353  
FXUS63 KILX 300138  
AFDILX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE LINCOLN IL  
838 PM CDT FRI MAY 29 2015  
   
UPDATE
 
 
ISSUED AT 830 PM CDT FRI MAY 29 2015  
 
SHOWERS CONTINUE TO SLOWLY DISSIPATE OVER EAST AND SOUTHEAST IL  
WHILE A BAND OF SHOWERS AND ISOLATED THUNDERSTORMS TRACKS  
NORTHEAST OUT OF CENTRAL MISSOURI THIS EVENING AHEAD OF AN UPPER  
LEVEL SHORTWAVE OVER SOUTHERN MO. THIS WILL BRING ANOTHER ROUND  
OF SHOWERS AND THUNDERSTORMS TO THE FORECAST AREA OVERNIGHT...  
STARTING OUT WEST AND GRADUALLY EDGING TO THE EAST DURING THE  
EARLY MORNING HOURS. WE SHOULD SEE COVERAGE INCREASE LATE  
TONIGHT AS MOST MODELS INDICATE SOME IMPRESSIVE 850 MB THETA-E  
ADVECTION ACCOMPANIED BY A 35-45 KT LOW LEVEL JET FEEDING IN  
UNSEASONABLY HIGH PRECIPITABLE WATER VALUES INTO THE REGION.  
GREATEST 850 MB SPEED CONVERGENCE OVER WESTERN IL THRU 06Z  
AND THEN SPREADS EAST OVERNIGHT WITH THE HIGHER THREAT FOR  
SOME HEAVY RAINFALL OVER WEST CENTRAL THRU OUR NORTHERN  
COUNTIES. WONDER WHAT AFFECT...IF ANY...THE LARGER COMPLEX  
OF SEVERE STORMS OVER OKLAHOMA INTO ARKANSAS WILL HAVE ON  
OUR MOISTURE FEED NORTHWARD TONIGHT.  
 
HAVE MADE SOME ADJUSTMENTS TO THE HOURLY TEMP GRIDS THANKS TO  
THE SCATTERED RAINFALL AND OUTFLOW BOUNDARIES...AS WELL AS SOME  
TWEAKING TO THE POPS FOR THE OVERNIGHT HOURS ACROSS THE EAST.  
SHOULD HAVE THE UPDATE OUT BY 900 PM.  
 

 
   
SHORT TERM
 
(TONIGHT)  
ISSUED AT 257 PM CDT FRI MAY 29 2015  
 
DESPITE A MODERATELY UNSTABLE AIRMASS CHARACTERIZED BY SBCAPES OF  
AROUND 2000J/KG...19Z/2PM RADAR IMAGERY SHOWS VERY LITTLE CONVECTION  
ACROSS CENTRAL ILLINOIS. VERY WEAK WIND SHEAR AND AN OVERALL LACK  
OF SIGNIFICANT FORCING APPEARS TO BE KEEPING THE STORMS AT BAY THIS  
AFTERNOON. CLUSTERS OF CONVECTION ARE DEVELOPING FURTHER SOUTH FROM  
JUST EAST OF SAINT LOUIS INTO THE OZARKS. THIS ACTIVITY WILL SLOWLY  
LIFT NORTHEASTWARD AND IMPACT PORTIONS OF THE KILX CWA LATE THIS  
AFTERNOON...MAINLY ALONG AND SOUTH OF A DANVILLE TO SHELBYVILLE  
LINE. OVERALL AREAL COVERAGE WILL REMAIN RELATIVELY LOW...SO WILL  
ONLY GO WITH CHANCE POPS THROUGH EARLY EVENING. RAIN CHANCES WILL  
BEGIN TO INCREASE TONIGHT AS STRONGER FORCING ASSOCIATED WITH A  
SHORT-WAVE TROUGH OVER OKLAHOMA/EAST TEXAS APPROACHES FROM THE  
SOUTHWEST. MODELS ARE ALL OVER THE PLACE...HOWEVER CONSENSUS OF  
HIGH-RES SOLUTIONS FOCUSES HIGHEST POPS ACROSS THE WESTERN HALF OF  
THE CWA FROM MID-EVENING THROUGH THE OVERNIGHT HOURS. BAND OF  
PRECIP WILL GRADUALLY SPREAD INTO EAST-CENTRAL ILLINOIS TOWARD DAWN  
SATURDAY...AS A COLD FRONT APPROACHES FROM THE WEST.  
   
