076  
FXUS63 KLOT 090448  
AFDLOT  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL  
1148 PM CDT WED OCT 8 2025  
   
KEY MESSAGES  
 
- PATCHY FROST EXPECTED TONIGHT IN TYPICALLY COLDER, RURAL  
LOCATIONS, ESPECIALLY ACROSS NORTHWEST INDIANA.  
 
- A GROWING SIGNAL FOR SOME LIGHT RAIN ON FRIDAY, OTHERWISE  
GENERALLY DRY WITH SEASONABLE TEMPS THROUGH THE UPCOMING  
WEEKEND.  
 
 
   
UPDATE  
 
ISSUED AT 900 PM CDT WED OCT 8 2025  
 
NO SIGNIFICANT CHANGES TO THE FORECAST MADE THROUGH THURSDAY  
MORNING. A FROST ADVISORY REMAINS IN EFFECT FOR NORTHWEST IN  
FROM 3 AM UNTIL 8 AM CDT.  
 
HIGH PRESSURE OF 1032 MB REMAINS CENTERED OVER THE NORTHERN  
GREAT LAKES REGION AT MID-EVENING. THIS WILL MAINTAIN LIGHT  
NORTHEAST WINDS ACROSS THE AREA, ESPECIALLY NEAR LAKE MICHIGAN,  
OVERNIGHT. FARTHER INLAND HOWEVER, BETTER RADIATIONAL COOLING  
WILL RESULT IN STRONGER DECOUPLING OF THE BOUNDARY LAYER AND  
ALLOW WINDS TO BECOME LIGHT/VARIABLE/CALM. A DRY AIR MASS,  
LIGHT WINDS AND MAINLY CLEAR SKIES WILL SET THE STAGE FOR A  
CHILLY EARLY FALL NIGHT IN PORTIONS OF THE AREA. LIGHT, BUT  
PERSISTENT WINDS OFF OF LAKE MICHIGAN LOOK TO KEEP THINGS  
WARMER ACROSS MUCH OF THE CHICAGO METRO AND TO SOME EXTENT  
ACROSS NORTHERN IL, WHERE SLIGHTLY HIGHER DEW POINTS CONTINUE  
TO SPREAD WESTWARD. IN ADDITION, PATCHY LAKE-INDUCED STRATOCU IS  
EXPECTED TO INCREASE A BIT LATER TONIGHT NORTH OF CHICAGO  
PROPER. THIS, AND SLIGHTLY STRONGER WINDS ABOVE THE NOCTURNAL  
BOUNDARY LAYER INVERSION WILL ALSO HELP TO MODULATE STRONGER  
RADIATIONAL COOLING THERE.  
 
WHILE INTERIOR PARTS OF NORTHERN IL AWAY FROM THE CORE OF THE  
METRO WILL LIKELY SEE SOME MID-UPPER 30S FOR OVERNIGHT LOWS AND  
SOME PATCHY FROST IN SPOTS, NORTHWEST INDIANA AWAY FROM THE  
IMMEDIATE LAKE MICHIGAN SHORE APPEARS TO HAVE THE GREATEST  
POTENTIAL FOR MORE WIDESPREAD MID-30S OVERNIGHT LOWS AND  
GREATER FROST COVERAGE. THUS HAVE MAINTAINED THE CURRENT FROST  
ADVISORY HEADLINE FOR THAT AREA.  
 
OTHER THAN INCREASING PARTLY CLOUDY SKY COVER OVER FAR NORTHEAST  
IL NEAR THE LAKE LATER TONIGHT AND SOME HOURLY TEMP AND DEW  
POINT TWEAKS PER CURRENT OBSERVATION TRENDS, NO SIGNIFICANT  
CHANGES APPEAR WARRANTED AT THIS TIME.  
 
