878
FXUS63 KLOT 212104
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
304 PM CST TUE JAN 21 2025
KEY MESSAGES
- WIND CHILLS OF -15F TO -20F WILL PERSIST THROUGH THIS EVENING.
THE COLD WEATHER ADVISORY REMAINS IN EFFECT UNTIL MIDNIGHT.
- ACCUMULATING SNOW (LOCALLY UP TO 1") IS EXPECTED WEDNESDAY
THROUGH EARLY THURSDAY MORNING LEADING TO SLIPPERY TRAVEL.
- LAKE EFFECT SNOW MAY LINGER ACROSS NORTHEAST PORTER COUNTY
DURING THE DAY ON THURSDAY.
DISCUSSION
ISSUED AT 304 PM CST TUE JAN 21 2025
THROUGH WEDNESDAY NIGHT:
AN ARCTIC HIGH CONTINUES TO SLIDE ACROSS THE MIDWEST AND GREAT
LAKES THIS AFTERNOON WHICH HAS RESULTED IN BITTERLY COLD
TEMPERATURES DESPITE THE NEARLY UNABATED SUNSHINE. HIGHS TODAY
HAVE LEVELED OFF AROUND 0 DEGREES AND LOOK TO REMAIN NEARLY
STATIONARY THROUGH SUNSET. WITH WINDS EXPECTED TO REMAIN BREEZY
THROUGH THIS EVENING, WIND CHILLS IN THE -15F TO -20F RANGE ARE
EXPECTED TO PREVAIL THROUGH MIDNIGHT. THEREFORE, THE COLD
WEATHER ADVISORY WAS EXTENDED UNTIL MIDNIGHT TO HIGHLIGHT THIS
THREAT.
AFTER MIDNIGHT, TEMPERATURES ARE EXPECTED TO GRADUALLY WARM AS
STRONG SOUTH-SOUTHWEST WINDS DEVELOP AND ADVECT IN "WARMER" AIR.
HOWEVER, TEMPERATURES ARE STILL EXPECTED TO BE IN THE SINGLE
DIGITS THROUGH THE NIGHT WITH WIND CHILLS HOVERING IN THE -10F
TO -15F RANGE. SINCE THESE WIND CHILL MAGNITUDES ARE ABOVE THE -20F
THRESHOLD USED FOR ADVISORIES, THE EXPECTATION IS FOR NO
ADDITIONAL COLD WEATHER HEADLINES TO BE ISSUED ONCE THE
AFOREMENTIONED ONE EXPIRES. THOUGH WIND GUSTS WILL BE INCREASING
INTO THE 20-25 MPH RANGE OVERNIGHT WHICH WILL KEEP A NOTABLE
CHILL IN THE AIR TO START OUR WEDNESDAY.
THE BROAD SHORTWAVE TROUGH CURRENTLY IN ALBERTA WILL BE
PIVOTING INTO THE NORTHERN PLAINS AND EVENTUALLY THE GREAT LAKES
THROUGH THE DAY ON WEDNESDAY. AS THIS OCCURS, THE SURFACE LOW
AHEAD OF THE SYSTEM WILL BE PIVOTING INTO THE NORTHERN GREAT
LAKES WHICH WILL FORCE A COLD FRONT TO ADVANCE ACROSS THE UPPER
MIDWEST WEDNESDAY MORNING. SNOW IS EXPECTED TO DEVELOP BENEATH
THIS WAVE AND ALONG THE COLD FRONT AND BEGIN TO MOVE INTO FAR
NORTHERN IL TOWARDS THE MID-MORNING AND EARLY AFTERNOON HOURS.
