874
FXUS63 KLOT 171930
AFDLOT
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL
130 PM CST MON FEB 17 2025
KEY MESSAGES
- BITTERLY COLD CONDITIONS ARE EXPECTED THROUGH THURSDAY
MORNING. A COLD WEATHER ADVISORY REMAINS IN EFFECT FOR ALL IL
COUNTIES TONIGHT INTO TUESDAY MORNING.
- THERE IS A 30-40% CHANCE FOR LAKE EFFECT SNOW TO ACCUMULATE IN
PORTIONS OF PORTER COUNTY, IN TUESDAY THROUGH WEDNESDAY.
- THERE IS A LOW (20-40%) CHANCE OF SOME LIGHT ACCUMULATING SNOW
AND ASSOCIATED TRAVEL IMPACTS AREAWIDE LATE WEDNESDAY INTO
WEDNESDAY EVENING.
- TEMPERATURES GRADUALLY WARM BACK TOWARD AND EVEN ABOVE NORMAL
INTO EARLY NEXT WEEK.
DISCUSSION
ISSUED AT 130 PM CST MON FEB 17 2025
THROUGH TUESDAY NIGHT:
PRIMARY FORECAST CONCERN REMAINS THE BITTERLY COLD TEMPERATURES.
WHILE SKIES WILL LIKELY BE MOSTLY CLOUDY FOR MUCH OF THIS
EVENING, SOME CLEARING IS EXPECTED OVERNIGHT, ESPECIALLY ACROSS
THE NORTHERN CWA. THUS, LOW TEMPS IN THE SINGLE DIGITS BELOW
ZERO STILL ON TRACK. THE CLOUD COVER MAY PERSIST ACROSS THE
SOUTHERN CWA, ALONG WITH SOME LOWER LAKE EFFECT CLOUD COVER
ACROSS PARTS OF NORTHWEST IL, WHICH MAY KEEP TEMPS A BIT WARMER
THAN CURRENTLY EXPECTED. NET AFFECT OF ALL THIS IS TO MAINTAIN
THE CURRENT COLD WEATHER ADVISORY AS IS, WITH NO CHANGES. HIGH
TEMPS ON TUESDAY WILL LIKELY BE SIMILAR TO TODAY, HIGH SINGLE
DIGITS NORTH TO LOWER/MID TEENS SOUTH.
THERE WILL BE A CHANCE OF LIGHT SNOW ACROSS THE FAR SOUTHERN CWA
LATE THIS AFTERNOON INTO THIS EVENING. THE BULK OF ANY
ACCUMULATING SNOW IS EXPECTED TO BE SOUTH OF THE AREA, BUT A
DUSTING IN THE FAR SOUTHERN CWA IS POSSIBLE. A FEW FLURRIES WILL
BE POSSIBLE ELSEWHERE.
AS WINDS TURN MORE NORTH/NORTHWEST TONIGHT, LAKE EFFECT SNOW
WILL BE POSSIBLE ACROSS PORTER COUNTY IN NORTHWEST IN, THOUGH
THERE REMAINS UNCERTAINTY FOR HOW FAR INTO PORTER COUNTY ANY
SNOW MAY DEVELOP AND HOW ORGANIZED IT MAY BECOME. CURRENT CHANCE
POPS SEEM REASONABLE FOR NOW. THIS LAKE EFFECT SNOW POTENTIAL
LOOKS TO CONTINUE THROUGH TUESDAY AND INTO TUESDAY NIGHT AND
JUST DUE TO THIS LONGER DURATION, A FEW INCHES OF SNOW
ACCUMULATION MAY BE POSSIBLE ACROSS NORTHEAST PORTER COUNTY.
INCREASING CLOUD COVER TUESDAY NIGHT MAY KEEP TEMPS A BIT
WARMER, ESPECIALLY ACROSS THE CENTRAL/SOUTHERN CWA WHERE LOWS
MAY REMAIN IN THE LOW/MID SINGLE DIGITS ABOVE ZERO, PERHAPS NEAR
ZERO IN THE NORTHWEST. WITH THESE TEMPS, COLDEST WIND CHILLS
WOULD BE IN THE -10 TO -15 RANGE AND ABOVE ADVISORY CRITERIA.
