850  
FXUS63 KLOT 020506  
AFDLOT  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE CHICAGO/ROMEOVILLE, IL  
1106 PM CST THU DEC 1 2022  
   
SHORT TERM
 
 
ISSUED AT 326 PM CST THU DEC 1 2022  
 
THROUGH SATURDAY...  
 
KEY FORECAST MESSAGES THROUGH SATURDAY:  
*GUSTY WINDS FRIDAY THROUGH SATURDAY WITH GUSTS OF 40 TO 45 MPH  
EXPECTED.  
 
*CHANCE FOR LIGHT RAIN SHOWERS AND/OR DRIZZLE LATE FRIDAY AFTERNOON  
AND EVENING ALONG A COLD FRONT.  
 
*RAPIDLY COOLING TEMPERATURES FRIDAY NIGHT BEHIND THE FRONT.  
 
THE SURFACE HIGH THAT IS RESPONSIBLE FOR THE SUNNY SKIES TODAY  
CONTINUES TO MOVE EASTWARD INTO THE NORTHEAST THIS AFTERNOON AS A  
DEVELOPING SURFACE LOW MOVES INTO THE NORTHERN PLAINS AHEAD OF AN  
UPPER-LEVEL TROUGH THAT IS MOVING THROUGH THE PACIFIC NORTHWEST. THE  
SURFACE LOW IS EXPECTED TO CONTINUE TO DEEPEN AS IT MOVES INTO THE  
NORTHERN GREAT LAKES AND SOUTHERN CANADA THROUGH THE DAY ON FRIDAY  
WHICH WILL CREATE A TIGHTENING PRESSURE GRADIENT ACROSS NORTHEASTERN  
ILLINOIS AND NORTHWEST INDIANA AHEAD OF A COLD FRONT THAT WILL SWING  
THROUGH THE AREA FRIDAY EVENING. THIS WILL ALLOW GUSTY SOUTHERLY  
WINDS TO DEVELOP ACROSS THE AREA LATE TONIGHT AND LINGER INTO THE  
DAY ON SATURDAY WITH WIND GUSTS OF 30 TO 35 MPH ON FRIDAY BECOMING  
WESTERLY 40 TO 45 MPH FRIDAY NIGHT INTO SATURDAY MORNING BEHIND THE  
COLD FRONT. THERE CONTINUES TO BE SOME UNCERTAINTY IN EXACTLY HOW  
STRONG THE WINDS WILL BECOME ESPECIALLY IN THE WARM ADVECTION WING  
FRIDAY AFTERNOON, BUT IF THE ATMOSPHERE IS ABLE TO MIX AS FORECAST  
SOUNDINGS SUGGEST HIGHER GUSTS COULD CERTAINLY BE REALIZED DURING  
THE AFTERNOON AND EVENING HOURS. THE STRONGEST WINDS ARE EXPECTED TO  
ARRIVE BEHIND THE COLD FRONT AS STRONG COLD ADVECTION TAKES OVER AND  
ALLOWS THE ATMOSPHERE TO TAP INTO A STRONG LOW-LEVEL JET AND BRINGS  
40 TO 45 MPH GUSTS TO THE SURFACE. WHILE THESE WINDS ARE CLOSE TO  
WIND ADVISORY CRITERIA I DECIDED TO HOLD OFF ON A FORMAL ISSUANCE  
FOR NOW GIVEN THE LINGERING UNCERTAINTY AND TIME RANGE OF THE  
STRONGEST WINDS, BUT ONE MAY BE NEEDED WITH THE OVERNIGHT FORECAST  
UPDATE.  
 
IN ADDITION TO THE WINDS, THE COLD FRONT WILL ALSO BRING WITH IT THE  
CHANCE FOR LIGHT RAIN SHOWERS AND/OR DRIZZLE LATE FRIDAY AFTERNOON  
INTO THE EARLY PART OF SATURDAY MORNING. FORECAST SOUNDINGS CONTINUE  
TO SHOW THAT WHILE THE LOW-LEVELS ARE RATHER SATURATED THE MID-  
LEVELS ARE EXPECTED TO REMAIN DRY. THIS DRY AIR SHOULD LIMIT THE  
DEVELOPMENT OF MORE ROBUST PRECIPITATION AND KEEP ANY SHOWERS LIGHT  
AND CONFINED MOSTLY TO THE COLD FRONT. HOWEVER, SOME POCKETS OF  
DRIZZLE DO LOOK TO BE POSSIBLE LATE FRIDAY AFTERNOON AS SURFACE  
MOISTURE SURGES INTO THE REGION. PRECIPITATION CHANCES WILL COME TO  
AN END AS THE FRONT PASSES WITH MOST AREAS EXPECTED TO BE RAIN-FREE  
BY SATURDAY MORNING.  
 
