696  
FXUS63 KILX 290154  
AFDILX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE LINCOLN IL  
854 PM CDT FRI APR 28 2017  
   
UPDATE
 
 
ISSUED AT 846 PM CDT FRI APR 28 2017  
 
UPPER WAVE THAT PRODUCED THE SHOWERS AND THUNDERSTORMS THIS  
AFTERNOON, WITH MOST OF THE STORMS ALONG AND SOUTH OF A PARIS  
TO SHELBYVILLE LINE, HAS SHIFTED OFF TO OUR EAST EARLY THIS  
EVENING WITH MOST OF THE STRONGER CONVECTION THAT OCCURRED  
OVER SOUTHEAST ILLINOIS JUST SOUTH AND EAST OF OUR AREA.  
THE SYNOPTIC COOL FRONT WAS GIVEN A BIT OF A NUDGE TO THE  
SOUTH OF OUR AREA THANKS TO THE STRONG CONVECTION THAT PUSHED  
ACROSS THE I-70 CORRIDOR. CONVECTION CONTINUES TO FIRE JUST SOUTH  
OF THE BOUNDARY THIS EVENING AND EXPECT THAT AREA TO START TO  
SHIFT SLOWLY BACK NORTH TONIGHT ALONG WITH THE WARM FRONT. THIS  
WILL PRODUCE ANOTHER ROUND OF LOCALLY HEAVY RAINFALL OVER  
SOUTHEAST ILLINOIS ALONG WITH THE POSSIBILITY FOR SOME LARGE HAIL  
WITH SOME OF THE STRONGER CORES THAT DEVELOP NORTH. FURTHER NORTH,  
LOW CLOUDS, SOME PATCHY FOG AND DRIZZLE WILL DEVELOP OVERNIGHT  
WITH THE SHOWER THREAT SLOWLY ADVANCING UP INTO CENTRAL ILLINOIS  
AS THE WARM FRONT GRADUALLY EDGES NORTH AS WELL.  
 
WITH THE FRONTAL BOUNDARY EXPECTED TO SHIFT EVER SO SLOWLY NORTH  
ON SATURDAY, LOOK FOR PERIODS OF SHOWERS AND STORMS WITH HEAVY  
RAINFALL LIKELY, ESPECIALLY IN AREAS THAT SEE THE THUNDERSTORMS  
TRACK OVER THE SAME AREAS DURING THE DAY. HAVE MADE SOME MINOR  
ADJUSTMENTS TO THE OVERNIGHT PORTION OF THE FORECAST BUT OVERALL,  
THE CHANGES WERE NOT SIGNIFICANT ENOUGH TO WARRANT AN UPDATE AT  
THIS TIME.  
 

 
   
SHORT TERM
 
(THIS EVENING THROUGH SATURDAY)  
ISSUED AT 309 PM CDT FRI APR 28 2017  
 
HAVE EXPANDED THE FLASH FLOOD WATCH NORTHWEST TO THE IL RIVER FOR  
THIS WEEKEND, FROM TONIGHT THROUGH SUNDAY NIGHT. WIDESPREAD 3-5 INCH  
RAIN EXPECTED OVER CWA THIS WEEKEND, WITH LOCALLY UP TO 6 INCH  
AMOUNTS SE OF I-55 AND WEST OF I-57. 12Z FORECAST MODELS HAVE  
CONTINUED NW TREND OF HEAVIER RAIN AXIS OVER CENTRAL IL THIS  
WEEKEND. IN ADDITION TO HEAVY RAIN THREAT, SPC DAY1 OUTLOOK  
CONTINUES A SLIGHT RISK OF SEVERE THUNDERSTORMS LATE THIS AFTERNOON  
INTO MID EVENING SOUTH OF A PARIS TO SHELBYVILLE LINE WITH ENHANCED  
RISK SOUTH OF A ROBINSON TO FLORA LINE WHERE 2 INCH OR LARGER HAIL  
POSSIBLE. SPC DAY2 OUTLOOK HAS SLIGHT RISK FROM I-72 SOUTH ON SAT  
AFTERNOON/EVENING AS FRONTAL BOUNDARY LIFTS FURTHER NORTH. THE WARM  
FRONT IS CURRENTLY OVER THE SOUTHERN TIP OF IL, NORTH OF PADUCAH, KY  
AND OVER NORTHERN KY AND SOUTHERN MO. MODELS LIFT WARM FRONT  
NORTHWARD TOWARD I-70 EARLY THIS EVENING AND THEN APPEARS TO SLIP  
BACK SOUTH FOR A TIME OVERNIGHT BEFORE LIFTING BACK NORTH TOWARD I-  
72 ON SAT AFTERNOON. 1ST WAVE OF SHOWERS AND DEVELOPING  
THUNDERSTORMS WAS SE OF THE IL RIVER AND LIFTING NE. THIS WILL  
DIMINISH OVER CENTRAL IL BY EARLY EVENING, BUT CONTINUE OVER  
SOUTHEAST IL CLOSER TO THE FRONT. 2ND AREA OF CONVECTION TO SPREAD  
NE INTO CENTRAL IL LATER TONIGHT INTO SATURDAY.  
TEMPERATURES WILL BE TRICKY DEPENDING ON PLACEMENT OF FRONTAL  
BOUNDARY ESPECIALLY ON SATURDAY. WARMER 70S AND LOWER 80S WILL OCCUR  
SOUTH OF THE FRONT IN SOUTHEAST IL ON SAT WHILE MUCH COOLER  
UPPER 40S AND LOWER 50S IN NW IL, ALONG AND NW OF THE IL RIVER.  
   
