373  
FXUS63 KILX 180441  
AFDILX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE LINCOLN IL  
1141 PM CDT WED SEP 17 2014  
   
UPDATE
 
 
ISSUED AT 854 PM CDT WED SEP 17 2014  
 
SHOWERS AND THUNDERSTORMS OVER SE/E-CENTRAL IL THIS  
AFTERNOON/EARLY EVENING HAVE ENDED AS THE SHORTWAVE FEATURE  
RESPONSIBLE THEM HAS MOVED EAST OF THE AREA. SENT UPDATES EARLIER  
TO ACCOUNT FOR THE FEATURE AND REMAINDER OF THE NIGHT IS DRY IN  
CURRENT FORECAST. HIGH PRESSURE CENTERED JUST NORTH OF LAKE  
SUPERIOR WILL PUSH DRIER AIR INTO CENTRAL ILLINOIS FROM THE  
NORTHEAST ALONG WITH LIGHT NORTHEAST WINDS OVERNIGHT. THIS SHOULD  
HELP LIMIT FOG FORMATION OVERNIGHT MOST AREAS...HOWEVER HIGHER  
DEWPOINTS MAINLY SOUTH OF I-70 AS A RESULT OF THE EARLY EVENING  
RAIN WILL LIKELY PROVIDE ENOUGH MOISTURE FOR FOG. HAVE SENT  
UPDATES FOG OVERNIGHT.  
 

 
   
SHORT TERM
 
(TONIGHT)  
ISSUED AT 234 PM CDT WED SEP 17 2014  
 
A SMALL MCS OVER SOUTHERN MO INTO FAR NORTHERN AR ASSOCIATED WITH A  
VORT MAX WITH THE SHORT WAVE TRACKING ESE INTO MID MS RIVER VALLEY  
INTO THIS EVENING AND STAYING SOUTH OF THE FORECAST AREA. HOWEVER  
SOME WEAK ISENTROPIC LIFT ON NORTHERN FRINGE OF SYSTEM AFFECTING OUR  
SW COUNTIES INTO MID AFTERNOON WITH ISOLATED SHOWERS AND EVEN ONE  
OR TWO THUNDERSTORMS. THE MODELS SHOW THIS ISENTROPIC LIFT  
DIMINISHING LATER THIS AFTERNOON AND EARLY EVENING AS IT SHIFTS  
SOUTHWARD, SO GOING TO KEEP A DRY FORECAST TONIGHT. BROKEN TO  
OVERCAST MID LEVEL CLOUDS SHOULD ALSO DECREASE FROM THE NORTH WHILE  
SCATTERED TO BROKEN CUMULUS CLOUDS OF 4-6K FT ALSO DISSIPATE LATE  
TODAY. WEAK HIGH PRESSURE OF 1018 MB OVER CENTRAL IN AND SOUTHEAST  
IL WILL WEAKEN AS A STRONGER 1024 MB CANADIAN HIGH PRESSURE OVER  
MANITOBA SETTLES SSE INTO THE UPPER GREAT LAKES BY THU MORNING. THIS  
WILL PROVIDE THE FAIR WEATHER TONIGHT INTO THU ALONG WITH TURNING  
SSE WINDS MORE ENE AND STAYING FAIRLY LIGHT. WITH SOME DRIER AIR  
ADVECTING IN FROM THE NE, DO NOT THINK FOG WILL BE AS PREVALENT  
OVERNIGHT WHERE WE HAD WIDESPREAD DENSE FOG IN SOUTHEAST IL, BUT CAN  
NOT RULE OUT A FEW PATCHES OF SHALLOW GROUND FOG OVER SOUTHERN AND  
WESTERN AREAS WHERE DEWPOINTS WILL BE A FEW DEGREES HIGHER AND ALSO  
HAD SOME LIGHT RAIN SW OF LINCOLN TODAY ALONG WITH EXTENSIVE CLOUD  
COVER. LOWS IN THE UPPER 40S AND LOWER 50S WITH COOLEST READINGS  
FROM LINCOLN NORTHEAST.  
 