CMS
WEDNESDAY THROUGH MONDAY:
COLD CONDITIONS PERSIST THROUGH THE REMAINDER OF THE WORK WEEK AS
A STRONG 1045+ MB CANADIAN HIGH GRADUALLY SETTLES SOUTHWARD ALONG
THE MISSOURI RIVER VALLEY WEDNESDAY AND THURSDAY. THROUGH
THURSDAY, THE AIRMASS EAST OF THIS HIGH WILL CONTINUE TO FOSTER
DAILY HIGHS IN THE TEENS, WITH OVERNIGHT LOWS RANGING FROM THE
SINGLE DIGITS ABOVE ZERO TO THE SINGLE DIGITS BELOW ZERO (COLDEST
INTERIOR SECTIONS OF NORTHERN IL). SUBZERO WIND CHILLS ARE ALSO
EXPECTED THROUGH THURSDAY MORNING. FORTUNATELY, CONDITIONS WILL
BEGIN A GRADUAL WARMING TREND INTO THIS WEEKEND AS SURFACE WINDS
TURN SOUTHWESTERLY FOLLOWING THE EASTWARD DEPARTURE OF THIS
CANADIAN HIGH. WE CURRENTLY ANTICIPATE TEMPERATURES WARMING BACK
INTO THE MID TO UPPER 30S BY SUNDAY, WHICH IS NEAR THE
CLIMATOLOGICAL NORMAL FOR THIS TIME OF YEAR. EVEN WARMER WEATHER
LOOKS TO BE ON TAP FOR A PERIOD EARLY NEXT WEEK.
WITH THE PRESENCE OF THIS DRY ARCTIC AIRMASS, LITTLE IN THE WAY OF
PRECIPITATION (OUTSIDE OF LAKE EFFECT) IS EXPECTED THROUGH THE
REMAINDER OF THE WORK WEEK. THE ONLY EXCEPTION BEING LATE
WEDNESDAY INTO WEDNESDAY EVENING AS A RATHER STOUT PV ANOMALY IS
SLATTED TO SHIFT ACROSS NORTHERN IL. WHILE FORECAST GUIDANCE IS
NOT SHOWING MUCH IN THE WAY OF QPF WITH THIS FEATURE, FORECAST
SOUNDINGS SUGGEST THE POTENTIAL FOR A PERIOD OF DRY LIGHT SNOW.
WE DON'T ANTICIPATE MUCH SNOW WITH THIS, BUT WITH THE AIRMASS
BEING SO COLD, SOME LIGHT COATINGS CANNOT BE RULED OUT.
ACCORDINGLY, WE HAVE MAINTAINED SOME LOW (20-40%) CHANCES FOR SNOW
IN THE FORECAST FOR WEDNESDAY EVENING.
KJB
AVIATION /18Z TAFS THROUGH 00Z WEDNESDAY/
ISSUED AT 1113 AM CST MON FEB 17 2025
- NO SIGNIFICANT CONCERNS THROUGH TUESDAY AFTERNOON.
BREEZY WEST/WEST-NORTHWEST WINDS WITH GUSTS TO 20-25 KT THIS
AFTERNOON WILL VEER TO NORTHWESTERLY THIS EVENING AND REMAIN
NORTHWESTERLY (PRIMARILY 300-330 DEG) THE REST OF THE PERIOD.
THERE MAY BE GUSTS TO AROUND 20 KT AT TIMES THIS EVENING AND
OVERNIGHT. ASIDE FROM LAKE EFFECT CLOUDS EAST OF THE NEAR LAKE
TERMINALS, A FEW TO SCATTERED CLOUDS AT 2500-3000 FT MAY DEVELOP
THIS AFTERNOON AND AGAIN ON TUESDAY AFTERNOON. WHILE SPORADIC
BKN HIGH MVFR CIGS CAN'T BE COMPLETELY RULED OUT, CONDITIONS
WILL BE PRIMARILY VFR.
CASTRO
LOT WATCHES/WARNINGS/ADVISORIES
IL...COLD WEATHER ADVISORY FROM 9 PM THIS EVENING TO NOON CST
TUESDAY FOR ILZ003-ILZ004-ILZ005-ILZ006-ILZ008-ILZ010-
ILZ011-ILZ012-ILZ013-ILZ019-ILZ020-ILZ021-ILZ023-ILZ032-
ILZ033-ILZ039-ILZ103-ILZ104-ILZ105-ILZ106-ILZ107-ILZ108.
IN...NONE.
LM...SMALL CRAFT ADVISORY UNTIL 3 PM CST THIS AFTERNOON FOR THE IL
AND IN NEARSHORE WATERS.
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