LASTLY, TEMPERATURES WILL BE A ROLLER COASTER TO CLOSE OUT THE WEEK  
AND START THE WEEKEND. THE WARM ADVECTION AHEAD OF THE FRONT WILL  
ALLOW TEMPERATURES TO WARM INTO UPPER 40S AND LOWER 50S FRIDAY  
AFTERNOON AND EVENING, BUT ONCE THE FRONT PASSES THE STRONG COLD  
ADVECTION BEHIND IT WILL CAUSE TEMPERATURES TO PLUMMET HEADING INTO  
SATURDAY MORNING. LOWS ON SATURDAY MORNING ARE EXPECTED TO START OFF  
IN THE UPPER TEENS AND LOWER 20S WITH WIND CHILLS IN THE SINGLE  
DIGITS FOR MOST AREAS. HIGHS ON SATURDAY WILL ALSO BE COLD WITH  
TEMPERATURES STRUGGLING TO REACH FREEZING. DESPITE THE COLD  
TEMPERATURES SKIES WILL CLEAR OUT THROUGH THE DAY ON SATURDAY AS HIGH  
PRESSURE BUILDS BACK INTO THE AREA WITH WINDS GRADUALLY EASING  
THROUGH THE DAY AS WELL.  
 
YACK  
 

 
   
LONG TERM
 
 
ISSUED AT 252 PM CST THU DEC 1 2022  
 
SATURDAY NIGHT THROUGH THURSDAY...  
 
EXPANSIVE HIGH PRESSURE DRIFTING EASTWARD ALONG THE OHIO RIVER  
VALLEY WILL MAINTAIN DRY CONDITIONS THROUGH SUNDAY NIGHT AS SOME  
UPPER-LEVEL CIRRUS FILTER OVER THE AREA. WITH A RATHER DRY AIRMASS  
IN PLACE, A WEAKENING LOW-LEVEL TROUGH PASSING NORTH OF THE AREA  
WILL BRING ONLY BLUSTERY CONDITIONS WITH WSW GUSTS OVER 25 MPH ON  
SUNDAY AFTERNOON.  
 
BROAD SUB-TROPICAL RIDGING OVER THE GULF OF MEXICO AND A LONG-  
WAVE TROUGH OVER SOUTHERN CANADA WILL ENHANCE MID-LEVEL WESTERLIES  
EARLY NEXT WEEK AS SUBSTANTIAL BAROCLINICITY (40C N/S RANGE IN  
THE CENTRAL CONUS) DEVELOPS. PRECIP POTENTIAL IN THE FORECAST AREA  
WILL HINGE ON THE EXACT TIMING/STRENGTH OF ANY MID-LEVEL WAVES  
PROPOGATING THROUGH THE STRONG MID-LEVEL FLOW, WITH  
ENSEMBLE/DETERMINISTIC GUIDANCE VARIED ON THE TIMING OF ONE SUCH  
EMBEDDED WAVE SOMETIME LATE MONDAY INTO EARLY TUESDAY. LOW-LEVEL  
MOISTURE WILL REMAIN SUPPRESSED TO THE GULF COAST THROUGH SUNDAY,  
SO AMPLE MOISTURE RETURN THIS FAR NORTH WILL NOT OCCUR UNTIL AT  
LEAST LATE MONDAY OR EVEN TOWARD TUESDAY MORNING. FOR THAT REASON,  
ANY TROUGH PASSAGE MONDAY INTO MONDAY NIGHT WILL NEED TO TAP INTO  
LIMITED PACIFIC-SOURCED MID-LEVEL MOISTURE. PRIMARY PRECIP TYPE  
WITH ANYTHING MONDAY AFTERNOON WOULD BE LIGHT RAIN/SHOWERS, THOUGH  
WITH THE NOTED DEEP DRY AIRMASS, SNOW ALOFT WILL BE SUSCEPTIBLE  
TO COMPLETELY SUBLIMATING BEFORE REACHING THE MELTING LAYER.  
 
THE OVERALL COLUMN WILL GRADUALLY COOL INTO TUESDAY, WITH LOW  
WET- BULB ZERO HEIGHTS FAVORING PRIMARILY SNOW FOR ANY PRECIP. BUT  
WITH A VAST MAJORITY OF MODEL MEMBERS ALREADY ADVERTISING THE  
PASSAGE OF THE TROUGH BY THIS POINT, THE CURRENT FORECAST  
INDICATES ONLY A LOW CHANCE OF LIGHT SNOW.  
 
THE SUB-TROPICAL RIDGE WILL REMAIN ENTRENCHED OVER THE GULF OF  
MEXICO THROUGH THE REST OF THE WEEK, MAINTAINING STRONG MID-LEVEL  
WESTERLIES THAT FOSTER AN ACTIVE STORM TRACK SOUTH OF THE CWA.  
WITH OUR AIRMASSES ORIGINATING MORE FROM WESTERN CANADA THAN THE  
PACIFIC NORTHWEST DURING THIS TIME, TEMPS WILL LIKELY REMAIN  
SEASONABLE.  
 
KLUBER  
 

 
   
AVIATION
 
 
FOR THE 06Z TAFS...  
 