 
   
LONG TERM
 
(THURSDAY THROUGH WEDNESDAY)  
ISSUED AT 234 PM CDT WED SEP 17 2014  
 
WEAK LOW-LEVEL COLD ADVECTION BEHIND SHORTWAVE MOVING THROUGH THE  
AREA TODAY WILL KEEP TEMPS FROM WARMING MUCH COMPARED TO TODAY'S  
HIGHS DESPITE MORE SUNSHINE AND INCREASING 500MB HEIGHTS. BY FRIDAY  
AFTERNOON 850MB TEMPS RESPOND TO THE BUILDING RIDGE AND BEGIN TO  
CLIMB BACK TOWARD SEASONAL NORMALS.  
 
RIDGE BEGINS TO FLATTEN AS WEEKEND APPROACHES. MID-LEVEL HEIGHTS  
BUILD OVER WESTERN NORTH AMERICA. ENERGY NOW OFF WEST COAST IS  
EXPECTED TO SPLIT INTO A WEAK CUTOFF ALONG THE CALIFORNIA COAST AND  
A SERIES OF SHORTWAVES TOPPING THE DEVELOPING WESTERN NORTH AMERICA  
RIDGE. ALTHOUGH THE PATTERN SHIFT IS SIMILAR BETWEEN THE OPERATIONAL  
MODELS AND NAEFS MEAN, THE RELATIVE STRENGTH OF THE INDIVIDUAL  
SHORTWAVES HAVE IMPLICATIONS ON THE TIMING OF PRECIP CHANCES THROUGH  
THE WEEKEND. LATEST ECMWF IS WEAKER WITH INITIAL WAVE EXPECTED TO  
MOVE ACROSS THE AREA SATURDAY AFTERNOON, WHILE 17/12Z GFS IS STRONG  
ENOUGH TO PRODUCE SUFFICIENT LIFT AND COLD ADVECTION ALOFT FOR THE  
DEVELOPMENT OF THUNDERSTORMS. 17/00Z IS WEAKER WITH THIS INITIAL  
WAVE AND PRODUCES MORE SPOTTY PRECIP.  
 
DESPITE INCREASING CLOUDS, BREEZY SOUTH TO SOUTHWEST WINDS WILL  
ALLOW TEMPS TO CLIMB INTO THE 80S SATURDAY AS MODELS ARE CONSISTENT  
IN ENABLING 850MB TEMPS TO REACH 16-18C BY 12Z.  
 
CLOUDS MAY HAVE A HARD TIME CLEARING ON SUNDAY AND EVEN SOME PRECIP  
IS POSSIBLE DURING THE DAY IN SOUTHEAST ILLINOIS AS SECOND WAVE IN  
THE TROUGH MOVES ACROSS THE AREA. LOW-LEVEL COLD ADVECTION KICKS IN  
SUNDAY NIGHT FOLLOWING THIS SECOND WAVE, BUT MID-LEVEL HEIGHTS BEGIN  
CLIMBING AGAIN BY MONDAY NIGHT. ALTHOUGH, TEMPS WILL LIKELY BE BELOW  
NORMAL THROUGH MIDWEEK, THE MODELS NO LONGER REFLECT THE VERY COLD  
TEMPERATURES THAT WERE PROGGED BY THE EMCWF SEVERAL DAYS AGO.  
 

 
   
AVIATION
 
(FOR THE 06Z TAFS THROUGH 06Z THURSDAY NIGHT)  
ISSUED AT 1141 PM CDT WED SEP 17 2014  
 
SCT/BKN MID LEVEL CLOUDS REMAIN OVER EAST-CENTRAL IL AND WILL  
CONTINUE TO SHIFT EASTWARD AND DISSIPATE OVENIGHT. HIGH PRESSURE  
JUST NORTH OF THE GREAT LAKES WILL BRING LIGHT E/NE FLOW  
FOR THE NEXT 24 H, WITH WIND SPEEDS GENERALLY 4-7 KTS. FOG  
POSSIBLE OVERNIGHT...MAINLY SOUTH OF KSPI-KMTO. GENERALLY VFR-MVFR  
CONDITIONS, HOWEVER LOCALLY LIFR/VLIFR POSSIBLE. MOSTLY CLEAR  
SKIES FOR THE DAYTIME HOURS WITH ONLY SOME DIURNAL CU.  
 

 
   
ILX WATCHES/WARNINGS/ADVISORIES
 
 
NONE.  

 
 

 
 
UPDATE...ONTON  
SHORT TERM...07  
LONG TERM...BARKER  
AVIATION...ONTON  
 
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