445  
FXUS63 KILX 010453  
AFDILX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE LINCOLN IL  
1153 PM CDT MON AUG 31 2015  
   
UPDATE
 
 
ISSUED AT 900 PM CDT MON AUG 31 2015  
 
SHOWERS HAVE ENDED THIS EVENING, WITH LINGERING PATCHES OF CLOUDS.  
FORECAST SOUNDINGS ARE POINTING TOWARD A RESIDUAL LAYER OF  
MOISTURE OVERNIGHT COULD LEAD TO SCATTERED CLOUDS FROM TIME TO  
TIME, BUT NOTHING SIGNIFICANT. OF MORE CONCERN WILL BE THE  
POTENTIAL FOR LOCALIZED DENSE FOG OVERNIGHT. DEWPOINTS REMAIN  
QUITE HIGH, IN THE UPPER 60S TO LOW 70S. WITH MOSTLY CLEAR SKIES  
AND LIGHT SOUTH WINDS OVER NIGHT, RADIATIONAL COOLING WILL HELP  
DEWPOINT SPREADS DECREASE TO 0-2 DEGREES AFTER MIDNIGHT. WE  
CONTINUED WITH FOG IN THE GRIDS FOR LATER TONIGHT INTO TOMORROW  
MORNING. OVERALL, THE CURRENT FORECAST HAS THE EXPECTED TRENDS  
COVERED WELL. NO FORMAL UPDATE WILL BE NEEDED THIS EVE.  
 

 
   
SHORT TERM
 
(TONIGHT)  
ISSUED AT 249 PM CDT MON AUG 31 2015  
 
WEAK REMNANTS OF A BOUNDARY DRAPED OVER THE SOUTH AND A SMALL SFC  
LOW OVER INDIANA ARE DOMINATING THE WEATHER THIS AFTERNOON FOR  
CENTRAL ILLINOIS. YESTERDAY THE 70 DEGREE DEWPOINTS WERE CONFINED  
TO RIGHT ALONG THE SFC BOUNDARY. TODAY, THEY ARE A LITTLE MORE  
WIDESPREAD, EVEN THIS LATE IN THE DAY AS MIXING OUT HAS BEEN LIMITED  
IN THE ALMOST STAGNANT AIRMASS. SOME OBS IN THE SOUTHEAST ARE  
ACTUALLY DROPPING INTO THE UPPER 60S AFTER SOME WEAK CONVECTIVE  
STORMS THIS MORNING. HOWEVER, QUITE LIKELY GOING TO SEE THOSE  
DEWPOINTS REBOUND QUICKLY DUE TO A LOT OF QPF/MOISTURE IN THE SOIL.  
WITH LIGHT SOUTHERLY WINDS AND VERY LITTLE IN THE WAY OF CLOUD COVER  
EXPECTED TONIGHT, FOG IS ONCE AGAIN THE BIGGEST CONCERN. WITH SOME  
MIXING STILL TO COME, HAVE LEFT THE FORECAST AS PATCHY FOR THE  
ENTIRE CWA TONIGHT.  
   
LONG TERM
 
(TUESDAY THROUGH MONDAY)  
ISSUED AT 249 PM CDT MON AUG 31 2015  
 
MAIN WEATHER STORY THROUGH THE EXTENDED REMAINS THE VERY WARM AND  
HUMID CONDITIONS THAT ARE EXPECTED TO PERSIST THROUGH THE WEEK AND  
INTO THE WEEKEND. HIGH TEMPERATURES ON TUESDAY WILL REACH THE UPPER  
80S TO AROUND 90 DEGREES...THEN READINGS WILL CLIMB INTO THE LOWER  
90S FOR THE REMAINDER OF THE PERIOD. DRY WEATHER WILL GENERALLY BE  
THE RULE...HOWEVER ISOLATED CONVECTION CANNOT BE RULED  
OUT...ESPECIALLY TUESDAY AFTERNOON AS A WEAKNESS IN THE MEAN 500MB  
RIDGE AXIS REMAINS IN THE VICINITY. MODELS CONTINUE TO SHOW SOME  
CONVECTION ACROSS THE EASTERN PARTS OF THE CWA AS THIS FEATURE  
GRADUALLY SHIFTS INTO THE GREAT LAKES BY WEDNESDAY.  
 