THE MAIN AVIATION WEATHER CONCERNS INCLUDE:  
 
* CONTINUED MARGINAL LLWS, MAINLY INVOF RFD TONIGHT  
 
* WINDS BECOMING INCREASINGLY GUSTY THROUGH FRIDAY, WITH CROSSWIND  
CHALLENGES FOR E-W RUNWAY OPERATIONS, ESPECIALLY LATER IN THE  
AFTERNOON  
 
* DEVELOPING MVFR CIGS FRIDAY AFTERNOON AND EVENING  
 
* BRIEF POTENTIAL FOR SHOWERS AND/OR DRIZZLE AHEAD OF AND  
IMMEDIATELY BEHIND AN ARCTIC COLD FRONT  
 
* VERY STRONG AND GUSTY WNW WINDS FRIDAY NIGHT  
 
SURFACE WINDS WILL REMAIN INTERMITTENTLY GUSTY OVERNIGHT, WITH A  
PERIOD OF LLWS CONTINUING MAINLY AT RFD UNDER THE CORE OF THE  
LOW-LEVEL JET. WIND SPEEDS AND GUSTS WILL CLIMB THROUGH THE DAY ON  
FRIDAY, WITH ROUTINE GUSTS TOWARDS 35 KTS BY THE MID TO LATE  
AFTERNOON. WINDS WILL FAVOR A 190-200 DIRECTION DURING THIS  
PERIOD, WHICH WILL RESULT IN SOME CROSSWIND CHALLENGES ON E-W  
RUNWAYS.  
 
DEEPER MOISTURE IS EXPECTED TO ARRIVE THROUGH FRIDAY EVENING, AND  
THIS MAY BE SUFFICIENT TO SQUEEZE OUT A PERIOD OF SHRA AND/OR DZ  
AS MVFR CIGS OVERSPREAD THE REGION. PROB30S HAVE BEEN MAINTAINED  
FOR THIS POTENTIAL. A POWERFUL COLD FRONT WILL ARRIVE AROUND 06Z  
AT THE CHICAGO-AREA SITES WITH A WNW WIND SHIFT AND SHARPLY-  
FALLING TEMPERATURES. WINDS LOOK TO GUST TOWARDS 40 KTS IN THE  
WAKE OF THE FRONT BEFORE EASING SOMEWHAT BY EARLY SATURDAY  
MORNING. AT THIS TIME, ALL PRECIPITATION IS EXPECTED TO END BEFORE  
SURFACE TEMPERATURES FALL BELOW FREEZING.  
 
CARLAW  
 

 
   
MARINE
 
 
ISSUED AT 326 PM CST THU DEC 1 2022  
 
ANOTHER QUICK-MOVING, DEEPENING LOW PRESSURE SYSTEM WILL CRUISE  
EAST ACROSS THE INTERNATIONAL BORDER FRIDAY INTO EARLY SATURDAY.  
THIS IS A VERY FAVORABLE SETUP FOR GALES, INCLUDING SOME HIGHER  
END GALE GUSTS (40 TO MAYBE 45 KT) IMMEDIATELY BEHIND THE COLD  
FRONT. THAT COLD FRONTAL TIMING FOR THE ILLINOIS AND INDIANA  
NEARSHORE WATERS IS NEAR OR SHORTLY AFTER MIDNIGHT FRIDAY NIGHT.  
SO THE PEAK WINDS WILL BE OVERNIGHT FRIDAY NIGHT INTO EARLY  
SATURDAY MORNING. AHEAD OF THE FRONT ON FRIDAY, SOUTHERLY WIND  
GUSTS WILL AT THE LEAST APPROACH GALES AND MAY FREQUENTLY GUST TO  
35 KT DEPENDING ON MAGNITUDE OF MIXING. AS FOR BEHIND THE PEAK  
GALES ON SATURDAY, WIND SPEEDS ON THE AFTERNOON LOOK TO COME DOWN  
QUICKLY WITH RESIDUAL WAVE ACTION LIMITED DUE TO THE WESTERLY  
COMPONENT OF THE WINDS. GIVEN THE CONTINUED CONFIDENCE IN GALE  
FORCE GUSTS THE GALE WATCH HAS BEEN UPDATED TO A GALE WARNING  
THROUGH SATURDAY MORNING.  
 
MTF/YACK  
 

 
   
LOT WATCHES/WARNINGS/ADVISORIES
 
 
IL...NONE.  
IN...NONE.  
LM...SMALL CRAFT ADVISORY...IL NEARSHORE WATERS UNTIL 3 PM FRIDAY.  
 
GALE WARNING...LMZ740-LMZ741-LMZ742...3 PM FRIDAY TO NOON  
SATURDAY.  
 
SMALL CRAFT ADVISORY...IN NEARSHORE WATERS UNTIL 9 AM FRIDAY.  
 
GALE WARNING...LMZ743-LMZ744-LMZ745...9 AM FRIDAY TO NOON  
SATURDAY.  
 

 
 

 
 
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