713  
FXUS63 KILX 172047  
AFDILX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE LINCOLN IL  
247 PM CST WED DEC 17 2014  
   
SHORT TERM
 
(TONIGHT)  
ISSUED AT 245 PM CST WED DEC 17 2014  
 
19Z/1PM SATELLITE IMAGERY CONTINUES TO SHOW OVERCAST CONDITIONS  
ACROSS MUCH OF CENTRAL ILLINOIS: HOWEVER, THE CLOUDS ARE BEGINNING  
TO ERODE NORTHWEST OF THE ILLINOIS RIVER. WHILE HRRR GUIDANCE HAS  
NOT BEEN PARTICULARLY USEFUL IN THE SHORT-TERM, SATELLITE TRENDS  
SUGGEST SKIES WILL PARTIALLY CLEAR ACROSS ALL BUT THE FAR E/NE KILX  
CWA BY EARLY EVENING. AFTER A PERIOD OF MOSTLY CLEAR SKIES EARLY  
TONIGHT, CLOUDS WILL ONCE AGAIN BEGIN INCREASING IN ADVANCE OF THE  
NEXT STORM SYSTEM, WHICH IS CURRENTLY EVIDENT ON WATER VAPOR IMAGERY  
OVER WEST TEXAS. QUITE A BIT OF PRECIP AND EVEN SOME THUNDER IS  
OCCURRING AHEAD OF THIS WAVE OVER OKLAHOMA/TEXAS: HOWEVER, IT IS  
EXPECTED TO WEAKEN AS IT LIFTS NORTHEASTWARD INTO THE REGION ON  
THURSDAY. IT WILL ALSO BE COMING INTO A DRY AIRMASS BENEATH A  
PREVAILING SURFACE RIDGE AXIS. FORECAST SOUNDINGS SHOW GRADUAL  
MOISTENING FROM THE TOP-DOWN LATER TONIGHT, BUT THE LOWEST LEVELS  
BELOW 850MB WILL REMAIN QUITE DRY THROUGH 12Z. AS A RESULT, HAVE  
MAINTAINED A DRY FORECAST THROUGH THE OVERNIGHT HOURS. DUE TO THE  
INITIALLY CLEAR SKIES AND LOW DEWPOINTS, HAVE GONE A COUPLE OF  
DEGREES BELOW MAV GUIDANCE FOR LOWS TONIGHT, WITH READINGS DROPPING  
INTO THE TEENS AND LOWER 20S.  
 

 
   
LONG TERM
 
(THURSDAY THROUGH WEDNESDAY)  
ISSUED AT 245 PM CST WED DEC 17 2014  
 
UPPER FLOW WILL BE ZONAL FOR NEXT FEW DAYS, WITH WEAK WAVES MOVING  
EAST THROUGH FLOW. MOISTURE CHANNEL DATA AND UPPER AIR SHOWS INITIAL  
WAVE TO AFFECT REGION OVER NM THIS MORNING. THIS SYSTEM TO  
CONTINUE TRACKING TO THE NORTHEAST, PUSHING SOME OVERRUNNING PCPN  
INTO MO AND SOUTHERN 1/2 OF IL FOR LATE TONIGHT INTO THURSDAY. WEAK  
VORT LOBE AND ISENTROPIC LIFT TO BE ENOUGH TO MOVE THE LIGHT SNOW  
INTO SOUTHERN 1/2 OF CWA IN THE MORNING, BUT WAVE MOVING FAST ENOUGH  
TO ONLY AFFECT THE MORNING. MAINLY LESS THAN HALF INCH.  
 
NEXT WAVE TO MOVE INTO REGION FOR FRIDAY NIGHT AND SATURDAY MORNING  
AND THE AREA OF LIFT WITH THIS ONE IS FARTHER SOUTH, MAINLY OVER  
SOUTHEAST CWA. AGAIN, SOME LIGHT SNOW POSSIBLE.  
 
UPPER FLOW STARTS TO CHANGE ON LATE IN WEEKEND AND BY MONDAY, FLOW  
IS NORTHWEST. DIGGING UPPER TROUGH OVER GREAT LAKES WITH UPPER LOW  
CLOSING OFF BY MONDAY NIGHT. THIS WILL BRING SOME INITIAL PCPN INTO  
THE REGION AHEAD OF COLD FRONT THAT MOVES THROUGH TUESDAY.  
TEMPERATURES HOWEVER, ARE ONLY COLD ENOUGH FOR POSSIBLE MIXTURE  
UNTIL POST FRONTAL ON TUESDAY NIGHT AND WEDNESDAY. THEREFORE NO SNOW  
ACCUMULATION. HOWEVER BY TUES NIGHT TO WED, ONLY MINOR VORT LOBES  
ROTATING AROUND THE CLOSED UPPER LOW IN THE COLD AIR, SO CHANCE OF  
LIGHT SNOW ACCUMULATIONS ONLY.  
 

 
   
AVIATION
 
(FOR THE 18Z TAFS THROUGH 18Z THURSDAY AFTERNOON)  
ISSUED AT 1203 PM CST WED DEC 17 2014  
 
MVFR CEILINGS WILL PREVAIL AT THE CENTRAL ILLINOIS TERMINALS FOR  
THE NEXT FEW HOURS BEFORE CLEARING GRADUALLY DEVELOPS FROM WEST TO  
EAST ACROSS THE AREA. 1730Z VISIBLE SATELLITE IMAGERY SHOWS  
CLEARING BEGINNING TO WORK INTO THE NORTHWEST KILX CWA AROUND  
GALESBURG, AND BASED ON TIMING TOOLS, THIS SHOULD REACH KPIA BY  
AROUND 21/22Z. WILL CONTINUE TO MONITOR SATELLITE TO SEE IF CLOUDS  
CAN ERODE FASTER, BUT FOR NOW WILL REMAIN PESSIMISTIC. CLOUDS WILL  
HOLD FIRM FURTHER EAST AT KCMI UNTIL EARLY EVENING WHEN FORECAST  
SOUNDINGS FINALLY SHOW LOW-LEVEL DRYING. AFTER A BRIEF PERIOD OF  
MOSTLY CLEAR SKIES TONIGHT, THE NEXT APPROACHING SYSTEM WILL  
SPREAD CLOUDS BACK INTO THE AREA ON THURSDAY. FORECAST SOUNDINGS  
SUGGEST VFR CEILINGS DEVELOPING ACROSS CENTRAL ILLINOIS BETWEEN 11Z  
AND 14Z. MAY SEE ENOUGH MOISTENING OF THE PROFILE TO PRODUCE LIGHT  
SNOW AT KSPI AFTER 15Z, BUT DRY CONDITIONS SHOULD PREVAIL  
ELSEWHERE.  
 

 
   
ILX WATCHES/WARNINGS/ADVISORIES
 
 
NONE.  

 
 

 
 
SHORT TERM...BARNES  
LONG TERM...GOETSCH  
AVIATION...BARNES  
 
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