE AND ASSOCIATED PRE-FRONTAL TROUGH ARE
MOVING OVERHEAD, PRESENTLY WITHOUT MUCH FANFARE. DEWPOINTS ARE
RUNNING SIGNIFICANTLY LOWER THAN PREVIOUS GUIDANCE INDICATED,
AND COUPLED WITH THE ALREADY MEAGER MID-LEVEL MOISTURE PROFILES,
HAS RELEGATED MOST SNOWFALL NEAR AND NORTH OF THE WISCONSIN
STATE LINE. HAVE TRIMMED POPS A BIT THROUGH THE EVENING AND
OVERNIGHT, AND TRANSITIONED MOST PRECIPITATION OVER JUST TO
LIGHT SNOW (HAVE NOTED A FEW FLURRIES AT OUR OFFICE RECENTLY).
CLOUD TOP TEMPERATURES REMAIN MARGINAL TO SUPPORT CLOUD ICE,
BUT EVEN IF THINGS WERE TO TRY TO FLIP TO DRIZZLE, CLOUD
CEILINGS APPEAR TOO HIGH TO SUPPORT IMPACTFUL FREEZING DRIZZLE
THROUGH MUCH OF THE NIGHT.
FARTHER UPSTREAM, CURRENTLY NOTING AN A LOCALIZED CORRIDOR OF
IFR (SUB 1000 FOOT) CEILINGS STRETCHING FROM NORTH-CENTRAL IOWA
ACROSS THE WESTERN UP OF MICHIGAN. AUTOMATED OBSERVATIONS OF 2
TO 5 MILE MIST WITHIN THIS AXIS OF DEEPER NEAR-SURFACE MOISTURE
MAY BE SOME VERY LIGHT DRIZZLE, AND HAVE RECENTLY SEEN A FEW
MPING REPORTS OF FREEZING DRIZZLE. RECENT GUIDANCE INDICATES
SOME CORRIDORS OF NEAR-SURFACE CONVERGENCE ACCOMPANYING THIS
REGION OF LOWER CEILINGS INTO PARTS OF OUR AREA AFTER ~3 AM, AND
PERSISTING INTO THE MORNING. CLOUD DEPTHS ARE REALLY ON THE
MARGINAL SIDE FOR SUPPORTING DRIZZLE, SO NO PLANS ON ADDING
EXTRA MENTIONS INTO THE FORECAST INTO SATURDAY MORNING RIGHT
NOW BUT WILL KEEP A CLOSE EYE ON THINGS.
CARLAW
DISCUSSION
ISSUED AT 215 PM CST FRI DEC 5 2025
TONIGHT THROUGH SUNDAY:
A LOW-AMPLITUDE UPPER-LEVEL WAVE CONTINUES TO PROPAGATE
EASTWARD ACROSS THE UPPER MISSISSIPPI RIVER VALLEY, AND IS
GENERATING A BROAD REGION OF SNOW ACROSS SOUTHERN WISCONSIN, FAR
NORTHERN IOWA, AND WESTERN WISCONSIN. AS THE WAVE SHIFTS
EASTWARD THIS EVENING AND OVERNIGHT, IT WILL GRADUALLY WEAKEN
LEADING TO CORRESPONDING WEAKENING LIFT. FORECAST SOUNDINGS
CONTINUE TO DEPICT MARGINAL TEMPERATURES FOR SNOWFLAKE
PRODUCTION, AND INDEED, HAVE NOTED A FEW INTERMITTENT REPORTS OF
FREEZING DRIZZLE PRIMARILY ACROSS FAR NORTHERN IOWA THIS
AFTERNOON. SO, THE INHERITED FORECAST CALLING FOR SNOW SHOWERS
AND PERHAPS A FEW PATCHES OF FREEZING DRIZZLE ALONG AND NORTH OF
I-80 THROUGH THE OVERNIGHT HOURS REMAINS ON TRACK.
A NARROW SURFACE PRESSURE RIDGE WILL SLIDE THROUGH THE AREA
TOMORROW, LEADING TO A BRIEF PERIOD OF QUIET WEATHER. WITH
LITTLE CHANGE IN THE AIRMASS AND SNOWPACK BETWEEN TODAY AND
TOMORROW, AS WELL AS THE EXPECTATION FOR LINGERING CLOUDS, FELT
PERSISTENCE WAS THE WAY TO GO IS FOR HIGH TEMPS TO BE SIMILAR TO
TODAY AND IN THE MID UPPER 20S.