THE NEXT SIGNIFICANT CHANCE FOR RAIN WILL NOT ARRIVE UNTIL EARLY  
NEXT WEEK...WHEN A STRONG SHORT-WAVE FLATTENS THE UPPER RIDGE AND  
PUSHES A COLD FRONT INTO THE REGION. MODELS ARE IN DISAGREEMENT  
CONCERNING THE FRONT...WITH THE GFS NOW TRENDING SLOWER WITH THE  
COLD FRONT PASSING THROUGH CENTRAL ILLINOIS LATE MONDAY NIGHT INTO  
TUESDAY...WHILE THE ECMWF/GEM DOES NOT BRING THE COLD THROUGH THE  
CWA AT ALL AND KEEPS THE RIDGE STRONG OVER THE AREA. GIVEN  
PERSISTENT AND HIGHLY AMPLIFIED RIDGE POSITIONED ACROSS THE  
MIDWEST...THINK A SLOWER BREAK DOWN TO THE PATTERN IS STILL BEST  
SOLUTION. HAVE THEREFORE TRENDED SLOWER. AS A RESULT...AM  
EXPECTING DRY CONDITIONS THROUGH SUNDAY NIGHT...WITH RAIN CHANCES  
ARRIVING IN THE NORTHWEST MONDAY.  
 

 
   
AVIATION
 
(FOR THE 06Z TAFS THROUGH 06Z TUESDAY NIGHT)  
ISSUED AT 1153 PM CDT MON AUG 31 2015  
 
CLOUD COVER HAS NEARLY COMPLETELY DISSIPATED TOWARD 05Z, WITH NO  
APPRECIABLE FOG OF NOTE IN ANY LOCAL OBSERVATIONS, OTHER THAN CMI  
SHOWING 7SM AND DANVILLE 5SM BR. DEWPOINT DEPRESSIONS ARE RANGING  
FROM 8 DEG AT SPI TO 2 AT BMI, WITH DNV AT 1. AREAS OF MVFR FOG  
STILL APPEAR POSSIBLE, BUT HRRR HAS REDUCED THE AREAL COVERAGE OF  
IFR FOG TO JUST PATCHY AREAS IN EAST CENTRAL IL. HAVE ALTERED THE  
TEMPO GROUPS LATER TONIGHT TO BUMP UP VIS FROM 1 TO THE 3SM-4SM  
RANGE. FORECAST SOUNDINGS ARE NOT SUPPORTIVE OF SIGNIFICANT FOG  
LATER TONIGHT. THERE IS MORE SUPPORT FOR AREAS OF LOW CLOUDS TO  
BUBBLE UP AND DRIFT AROUND UNDER WEAK STEERING WINDS.  
 
AN UPPER LOW SPINNING OVER INDIANA WILL ONCE BE A FOCUS FOR SPOTTY  
SHOWERS AND ISOLATED THUNDERSTORMS TOMORROW, MAINLY SOUTHEAST OF  
CMI TO DEC. THE POTENTIAL FOR PRECIP AT OUR EASTERN TERMINALS IS  
LOW ENOUGH TO NOT INCLUDE ANY VCTS WITH THIS TAF ISSUANCE. WILL  
INCREASE VFR CLOUD COVER TO BKN040 AT CMI AND DEC.  
 
WINDS WILL CONTINUE OUT OF THE SOUTH THE REST OF THE NIGHT, WITH  
SPEEDS IN THE 5-7KT RANGE. AS WEAK HIGH PRESSURE SLIDES FARTHER  
EAST OF IL TOMORROW, WINDS WILL BECOME MORE SOUTHWEST AT 10KT OR  
LESS.  
 

 
   
ILX WATCHES/WARNINGS/ADVISORIES
 
 
NONE.  

 
 

 
 
UPDATE...SHIMON  
SHORT TERM...HJS  
LONG TERM...AUTEN  
AVIATION...SHIMON  
 
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