HOWEVER, THE FRONT IS FORECAST TO GET HUNG UP NEAR THE IL-WI
LINE WHICH SHOULD KEEP THE BULK OF THE SNOW ALONG THE STATE LINE
AND POINTS NORTH THROUGH MUCH OF THE DAY. THOUGH, THE FRONT IS
EXPECTED TO PIVOT SOUTHWARD THROUGH THE REST OF THE AREA LATE
WEDNESDAY AFTERNOON AND EVENING AS THE SHORTWAVE DIVES INTO THE
OHIO RIVER VALLEY. SINCE THE FRONT SHOULD BE FAIRLY PROGRESSIVE
AS IT MOVES ACROSS NORTHERN IL AND NORTHWEST IN, THE DURATION OF
SNOW AT ANY ONE LOCATION SHOULD BE ONLY 3-4 HOURS AT MOST AND
THUS KEEP ACCUMULATIONS AROUND HALF AN INCH. HOWEVER, LOCALLY
HIGHER TOTALS UP TO AN INCH ARE POSSIBLE ESPECIALLY NEAR THE IL-
WI LINE WHERE LONGEVITY IS FORECAST TO BE MAXIMIZED.
REGARDLESS, THE COLD SURFACE TEMPERATURES WILL ALLOW FOR SOME
SNOW COVERED ROADS AND SLIPPERY TRAVEL SO BE SURE TO USE CAUTION
IF TRAVELING TOMORROW.
SNOW IS EXPECTED TO GRADUALLY TAPER AFTER MIDNIGHT WEDNESDAY
NIGHT, THOUGH SOME LINGERING LIGHT SNOW AND FLURRIES MAY PERSIST
INTO THURSDAY MORNING FOR AREAS EAST OF I-57. OTHERWISE, EXPECT
TEMPERATURES TO WARM INTO THE 20S WEDNESDAY AFTERNOON BEFORE
COOLING INTO THE TEENS WEDNESDAY NIGHT. WINDS WILL ALSO BE GUSTY
ON WEDNESDAY AS THE SYSTEM MOVES THROUGH WITH GUSTS IN THE
25-30 MPH RANGE LIKELY AND LOCALLY HIGHER GUSTS POSSIBLE. THOUGH
WINDS WILL SUBSIDE WEDNESDAY EVENING AS THE SYSTEM BEGINS TO
EXIT TO OUR EAST.
YACK
THURSDAY THROUGH TUESDAY:
SNOW WILL BE WINDING DOWN TOWARD DAYBREAK ON THURSDAY THOUGH A
FEW FLURRIES MAY LINGER NEAR/SOUTHEAST OF I-55 THROUGH MID
MORNING. CONDITIONS BECOME FAVORABLE FOR LAKE EFFECT SNOW
ORIENTED INTO NORTHEAST PORTER COUNTY DURING THE DAY ON THURSDAY
(NORTHWESTERLY FETCH, DEEPENING INVERSION HEIGHTS, STEEP LAPSE
RATES AND SATURATION THROUGH THE DGZ) WHICH COULD RESULT IN
ADDITIONAL ACCUMULATIONS (LOCALLY UP TO 0.5-1") AND CONTINUED
SLICK TRAVEL. CLOUD DEPTHS BEGIN TO THIN TOWARD THURSDAY EVENING
WITH THE MAIN AREA OF SNOW SHIFTING FURTHER EAST.
WINDS WILL BE BREEZY OUT OF THE NORTHWEST IN THE WAKE OF A COLD
FRONTAL PASSAGE THURSDAY MORNING WHICH COMBINED WITH
TEMPERATURES ONLY WARMING INTO THE UPPER TEENS TO LOWER 20S WILL
RESULT IN WIND CHILLS IN THE SINGLE DIGITS PERSISTING DURING
THE DAY. LOW TEMPERATURES THURSDAY NIGHT DROP INTO THE SINGLE
DIGITS ONCE AGAIN AREAWIDE WITH WIND CHILLS IN THE 0 TO -10
DEGREE RANGE. MORE OF THE SAME IS EXPECTED ON FRIDAY WITH HIGHS
IN THE LOWER 20S. A RETURN TO SOUTHWESTERLY FLOW FRIDAY NIGHT
SHOULD ALLOW TEMPERATURES TO SLOWLY RISE THROUGH THE NIGHT WITH
TEMPERATURES ON SATURDAY CURRENTLY FORECAST TO BRIEFLY WARM
ABOVE FREEZING (33-36F) IN THE AFTERNOON.
