681  
FXUS63 KLOT 170449  
AFDLOT  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL  
1049 PM CST SAT NOV 16 2024  
   
KEY MESSAGES
 
 
- PERIODS OF RAIN ARE EXPECTED MONDAY THROUGH TUESDAY MORNING.  
 
- ANOTHER SYSTEM WILL MOVE IN WEDNESDAY THROUGH THURSDAY WITH  
ADDITIONAL CHANCES FOR PRECIPITATION.  
 
- A COLDER AIR MASS WILL SETTLE IN LATE NEXT WEEK WITH MORNING  
LOW TEMPERATURES AT OR BELOW FREEZING.  
 

 
   
UPDATE
 
 
ISSUED AT 914 PM CST SAT NOV 16 2024  
 
A BROAD SHORTWAVE TROUGH AND ITS ASSOCIATED SURFACE LOW CONTINUE  
TO TRAVERSE ACROSS THE NORTHERN PLAINS THIS EVENING WITH THE  
SYSTEMS OCCLUDING FRONTAL BOUNDARY STRETCHING FROM CENTRAL MN  
SOUTHWESTWARD INTO IA AND EASTERN NE. AHEAD OF THE FRONT, A BAND  
OF SHOWERS HAS DEVELOPED ON THE NOSE OF A PLUME OF ELEVATED  
INSTABILITY AND CONTINUES TO TRACK EAST TOWARDS NORTHERN IL.  
DESPITE THE ROBUST LOOK ON RADAR, RECENT SURFACE OBSERVATIONS  
SHOW THAT THE MAJORITY OF THESE SHOWERS ARE NOT REACHING THE  
GROUND. SINCE MOISTURE IN THE SUB-CLOUD LAYER IS NOT EXPECTED TO  
IMPROVE MUCH OVERNIGHT, SUSPECT THAT SHOWERS WILL STRUGGLE TO BE  
MUCH MORE THAN SPRINKLES AS THEY PASS OVERHEAD TONIGHT.  
 
HOWEVER, MOSTLY TO COMPLETELY CLOUDY SKIES ARE EXPECTED TONIGHT  
AS THE SHOWERS/SPRINKLES PASS. THUS TEMPERATURES ARE NOT  
EXPECTED TO CHANGE MUCH FROM THEIR CURRENT READINGS WITH  
OVERNIGHT LOWS IN THE LOW TO MID-40S (UPPER 40S IN CHICAGO)  
FORECAST. WINDS ON THE OTHER HAND WILL REMAIN ELEVATED TONIGHT  
WITH OCCASIONAL GUSTS IN THE 15-20 MPH RANGE OUT OF THE  
SOUTH-SOUTHEAST.  
 
AS FOR SUNDAY, THE SHOWERS/SPRINKLES TONIGHT WILL EXIT THE AREA  
BY MID-MORNING LEAVING US WITH MOSTLY DRY CONDITIONS OTHERWISE.  
THOUGH, CONFIDENCE IS INCREASING THAT ADDITIONAL SHOWERS MAY  
DEVELOP SUNDAY AFTERNOON AS THE AFOREMENTIONED FRONT PIVOTS  
THROUGH NORTHERN IL AND INTERACTS WITH A STRONG JET STREAK AND  
ASSOCIATED VORT MAX. GIVEN THAT THE COVERAGE OF SHOWERS SUNDAY  
AFTERNOON REMAINS LOWER CONFIDENCE DUE TO AVAILABLE MOISTURE,  
HAVE DECIDED TO INTRODUCE ONLY SLIGHT CHANCE (AROUND 20%) POPS  
TO THE FORECAST FOR NOW. IF THIS TREND CONTINUES WOULD NOT  
BE SURPRISED IF HIGHER POPS ARE INTRODUCED BY INCOMING MIDNIGHT  
SHIFT. REGARDLESS, TEMPERATURES ARE STILL EXPECTED TO BE ABOVE  
NORMAL FOR MID-NOVEMBER WITH HIGHS AROUND 60 DEGREES.  
 
