920  
FXUS63 KILX 221057  
AFDILX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE LINCOLN IL  
557 AM CDT SUN OCT 22 2017  
   
SHORT TERM
 
(TODAY AND TONIGHT)  
ISSUED AT 335 AM CDT SUN OCT 22 2017  
 
08Z/3AM SURFACE ANALYSIS SHOWS A SLOW-MOVING COLD FRONT  
APPROACHING THE MISSISSIPPI RIVER. MOST OF THE PRECIPITATION  
HAS BEEN OCCURRING ALONG AND JUST BEHIND THE FRONT...WITH VERY  
LITTLE FURTHER EAST INTO CENTRAL ILLINOIS. LATEST RADAR TRENDS ARE  
BEGINNING TO SHOW SHOWERS BECOMING MORE NUMEROUS AS FAR EAST AS  
THE ILLINOIS RIVER VALLEY: HOWEVER, THE BULK OF THE PRECIP REMAINS  
FURTHER WEST IN THE IMMEDIATE VICINITY OF THE BOUNDARY. WITH THE  
FRONT MOVING VERY SLOWLY EASTWARD AND INDIVIDUAL SHOWERS GENERALLY  
TRACKING N/NE, HAVE SLOWED THE ARRIVAL OF RAIN ACROSS THE KILX CWA  
THIS MORNING. BASED ON RADAR TRENDS, HAVE KEPT LOCATIONS NEAR THE  
INDIANA BORDER DRY UNTIL AROUND 14Z/9AM. MOST HIGH-RES MODELS SHOW  
SHOWERS SPREADING INTO THE AREA THIS MORNING IN A DIMINISHING  
STATE, THEN RE-DEVELOPING ACROSS THE EASTERN HALF OF THE AREA THIS  
AFTERNOON. END RESULT WILL BE A SHOWERY DAY, WITH PERHAPS A COUPLE  
RUMBLES OF THUNDER. HIGH TEMPERATURES WILL RANGE FROM THE LOWER  
60S NORTHWEST OF THE ILLINOIS RIVER...TO THE MIDDLE 70S IN THE  
WABASH RIVER VALLEY.  
 
AN UPPER WAVE CURRENTLY EVIDENT ON WATER VAPOR IMAGERY OVER THE  
OKLAHOMA/TEXAS PANHANDLES WILL TRACK EASTWARD AND EVENTUALLY CLOSE  
OFF ACROSS THE LOWER MISSISSIPPI RIVER VALLEY TONIGHT. AS IT DOES,  
IT WILL SLOW THE EASTWARD PROGRESSION OF THE COLD FRONT AND KEEP  
RAIN CHANCES ALIVE ACROSS MUCH OF THE AREA TONIGHT. WILL BRING THE  
SHOWERS TO AN END ALONG/WEST OF I-55 OVERNIGHT, BUT KEEP HIGH  
CHANCE TO LIKELY POPS IN THE FORECAST FURTHER EAST ACROSS THE  
REMAINDER OF THE AREA. LOW TEMPERATURES WILL RANGE FROM THE MIDDLE  
40S IN THE ILLINOIS RIVER VALLEY...TO THE MIDDLE 50S NEAR THE  
INDIANA BORDER.  
   
LONG TERM
 
(MONDAY THROUGH SATURDAY)  
ISSUED AT 335 AM CDT SUN OCT 22 2017  
 
SHOWERS WILL PERSIST ACROSS THE EASTERN KILX CWA THROUGH MONDAY AS  
SURFACE LOW PRESSURE TRACKS ALONG THE SLOW-MOVING BOUNDARY INTO  
THE OHIO RIVER VALLEY. ONCE THE LOW LIFTS FURTHER NORTHEAST, THE  
BEST RAIN CHANCES WILL DEPART: HOWEVER, WITH AN UPPER WAVE DIGGING  
SOUTHWARD INTO THE REGION ON TUESDAY, WIDELY SCATTERED SHOWERS AND  
MUCH COOLER WEATHER WILL BE ON TAP. WITH 850MB TEMPS PROGGED TO  
DROP TO AROUND -3C, HIGH TEMPERATURES WILL STRUGGLE TO REACH THE  
LOWER 50S ON TUESDAY. ANOTHER COOL FALL DAY IS EXPECTED ON  
WEDNESDAY BEFORE TEMPERATURES MAKE A TEMPORARY REBOUND BACK INTO  
THE MIDDLE TO UPPER 60S ON THURSDAY.  
 