ATTENTION THEN TURNS TO A CLIPPER SYSTEM DUE TO RACE FROM THE
NORTHERN PLAINS TOMORROW AND INTO THE GREAT LAKES SATURDAY NIGHT
THROUGH MID-SUNDAY MORNING. CAM GUIDANCE SEEMS TO FAVOR A
STRONGER, WETTER, WARMER, AND FURTHER NORTHWARD EVOLUTION OF THE
SYSTEM, WITH FORECAST SOUNDINGS DEPICTING A 3 TO 6 HOUR WINDOW
WHERE LIFT WOULD BE MAXIMIZED JUST BENEATH THE DGZ (IDEAL). IN
FACT, FORECAST THERMAL PROFILES GET PRECARIOUSLY CLOSE TO
TRANSITIONING TOWARD A WINTRY MIX OR EVEN RAIN WITH SOUTHWARD
EXTENT AS SURFACE TEMPERATURES WARM TOWARD FREEZING. IN ALL, THE
STRONGER/NORTHERN SCENARIO WOULD LEAD TO A QUICK HIT OF 3 TO 5
INCHES OF SNOW, ESPECIALLY ALONG AND NORTH OF I-80. MEANWHILE,
GLOBAL GUIDANCE AND ENSEMBLE MEANS REMAIN MORE MUTED, LESS
AMPLIFIED, AND COLDER WITH TEMPERATURES REMAINING IN THE 20S AND
THE GREATEST LIFT DISPLACED WELL BENEATH THE DGZ (SMALL
SNOWFLAKES). SUCH A SCENARIO WOULD LEAD TO A BROAD SWATH OF 1 TO
3 INCHES OF SNOW CENTERED NEAR AND SOUTH OF I-80.
FOR NOW, WILL GENTLY NUDGE THE FORECAST TOWARD A BLEND OF BOTH,
LEADING TO A SWATH OF 0.15-0.3" OF QPF WITH RATIOS NEAR 12:1
TRANSLATING OF A BROAD SWATH OF 2 TO 4 INCHES OF SNOW ACROSS THE
AREA.
BORCHARDT
SUNDAY NIGHT THROUGH NEXT FRIDAY:
SURFACE HIGH PRESSURE WILL QUICKLY SHIFT ACROSS THE WESTERN
GREAT LAKES SUNDAY NIGHT INTO MONDAY. THE HIGH WILL BE SOMEWHAT
ELONGATED SW TO NE, WHICH WILL FAVOR NNE/NE LOW-LEVEL FLOW OVER
SOUTHERN LAKE MICHIGAN AND INTO NORTHERN ILLINOIS THROUGH THE
NIGHT. LIKELY DEVELOPMENT OF A LAND BREEZE OVER LOWER MICHIGAN
WILL ENHANCE THE MORE NORTHEASTERLY SHIFT. THIS WOULD NORMALLY
RESULT IN A FAVORABLE SET-UP FOR LAKE EFFECT SNOW INTO FAR
NORTHWEST INDIANA AND NORTHEAST ILLINOIS. HOWEVER, THERE ARE
SEVERAL LIMITING FACTORS THAT WILL GREATLY REDUCE LES POTENTIAL
DURING THIS TIME. WEAK SHORT-WAVE RIDGING WILL LOWER INVERSION
HEIGHTS TO OR SLIGHTLY BELOW 5KFT, ROUGHLY IN THE DGZ. ADDING IN
SOME LOW-LEVEL DRYING UPSTREAM, A MARGINAL SATURATED CLOUD
DEPTH ONLY POKING INTO THE DGZ WOULD YIELD LOWER SLR VALUES AND
SNOWFALL INTENSITY. HAVE INCLUDED UP TO AN INCH OF SNOW DURING
THE NIGHT NEAR THE LAKE, WITH THE POTENTIAL FOR A MORE FOCUSED
LES BAND AND/OR MESOLOW (FROM ENHANCED LAND BREEZE CONVERGENCE)
TO PRODUCE SLIGHTLY HIGHER SNOWFALL AMOUNTS.
THE SECOND SYSTEM IN THE EXTENDED WAVE TRAIN ACROSS THE REGION
WILL TRACK EASTWARD ACROSS LAKE SUPERIOR MONDAY NIGHT. AN AREA
OF SNOW FROM STRONG LOW-LEVEL WAA AND BROAD MID-LEVEL DIFFLUENCE
MAY BRUSH THE NORTHERN CWA WITH MINOR ACCUMULATIONS, BUT THE
LACK OF FULL TOP-DOWN SATURATION THIS FAR SOUTH PRECLUDES
INCLUDING HIGHER TOTALS OR MORE WIDESPREAD SNOW POTENTIAL.
THE NEXT, AND MUCH STRONGER, SYSTEM WILL SWING ACROSS THE
WESTERN GREAT LAKES LATE TUESDAY NIGHT INTO WEDNESDAY MORNING.