YACK  
 

 
   
DISCUSSION
 
 
ISSUED AT 154 PM CST SAT NOV 16 2024  
 
THROUGH SUNDAY NIGHT:  
 
A WEAKENING COLD FRONT WILL MOVE ACROSS THE AREA SUNDAY MORNING  
AND THEN LIKELY STALL ACROSS CENTRAL IL AND CENTRAL IN SUNDAY  
NIGHT. THE GRADIENT WILL SUPPORT SOUTHERLY WINDS GUSTING INTO  
THE 25 MPH TO PERHAPS 30 MPH RANGE TONIGHT. WINDS WILL TURN  
MORE SOUTHWESTERLY SUNDAY MORNING AND REMAIN GUSTY.  
 
THERE WILL ALSO BE A LOW CHANCE OF SHOWERS AHEAD OF THE FRONT  
OVERNIGHT INTO SUNDAY MORNING. WITH SOMEWHAT DRIER LOW LEVELS,  
ABOVE THE STRATUS, ITS POSSIBLE THERE COULD BE QUITE A BIT OF  
VIRGA AND SOME SPRINKLES. BUT A FEW SHOWERS REMAIN POSSIBLE AND  
NO CHANGES TO SLIGHT CHANCE POPS. THERE IS SOME UNCERTAINTY FOR  
TIMING/LOCATION WITH A CONTINUED CHANCE ACROSS NORTHERN IL  
SUNDAY AFTERNOON. DESPITE THE LOW CHANCES, SOME FURTHER  
REFINEMENT WITH THE POPS IS LIKELY WITH LATER FORECASTS.  
 
SOME BREAKS IN THE CLOUDS HAVE DEVELOPED EARLY THIS AFTERNOON  
ALONG WITH SLOW BUT STEADY CLEARING FROM THE SOUTHEAST ACROSS  
WEST CENTRAL IN. SOME PARTIAL CLEARING IS POSSIBLE INTO THIS  
EVENING BUT OVERALL TRENDS STILL SUPPORT MOSTLY CLOUDY TONIGHT  
AND INTO SUNDAY. SHOULD ANY CLEARING REMAIN PREVAILING TONIGHT,  
THAT MAY ALLOW TEMPS TO DROP BELOW THE CURRENT FORECAST LOWS  
WHICH ARE IN THE LOWER/MID 40S. HIGHS ON SUNDAY MAY DEPEND ON  
CLOUD TRENDS WITH MOST AREAS LIKELY REACHING THE UPPER 50S AND  
POSSIBLY AROUND 60. WITH SOME CLEARING EXPECTED SUNDAY NIGHT,  
ESPECIALLY ACROSS THE NORTH, LOWS MAY DROP IN THE 30S ACROSS THE  
NORTHWEST CWA. CMS  
 
MONDAY THROUGH SATURDAY:  
 
A LONG WAVE UPPER LEVEL TROUGH WILL BE SITUATED OVER THE  
PACIFIC NORTHWEST ON MONDAY AND MOVE EASTWARD THROUGH THE MIDDLE  
OF THE WEEK. OUT AHEAD OF IT, THERE WILL BE A SHORTER,  
NEGATIVELY TILTED WAVE OVER NORTHERN MEXICO THAT WILL MOVE  
NORTHEASTWARD TOWARD MINNESOTA MONDAY INTO TUESDAY MORNING.  
MODELS ARE SUGGESTING THAT THE LEADING SHORT WAVE WILL WEAKEN  
AND PHASE WITH THE LONGER WAVE IN THE MIDDLE OF THE WEEK, BEFORE  
THE LONGER WAVE TROUGH STRENGTHENS AND FORMS A CLOSED LOW OVER  
THE NORTHERN PLAINS THAT WILL MOVE EASTWARD THROUGH THE END OF  
THE WEEK.  
 