LONG TERM
 
(SATURDAY THROUGH FRIDAY)  
ISSUED AT 257 PM CDT FRI MAY 29 2015  
 
MODELS GENERALLY SHOW A COLD FRONT REACHING AROUND I-55 BY MID  
MORNING SATURDAY...REACHING SOUTHEASTERN ILLINOIS BY SATURDAY  
EVENING AND EXITING THE CENTRAL IL FORECAST AREA. AHEAD OF THE  
FRONT...MODEST SFC-6KM BULK SHEAR OF GENERALLY 20 KTS WILL  
PREVAIL...INCREASING TO AROUND 30 KTS NEAR THE FRONT. INSTABILITY  
GENERALLY AROUND 1500-2500 J/KG ARE INDICATED AHEAD OF THE  
FRONT...DEPENDING ON SURFACE HEATING. THESE INGREDIENTS WILL COME  
TOGETHER...ALONG WITH AN UPPER LEVEL SHORTWAVE...DURING THE DAY  
SATURDAY FOR SCATTERED SHOWERS AND THUNDERSTORMS ESPECIALLY FROM  
AROUND THE ILLINOIS RIVER SOUTHEASTWARD. THUNDERSTORM ACTIVITY WILL  
SHIFT FARTHER SOUTHEASTWARD THROUGH THE DAY AND EVENING AS THE FRONT  
SLIPS SOUTHEASTWARD. A MARGINAL THREAT FOR SEVERE THUNDERSTORMS IS  
FORECAST BY SPC WITH THE MAIN THREAT BEING SEVERE WIND GUSTS. WITH  
THE FRONTAL BOUNDARY LINGERING NEAR THE SOUTHERN TIP OF ILLINOIS  
SUNDAY MORNING...AT LEAST A SLIGHT CHANCE OF THUNDERSTORMS WILL  
REMAIN THROUGH SUNDAY SOUTH OF I-70 AS ANOTHER UPPER LEVEL WAVE  
PASSES THROUGH THE AREA. TEMPERATURES WILL DROP OFF SUBSTANTIALLY  
FOR SATURDAY AND SUNDAY. HIGHS AROUND 67 NEAR GALESBURG TO AROUND 80  
JUST SOUTH OF I-70 SATURDAY...THEN MID TO UPPER 60S ACROSS THE AREA  
SUNDAY. SOME LOWS NORTH OF I-72 SHOULD REACH INTO THE 40S SATURDAY  
AND SUNDAY NIGHT.  
 
A BUILDING HIGH PRESSURE RIDGE SHOULD BRING SUBSIDENCE AND DRY  
CONDITIONS THROUGH THE EARLY PART OF NEXT WORK WEEK. BY MID TO LATE  
WEEK...A CUT-OFF UPPER LOW OVER THE GULF COAST COULD HELP TRANSPORT  
A RETURN OF MOIST/UNSTABLE CONDITIONS TO THE MIDWEST...WITH  
PRECIPITABLE WATER VALUES AROUND 1.5-1.75 INCHES POSSIBLE. MODELS  
CONTINUE TO DISAGREE ON THE POSITION OF THE RIDGE/CUT-OFF...AND THIS  
WILL IMPACT THE MOISTURE RETURN. ALTHOUGH A STRONG LIFTING MECHANISM  
ISNT EXPECTED AT THIS TIME...DAILY CHANCES FOR THUNDERSTORMS WILL BE  
POSSIBLE MAINLY DRIVEN BY DAYTIME HEATING AND CONVECTIVE  
OUTFLOWS...PERHAPS AN MCS OVER THE UPPER MIDWEST. EXPECT A GRADUAL  
WARMING TREND THROUGH THE WEEK WITH HIGHS IN THE LOW 70S MONDAY  
REACHING THE MID 80S FOR THURSDAY AND FRIDAY.  
 

 
   
AVIATION
 
(FOR THE 00Z TAFS THROUGH 00Z SATURDAY EVENING)  
ISSUED AT 550 PM CDT FRI MAY 29 2015  
 
WIDELY SCATTERED CONVECTION THIS EVENING WITH DEC AND BMI THE  
MOST LIKELY TO BE AFFECTED BY POSSIBLE BRIEF MVFR CIGS.  
OTHERWISE...VFR CIGS ARE EXPECTED THRU ABOUT MIDNIGHT BEFORE THE  
NEXT WAVE OF SHOWERS AND THUNDERSTORMS MOVES IN FROM THE SOUTHWEST  
AFTR 05Z MAINLY AFFECTING OUR WESTERN TAF SITES INITIALLY WITH  
CIGS DROPPING TO MVFR OR POSSIBLY IFR FOR A BRIEF TIME IN ANY  
HEAVY TSRA. AFTER ABOUT 08Z...OUR EASTERN TAF SITES WILL GET IN ON  
SOME OF THE SHOWERS WITH CIGS DROPPING TO MVFR IN THE 09Z-12Z TIME  
FRAME.  
 
AS A FRONTAL BOUNDARY PUSHES ACROSS THE AREA LATE SATURDAY MORNING  
THRU THE AFTERNOON HOURS...WE ARE EXPECTING MVFR WITH OCCASIONAL  
IFR CIGS IN SHOWERS AND TSRA INTO THE AFTERNOON. LOOK FOR SOUTHWEST  
WINDS OF 7 TO 12 KTS TONIGHT TO CONTINUE OUT OF A SOUTHERLY  
DIRECTION EARLY SATURDAY MORNING BEFORE SWITCHING INTO THE NORTH  
AND NORTHEAST DIRECTION OVER OUR NORTHERN TAF SITES BY NOON OR  
SHORTLY THEREAFTER...AND INTO THE NORTHWEST AT 10 TO 20 KTS OVER  
THE REMAINDER OF THE FORECAST AREA BY 21Z.  
 

 
   
ILX WATCHES/WARNINGS/ADVISORIES
 
 
NONE.  

 
 

 
 
UPDATE...SMITH  
SHORT TERM...BARNES  
LONG TERM...ONTON  
AVIATION...SMITH  
 
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