THE CWA WILL BE WELL WITHIN THE WARM SECTOR, WITH ROBUST LOW-
LEVEL WAA FROM MONDAY NIGHT THROUGH TUESDAY EVENING PUSHING
TEMPS ABOVE FREEZING. HOWEVER, IT REMAINS TO BE SEEN HOW THE
EROSION OF THE UPSTREAM SNOWPACK ACROSS MISSOURI AND SOUTHERN
ILLINOIS MODIFIES THE AIR MASS. WITH THAT SAID, THERMO PROFILES
INDICATE THAT ANY INITIAL SNOW (ALSO POSSIBLY SOME FREEZING
RAIN) WILL QUICKLY TRANSITION TO PREDOMINANTLY RAIN OVER MUCH OF
THE AREA THROUGH THE NIGHT. STRONG CAA WILL THEN CHANGE RAIN
BACK TO SNOW WEDNESDAY MORNING, WITH WINDY CONDITIONS AND
SCATTERED SNOW SHOWERS PERSISTING THROUGH THE DAY. STILL A LOT
OF DETAILS TO IRON OUT THIS FAR OUT IN TERMS OF PRECIP TYPE, BUT
PLAN FOR AT LEAST SOME WINTRY PRECIP AND POTENTIAL IMPACTS
TUESDAY EVENING AND/OR WEDNESDAY.
ACTIVE WEATHER WILL CONTINUE IN THE REGION THROUGH NEXT
WEEKEND, WITH THE POTENTIAL FOR A COUPLE ADDITIONAL CLIPPER-LIKE
SYSTEMS TO BRING WINTRY WEATHER OVER THE GREAT LAKES DURING
THIS TIME.
KLUBER
AVIATION /06Z TAFS THROUGH 12Z SUNDAY/
ISSUED AT 1145 PM CST FRI DEC 5 2025
KEY MESSAGES FOR THE 06Z TAF PERIOD:
* MVFR CIGS EXPECTED OVERNIGHT THROUGH EARLY SATURDAY AFTERNOON
(IFR POSSIBLE AT RFD).
* ACCUMULATING SNOW EXPECTED SATURDAY NIGHT INTO SUNDAY MORNING
WITH ASSOCIATED MVFR TO IFR VSBYS.
A COLD FRONT IS MOVING INTO NORTHERN ILLINOIS AS OF THIS
WRITING. OUT AHEAD OF IT, SCATTERED FLURRIES AND LIGHT SNOW
SHOWERS MOVED ACROSS CHICAGOLAND EARLIER THIS EVENING. WHILE THE
BONAFIDE SNOW SHOWER POTENTIAL APPEARS TO HAVE WRAPPED UP, A
FEW FLURRIES CAN'T BE RULED OUT OVERNIGHT.
MVFR CIGS WILL GRADUALLY EXPAND IN COVERAGE OVERNIGHT ACROSS THE
AREA WITH A PERIOD OF IFR POSSIBLE AT RFD. HAVE MAINTAINED A
RETURN TO VFR FOR MID-LATE AFTERNOON WITH THIS UPDATE THOUGH
GUIDANCE IS BEGINNING TO TREND TOWARD THE POSSIBILITY THAT MVFR
STRATUS COULD PERSIST THROUGH THE DAY.
WIDESPREAD ACCUMULATING SNOW WILL MOVE IN FROM THE WEST LATE
SATURDAY EVENING AND IMPACT ALL TAF SITES INTO SUNDAY MORNING.
LIGHT SNOW/FLURRIES MAY BEGIN AT RFD AROUND 03Z AND CHICAGOLAND
CLOSER TO 05-06Z, WITH STEADIER SNOWFALL AND ASSOCIATED MVFR TO
IFR CIGS AND VSBYS EXPECTED WITHIN A COUPLE OF HOURS THEREAFTER
THROUGH THE END OF THE TAF PERIOD.
SOUTHWEST WINDS LATE THIS EVENING WILL VEER WNW OVERNIGHT.
EXPECT WNW WINDS TO THEN CONTINUE THROUGH THE FIRST HALF OF THE
DAY ON SATURDAY, THEN BECOMING LIGHT AND VARIABLE LATE
AFTERNOON AHEAD OF THE SNOW. WINDS THEN SETTLE INTO A PREVAILING
SE DIRECTION AFTER SNOW BEGINS.
DOOM/PETR
LOT WATCHES/WARNINGS/ADVISORIES
IL...NONE.
IN...NONE.
LM...SMALL CRAFT ADVISORY UNTIL MIDNIGHT CST TONIGHT FOR THE IL AND
IN NEARSHORE WATERS.
VISIT US AT WEATHER.GOV/CHICAGO
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