ASSOCIATED WITH THESE WAVES, WILL BE TWO WEATHER SYSTEMS THAT  
WILL IMPACT NORTHERN ILLINOIS AND NORTHWEST INDIANA. THE FIRST  
ON MONDAY INTO TUESDAY MORNING. AS A SURFACE LOW MOVES  
NORTHEASTWARD THROUGH THE GREAT PLAINS MONDAY, A WARM FRONT WILL  
MOVE OVER THE AREA PROVIDING ENOUGH FORCING TO INDUCE SHOWERS  
FROM SOUTH TO NORTH THROUGH THE AFTERNOON. THE LOW IS PROJECTED  
TO SLOWLY OCCLUDE AND WEAKEN THROUGH THE NIGHT, BUT NOT BEFORE  
PUSHING A SECONDARY FRONT ACROSS THE AREA PROVIDING WIDESPREAD  
RAIN MONDAY EVENING AND INTO TUESDAY MORNING. WINDS WILL BECOME  
BREEZY TO AROUND 25 MPH OUT OF THE EAST TO SOUTHEAST AS THIS  
SYSTEM APPROACHES, PARTICULARLY IN THE EVENING TIME FRAME AS THE  
LOW LEVEL JET RAMPS UP. RAIN WILL SLOWLY TAPER OFF FROM  
SOUTHWEST TO NORTHEAST THROUGH THE MORNING ON TUESDAY.  
TEMPERATURES ARE EXPECTED TO REACH INTO THE LOW 60S IN THE  
AFTERNOON, WITH DRIER CONDITIONS ON TUESDAY AHEAD OF THE NEXT  
SYSTEM.  
 
THERE HAS BEEN FAIRLY GOOD AGREEMENT AMONG MODELS ON THE RAIN  
CHANCES FOR MONDAY/TUESDAY. HOWEVER, THAT CANNOT BE SAID ABOUT  
THE SECOND SYSTEM LIKELY IMPACTING THE REGION BETWEEN WEDNESDAY  
AND THURSDAY. MODELS HAVE STRUGGLED TO AGREE ON TIMING AND  
LOCATION AS THIS SYSTEM MOVES EAST. IT RESULTS IN IMPACTING  
CONFIDENCE IN THE FORECAST, ESPECIALLY WITH THE COLDER AIRMASS  
MOVING IN BEHIND IT WHICH COULD INFLUENCE THE TYPE OF  
PRECIPITATION.  
 
AS THE UPPER LEVEL LONG WAVE MOVES EAST, A STRONG JET STREAK  
WILL MOVE OVER THE MIDWEST AS A NEW SURFACE LOW DEVELOPS WEST OF  
THE MISSISSIPPI RIVER. AS THE LOW MOVES TO THE NORTHEAST,  
MODELS HAVE BEEN SUGGESTING IT WILL PINWHEEL AROUND WEDNESDAY  
INTO THURSDAY BEFORE FINALLY DEPARTING TO THE EAST INTO FRIDAY.  
THE LATEST GFS HAS THE LOW FORMING OVER CENTRAL OHIO AND  
SPINNING OVER BUFFALO, WHILE THE EURO HAS IT FORMING OVER  
INDIANA AND ENCIRCLING AROUND DETROIT WITH A DEEPER MINIMUM  
PRESSURE. THE CONTINUED SIGNAL OF A SYSTEM MOVING THROUGH MID  
WEEK KEEPS THE CHANCES FOR PRECIPITATION IN THE FORECAST;  
HOWEVER, THE LACK OF AGREEMENT IN MODELS LOWERS CONFIDENCE IN  
THE DETAILS OF WHAT IS AND WILL BE A COMPLEX SYSTEM.  
TEMPERATURES ON WEDNESDAY SHOULD BE WARM ENOUGH TO SUPPORT  
MAINLY RAIN FOR ANY SHOWERS THAT WOULD DEVELOP. DESPITE SURFACE  
TEMPERATURES STAYING ABOVE 32F, 850 MB TEMPERATURES ON THE BACK  
SIDE OF THE WAVE ARE EXPECTED TO PLUMMET BELOW FREEZING LEADING  
TO THE POTENTIAL FOR THE FIRST SNOWFLAKES OF THE SEASON MIXED IN  
WITH THE RAIN. BETTER CHANCES FOR SNOW WOULD LEAN TOWARD THE  
MORE WESTERN SOLUTION OF THE EURO, AS OPPOSED TO THE GFS  
SOLUTION BEING FARTHER TO THE EAST. FOR NOW, THE FORECAST  
MAINTAINED JUST A SLIGHT CHANCE (15 PERCENT) FOR WET SNOW TO BE  
MIXED IN FOR AREAS MAINLY SOUTH OF I-88 AND AWAY FROM LAKE  
MICHIGAN, UNTIL MODELS (HOPEFULLY) COME INTO BETTER AGREEMENT.  
 