AFTER THAT, A SIGNIFICANT COOLING TREND IS EXPECTED BY THE END OF  
THE WEEK: HOWEVER, MAJOR TIMING DIFFERENCES EXIST AMONG THE  
OPERATIONAL MODELS CONCERNING THE TIMING OF THE APPROACHING UPPER  
TROUGH RESPONSIBLE FOR THE COOLER CONDITIONS. THE 00Z OCT 22 GEM  
IS FASTER WITH THIS FEATURE, SHOWING A CLOSED UPPER LOW TRACKING  
NORTH OF CENTRAL ILLINOIS INTO THE GREAT LAKES BY SATURDAY  
MORNING. MEANWHILE, THE GFS AND ECMWF ARE CONSIDERABLY SLOWER,  
WITH THE ECMWF SHOWING THE CLOSED LOW MEANDERING EASTWARD INTO THE  
GREAT LAKES BY MONDAY. WITH SUCH A LARGE SPREAD IN MODEL  
SOLUTIONS, FORECAST CONFIDENCE BEYOND THURSDAY REMAINS POOR. AT  
THIS POINT, WILL CONTINUE TO FORECAST SHOWERS ON FRIDAY AS THE  
UPPER TROUGH AND ITS ASSOCIATED COLD FRONT APPROACH FROM THE WEST.  
BEYOND THAT, THE PRECIP FORECAST IS MURKY AT BEST...DEPENDING ON  
WHICH MODEL VERIFIES. WHAT IS CERTAIN HOWEVER, IS THAT TEMPS ARE  
GOING TO TAKE A NOSEDIVE AT SOME POINT THIS WEEKEND...SETTING THE  
STAGE FOR THE COLDEST WEATHER THUS FAR THIS FALL SEASON BY EARLY  
NEXT WEEK.  
 

 
   
AVIATION
 
(FOR THE 12Z TAFS THROUGH 12Z MONDAY MORNING)  
ISSUED AT 557 AM CDT SUN OCT 22 2017  
 
A COLD FRONT CURRENTLY JUST WEST OF THE ILLINOIS RIVER WILL SLOWLY  
PUSH EASTWARD TODAY...BRINGING SHOWERS AND MVFR CEILINGS TO THE  
CENTRAL ILLINOIS TERMINALS. LATEST OBS SHOW THE LOW CLOUDS  
ENCROACHING UPON KPIA, WITH SATELLITE TIMING TOOLS SUGGESTING THEY  
WILL BE THERE BY 12Z. BASED ON HRRR, HAVE INTRODUCED MVFR CEILINGS  
AT KSPI BY 14Z...THEN FURTHER EAST TO KCMI BY 16Z. THE FRONT WILL  
EVENTUALLY SLOW AND/OR STALL NEAR THE INDIANA BORDER THIS EVENING.  
AS A RESULT, CLOUD COVER WILL BE VERY SLOW TO CLEAR. IN FACT,  
LATEST MODELS SUGGEST KBMI/KDEC/KCMI MAY HOLD ON TO THEIR MVFR  
CEILINGS THROUGH THE REMAINDER OF THE 12Z TAF PERIOD. FURTHER  
WEST, HAVE RAISED CEILINGS TO VFR AT KPIA BY 22Z AND AT KSPI BY  
00Z.  
 

 
   
ILX WATCHES/WARNINGS/ADVISORIES
 
 
NONE.  

 
 

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