WHILE THERE REMAINS VARIABILITY IN THE HANDLING OF THE UPPER
LEVEL PATTERN INTO EARLY NEXT WEEK, THE GENERAL EXPECTATION IS
FOR AN ELONGATED POSITIVELY TILTED UPPER LEVEL TROUGH
(POTENTIALLY CUT-OFF LOW) TO DEVELOP ACROSS THE WESTERN CONUS
WITH QUASI-ZONAL FLOW EXTENDING EAST. THIS PATTERN LARGELY
FAVORS KEEPING MORE MOISTURE LADEN WEATHER DISTURBANCES LARGELY
SOUTH OF THE AREA AND IS SUPPORTED BY THE LATEST ENSEMBLE
GUIDANCE KEEPING PROBS FOR >0.1" OF PRECIPITATION GENERALLY
UNDER 20% THROUGH EARLY NEXT WEEK.
PETR
AVIATION /18Z TAFS THROUGH 00Z THURSDAY/
ISSUED AT 1157 AM CST TUE JAN 21 2025
OTHER THAN FEW/SCT MVFR STRATOCUMULUS THIS AFTERNOON, VFR
CONDITIONS ARE EXPECTED THROUGH TONIGHT. W/WSW WINDS GUSTING
OVER 20 KNOTS AT TIMES TODAY WILL DIMINISH TO AROUND 10 KNOTS
WHILE BACKING SW THIS EVENING. SW WINDS WILL THEN INCREASE AGAIN
WITH GUSTS UP TO AROUND 25 KNOTS OVERNIGHT AS A LOW-LEVEL JET
DEVELOPS OVER THE AREA.
AN AREA OF WARM-AIR ADVECTION AND INCOMING MOISTURE ALOFT WILL
RESULT IN A WSW TO ENE BAND OF SNOW SOMEWHERE ACROSS FAR
NORTHERN ILLINOIS AND SOUTHERN WISCONSIN MID TO LATE MORNING
WEDNESDAY. WHILE THE LATEST INDICATIONS ARE THAT THE SN BAND
WILL STAY JUST NORTH OF THE CHICAGO TERMINALS, THERE REMAINS A
HIGH ENOUGH CHANCE TO INCLUDE A PROB30 FOR SN WITH IFR
VISIBILITY ROUGHLY 14-18Z BEFORE THE SN BAND LIFTS WELL NORTH OF
THE AREA.
OTHERWISE, SW WINDS WILL CONTINUE TO GUST TO 25 KNOTS OR HIGHER
FOR MUCH OF THE DAY TUESDAY, WITH THE POTENTIAL FOR GUSTS
SURPASSING 30 KNOTS EARLY TO MID AFTERNOON.
KLUBER
LOT WATCHES/WARNINGS/ADVISORIES
IL...COLD WEATHER ADVISORY UNTIL MIDNIGHT CST TONIGHT FOR ILZ003-
ILZ004-ILZ005-ILZ006-ILZ008-ILZ010-ILZ011-ILZ012-ILZ013-
ILZ019-ILZ020-ILZ021-ILZ023-ILZ032-ILZ033-ILZ039-ILZ103-
ILZ104-ILZ105-ILZ106-ILZ107-ILZ108.
IN...COLD WEATHER ADVISORY UNTIL MIDNIGHT CST /1 AM EST/ TONIGHT
FOR INZ001-INZ002-INZ010-INZ011-INZ019.
LM...SMALL CRAFT ADVISORY FROM 10 PM THIS EVENING TO 6 PM CST
WEDNESDAY FOR THE IL AND IN NEARSHORE WATERS.
VISIT US AT WEATHER.GOV/CHICAGO
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page