THE OTHER IMPACT TO THE UNCERTAINTY ON THE STRENGTH AND  
LOCATION OF THE LOW WILL BE TO THE WIND FORECAST. WINDS ARE  
EXPECTED TO INCREASE ON THE BACKSIDE OF THE LOW AS IT MOVES  
EAST OF THE REGION. WHILE THE FORECAST DEPICTS STRONGER WINDS  
DEVELOPING, THERE COULD BE THE POTENTIAL TO INCREASE GUSTS  
HIGHER DEPENDING ON IF CONFIDENCE INCREASES ON THE PLACEMENT OF  
THE LOW.  
 
CHANCES FOR PRECIPITATION DIMINISH AFTER THURSDAY AS THE SYSTEM  
EVENTUALLY MOVES TO THE EAST OF THE AREA. THE EXCEPTION WAS TO  
KEEP SLIGHT CHANCE TO CHANCE POPS (15 TO 35 PERCENT) AROUND LAKE  
MICHIGAN DUE TO THE PREVAILING NORTHWEST FLOW THAT COULD  
POTENTIALLY LEAD TO SOME LAKE EFFECT PRECIP INTO THE WEEKEND.  
TEMPERATURES ARE EXPECTED TO DROP IN THE WAKE OF THIS SYSTEM  
WITH HIGH TEMPERATURES THURSDAY THROUGH SATURDAY IN THE 40S WITH  
OVERNIGHT LOWS FRIDAY AND SATURDAY MORNING AT OR BELOW  
BREEZING.  
 
DK  
 

 
   
AVIATION /06Z TAFS THROUGH 12Z MONDAY/
 
 
ISSUED AT 1048 PM CST SAT NOV 16 2024  
 
THE MAIN AVIATION WEATHER ITEMS ARE:  
 
* SMALL CHANCES FOR INTERMITTENT SPRINKLES OVERNIGHT  
 
* WINDS BECOME SOUTHWESTERLY TONIGHT INTO SUNDAY MORNING  
 
* POTENTIAL (20-30 PERCENT) FOR LIGHT SHOWERS SUNDAY AFTERNOON  
AND EARLY EVENING  
 
SOUTH-SOUTHEASTERLY WINDS WILL BECOME SOUTH-SOUTHWESTERLY  
OVERNIGHT, WITH INTERMITTENT GUSTS TO AROUND 20 KNOTS AT  
ORD/MDW. A FEW SPRINKLES CAN'T BE RULED OUT, BUT CHANCES ARE TOO  
LOW FOR A MENTION IN THE TAFS.  
 
VFR CONDITIONS ARE EXPECTED ON SUNDAY. A BRIEF POTENTIAL FOR  
LIGHT SHOWERS EXISTS SUNDAY AFTERNOON AND EVENING. HAVE  
INTRODUCED A PROB30 AT RFD TO ACCOUNT FOR THIS. AT THIS TIME,  
CHANCES APPEAR A LITTLE LOWER AT THE CHICAGO-AREA TERMINALS, AND  
HAVE REFRAINED FROM A MENTION IN THE LATEST TAFS.  
 
WINDS WILL TURN NORTHWESTERLY SUNDAY EVENING, BUT WILL BE FAIRLY  
LIGHT. SOME FOG POTENTIAL EXISTS, MAINLY AT RFD SUNDAY NIGHT,  
BUT THIS POTENTIAL WILL BE ADDRESSED IN FUTURE TAF ISSUANCES.  
 
CARLAW  
 

 
   
LOT WATCHES/WARNINGS/ADVISORIES
 
 
IL...NONE.  
IN...NONE.  
LM...SMALL CRAFT ADVISORY UNTIL 3 AM CST SUNDAY FOR WINTHROP HARBOR  
TO NORTHERLY IS. IL.  
 

 
 

 
 
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