LONG TERM
 
(SATURDAY NIGHT THROUGH FRIDAY)  
ISSUED AT 309 PM CDT FRI APR 28 2017  
 
THE HEAVIEST RAINS STILL APPEARS TO BE LATER SATURDAY AFTERNOON AND  
SATURDAY NIGHT AS PW VALUES ARE 1.5-2 INCHES WITH 50-60 SOUTHERLY  
850 MB WINDS ADVECTING IN DEEP MOISTURE. MODELS CONTINUE TO SHOW  
HEAVIEST RAIN AXIS BETWEEN THE IL RIVER AND I-57 DURING THAT TIME  
AND WHERE THE 4-5 INCH BAND AND LOCALLY 6 INCHES EXPECTED. FRONTAL  
BOUNDARY OVER CENTRAL IL SAT NIGHT SHOULD LIFT NORTH OF CWA DURING  
SUNDAY BEFORE COLD FRONT SWINGS EAST ACROSS CENTRAL/SOUTHEAST IL  
SUNDAY EVENING. THIS WILL KEEP HIGH CHANCES OF SHOWERS AND  
THUNDERSTORMS AROUND ESPECIALLY SUNDAY AFTERNOON/EVENING. SPC DAY3  
OUTLOOK HAS MARGINAL RISK OF SEVERE STORMS ACROSS AREA DURING THAT  
TIME AND WOULD NOT BE SURPRISED IF SLIGHT RISK SOUTH OF I-64 IN  
SOUTHERN IL WORKS ITS WAY FURTHER NORTHWARD WITH FUTURE UPDATES.  
SUNDAY SHOULD BE THE WARMEST DAY OF THE NEXT 7, WITH AREA GETTING  
INTO THE WARM SECTOR. HIGHS RANGE FROM 65-70F FROM PEORIA NORTH TO  
THE UPPER 70S/LOWER 80S OVER EAST CENTRAL AND SOUTHEAST IL.  
 
STRONG CUTOFF UPPER LEVEL LOW EJECTING NE OVER IA/WI ON MONDAY TO  
KEEP A FAIR AMOUNT OF LOW CLOUDS AROUND OVER IL ALONG WITH CHANCES  
OF SHOWERS ESPECIALLY NORTH OF I-70. MUCH COOLER HIGHS IN THE 50S  
WITH BREEZY WSW WINDS GUSTING 25-35 MPH. STRONG UPPER LEVEL LOW/TROF  
PULLS AWAY FROM CENTRAL IL ON TUE AFTERNOON WITH DRY WX RETURNING  
AND PARTLY TO MOSTLY SUNNY SKIES. HIGHS TUE IN THE LOW TO MID 60S,  
MILDEST OVER SW CWA.  
 
CHANCE OF SHOWERS SPREADS INTO SOUTHERN HALF OF CWA OVERNIGHT TUE  
NIGHT AND WED AND CONTINUES INTO WED NIGHT AND THU AS LOW PRESSURE  
PASSES SOUTH OF IL WHERE BETTER CHANCES OF THUNDERSTORMS WILL BE.  
BELOW NORMAL HIGHS MOSTLY IN THE LOWER 60S DURING MIDDLE OF NEXT  
WEEK WITH LOWS MOSTLY IN THE 40S.  
 

 
   
AVIATION
 
(FOR THE 00Z TAFS THROUGH 00Z SATURDAY EVENING)  
ISSUED AT 604 PM CDT FRI APR 28 2017  
 
VFR CIGS ARE EXPECTED TO GRADUALLY DETERIORATE TO MVFR AND IFR  
LATER TONIGHT AS MOISTURE STREAMS NORTH OF A WARM FRONT OVER  
SOUTHERN ILLINOIS. THE MOST CONCENTRATED AREA OF SHOWERS AND  
THUNDERSTORMS WILL BE ALONG AND SOUTH OF I-70 THIS EVENING  
WITH A GRADUAL SHIFT NORTH OF THE PRECIPITATION AS WE HEAD  
INTO THE EARLY MORNING HOURS, ROUGHLY IN THE 07Z-11Z TIME  
FRAME. AS THE WARM FRONT SHIFTS NORTH ON SATURDAY, A LARGE  
AREA OF SHOWERS AND STORMS WILL AFFECT THE TAF SITES  
ACCOMPANIED BY MVFR AND LOCAL IFR CIGS AND VSBYS, ESPECIALLY  
IN AND NEAR ANY THUNDERSTORM. SURFACE WINDS TONIGHT WILL BE  
BACKING MORE INTO AN EAST TO NORTHEAST DIRECTION AND SHOULD  
HOLD FROM AN EASTERLY DIRECTION ON SATURDAY. SPEEDS WILL BE  
RATHER LIGHT TONIGHT, GENERALLY FROM 7 TO 12 KTS, AND THEN  
PICK UP IN SPEED TO BETWEEN 12 TO 17 KTS SATURDAY MORNING.  
 

 
   
ILX WATCHES/WARNINGS/ADVISORIES
 
 
FLASH FLOOD WATCH THROUGH MONDAY MORNING FOR ILZ031-037-038-  
041>057-061>063-066>068-071>073.  
 

 
 

 
 
UPDATE...SMITH  
SHORT TERM...07  
LONG TERM...07  
AVIATION...SMITH  
 
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