RATZER  
 
 
   
DISCUSSION  
 
ISSUED AT 250 PM CDT WED OCT 8 2025  
 
EARLY THIS AFTERNOON, A SCATTERED CUMULUS DECK IS BUILDING OFF  
THE LAKE AND EXTENDING SW ACROSS MUCH OF THE CWA, WHILE  
ELSEWHERE REMAINS MOSTLY SUNNY. TEMPERATURES ARE NEARING THEIR  
HIGHS FOR THE DAY IN THE LOWER AND MIDDLE 60S. LOCALIZED CLOUD  
COVER MAY CONTINUE TO DEVELOP OVER THE LAKE THROUGH THE NIGHT,  
BUT COVERAGE SHOULD BE LARGELY LIMITED TO COMMUNITIES NEAR THE  
IL LAKESHORE. A BIG MAJORITY OF OUR CWA WILL SEE MOSTLY CLEAR  
SKIES THROUGH THE NIGHT. SITTING COMFORTABLY WITHIN A BROAD  
SURFACE TROUGH, WINDS TONIGHT WILL ALSO BE LIGHT TO NEAR CALM  
WITH DRY BOUNDARY LAYER AIR. THIS IS A PRIME SETUP TO FAVOR THE  
COOLER SIDE OF GUIDANCE OVERNIGHT, WHICH WOULD RESULT IN LOWS IN  
THE MIDDLE TO UPPER 30S AROUND THE SUBURBS AND OUTLYING AREAS  
WHILE 40S ARE EXPECTED IN THE CITY AND AROUND THE INTERIOR METRO  
AREA. THE COOLEST CONDITIONS SHOULD LARGELY BE FOUND AROUND OUR  
NW INDIANA COUNTIES WHERE TEMPS MAY FALL TO JUST ABOVE  
FREEZING. SIMILAR CONDITIONS ARE EXPECTED ON MORE OF A LOCALIZED  
BASIS ACROSS RURAL AREAS OF NORTHERN IL. ACCORDINGLY, MADE THE  
DECISION TO HOIST A FROST ADVISORY FOR OUR FIVE INDIANA COUNTIES  
FROM 3AM/4AM TO 8AM/9AM CDT/EDT WHERE GREATER COVERAGE OF FROST  
IS ATTAINABLE AWAY FROM THE LAKE. FROST COVERAGE WILL BE MORE  
PATCHY ELSEWHERE AND PRIMARILY CONFINED TO OUTSIDE OF THE  
CHICAGO METRO.  
 
TOMORROW WILL BE VERY SIMILAR TO TODAY WITH HIGHS IN THE MIDDLE  
AND UPPER 60S BENEATH MOSTLY SUNNY SKIES. ATTENTION IN THE  
FORECAST THEN TURNS TO A TIGHTLY WOUND UPPER LOW THAT WILL CLIP  
THE REGION ON FRIDAY. THE LOW IS EXPECTED TO CLOSE UP NORTH OF  
THE GREAT LAKES LATE THURSDAY AND TRACK SOUTHEAST INTO THE THE  
UPPER OHIO VALLEY BY SATURDAY. THE STORM'S COLD FRONT WILL GET  
DRAGGED ACROSS THE CWA FRIDAY INTO FRIDAY NIGHT. ENSEMBLE POPS  
AROUND THE AREA HAVE BEEN ON A CONSISTENT UPWARD TREND RUN BY  
RUN, BUT PROBABILITIES FOR MEASURABLE PRECIP REMAIN CONSIDERABLY  
LOW, LARGELY IN THE 10 TO 30% RANGE. WITH THE COOLER MID LEVEL  
AIR STAYING OUT OF REACH TO OUR NORTH AND A DRY PBL ON FORECAST  
SOUNDINGS, INSTABILITY WILL BE LOW TO ABSENT. MOISTURE LOOKS  
RATHER SHALLOW AS WELL, BUT AMPLE ENOUGH TO STIR UP SOME LIGHT  
SHOWERS AMID SOME NOTEWORTHY OMEGA AHEAD OF THE ADVANCING LOW.  
THE NBM POPULATED THE FORECAST WITH ONLY SLIGHT CHANCES NEAR OUR  
NORTH, WHICH WAS MAINTAINED FOR NOW. THOSE MAY HAVE TO BE  
BUMPED UP OR EXPANDED THOUGH IN THE COMING DAYS, BUT BRIEF AND  
LIKELY LIGHTER SHOWERS ARE PROBABLY ALL WE'RE LOOKING AT FOR  
FRIDAY.  
 
FRIDAY COULD ALSO FEATURE A GOOD BREEZE, ESPECIALLY IN OUR  
NORTH AND NORTHWEST, AS WE MIX INTO A DECENT LLJ. THERE IS  
SUPPORT FOR 20 TO EVEN NEAR 30 MPH GUSTS, BUT THERE IS STILL  
SOME UNCERTAINTY. FOR NOW, BOOSTED THE FORECAST FROM THE NBM TO  
GET SOME NEAR 20 MPH GUSTS UP THAT WAY, BUT THESE MAY NEED TO BE  
BUMPED EVEN FURTHER AS CONFIDENCE GROWS. IF THE RAIN HOLDS OUT  
AND WINDS PERFORM TO THEIR FULLEST, A LOCALIZED ELEVATED FIRE  
RISK MAY EVEN BE IN THE CARDS IN OUR WEST AND NORTHWEST ON  
FRIDAY.  
 
FOR THE PAST COUPLE OF DAYS NOW, MEDIUM RANGE DETERMINISTIC AND  
ENSEMBLE GUIDANCE HAS BEEN TRENDING COOLER BEHIND THE FRONT ON  
FRIDAY WHICH MAY HAVE IMPLICATIONS FOR TEMPERATURES THIS WEEKEND.  
FORECAST HIGHS FOR SATURDAY AND SUNDAY HAVE BEEN ON A STEADY  
DOWNWARD TREND. WHILE THERE STILL IS SOME UNCERTAINTY AND  
SUPPORT FOR WARMER CONDITIONS, HIGHS IN THE 60S AROUND THE METRO  
ARE LOOKING MORE LIKELY WITH TIME, ESPECIALLY ON SATURDAY.  
LOWER 70S MAY BE MORE ATTAINABLE ACROSS OUTLYING AREAS. SUNDAY  
SHOULD BE A TAD WARMER WITH SOME SOUTHERLY RETURN FLOW KICKING  
IN LATE SATURDAY. FOR SUNDAY THE FORECAST IS NOW CALLING FOR 50S  
DOWNTOWN THROUGH MID- MORNING AND PEAKING IN THE MIDDLE 60S.  
 
MORE UNCERTAINTY LINGERS INTO NEXT WEEK, BUT SLIGHTLY WARMER-  
THAN-AVERAGE CONDITIONS ARE FAVORED FOR AT LEAST THE FIRST HALF  
OF THE WEEK. ANOTHER, MUCH LARGER SYNOPTIC SYSTEM LOOKS TO CLIP  
THE REGION EARLY NEXT WEEK INTRODUCING SLIGHTLY HIGHER PRECIP  
CHANCES TO THE FORECAST, BUT THERE REMAINS NO SOLID SIGNAL FOR A  
HEALTHY WIDESPREAD RAIN OVER THE NEXT SEVEN DAYS.  
 
DOOM  
 
 
   
AVIATION /06Z TAFS THROUGH 12Z FRIDAY/  
 
ISSUED AT 1148 PM CDT WED OCT 8 2025  
 
THERE COULD BE SOME LAKE EFFECT STRATOCUMULUS INTO ORD AND MDW  
THIS THROUGH EARLY MORNING. CAN'T TOTALLY RULE OUT A BRIEF LOW  
END VFR OR HIGH END MVFR CIG, ESPECIALLY AT ORD, OTHERWISE LOOK  
FOR GENERALLY CLEAR SKIES THROUGH THE TAF CYCLE. WINDS WILL  
REMAIN AT OR BELOW 10KT FROM MOSTLY AN EASTERLY DIRECTION.  
 
- IZZI  
 
 
   
LOT WATCHES/WARNINGS/ADVISORIES  
 
IL...NONE.  
IN...FROST ADVISORY FROM 3 AM CDT /4 AM EDT/ TO 8 AM CDT /9 AM EDT/  
THURSDAY FOR INZ001-INZ002-INZ010-INZ011-INZ019.  
 
LM...NONE.  
 
 
 
 
 
VISIT US AT WEATHER.GOV/CHICAGO  
CLICK HERE TO GO TO PREVIOUS BULLETINS.
The Nexlab IL Page
The Nexlab IN Page
Main Text Page