407  
FXUS63 KILX 201935  
AFDILX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE LINCOLN IL  
235 PM CDT SUN APR 20 2014  
   
DISCUSSION
 
 
ISSUED 235 PM CDT SUN APR 20 2014  
 
ANOTHER PLEASANTLY MILD DAY CONTINUES TO UNFOLD ACROSS CENTRAL AND  
SOUTHEAST ILLINOIS. AS EXPECTED, TEMPERATURES ARE A LITTLE WARMER  
THAN YESTERDAY THANKS TO INCREASING SOUTHERLY FLOW IN ADVANCE OF A  
DEVELOPING STORM SYSTEM IN THE PLAINS. MAIN FORECAST CONCERNS TODAY  
REVOLVE AROUND SHOWER/STORM CHANCES TOMORROW WITH THE PASSAGE OF  
THE PLAINS SYSTEM, AS WELL AS WITH A STRONGER SYSTEM FOR THURSDAY.  
 
SHORT TERM...TONIGHT THROUGH WEDNESDAY:  
 
THE APPROACHING PLAINS SYSTEM IS STILL EXPECTED TO PRODUCE SHOWERS  
AND A FEW THUNDERSTORMS AS IT PASSES THROUGH MONDAY INTO MONDAY  
NIGHT. HOWEVER, IT WILL NOT BE A SIGNIFICANT SYSTEM IN TERMS OF  
PRECIPITATION AMOUNTS OR STORM INTENSITY.  
 
THE FORCING WITH THIS SYSTEM WILL COME COURTESY OF LOOSELY PHASED  
NORTHERN/SOUTHERN STREAM WAVES, BUT THE MORE VIGOROUS FORCING WITH  
THESE FEATURES SHOULD STAY NORTH/SOUTH RESPECTIVELY OF THE  
FORECAST AREA. IN ADDITION, ONLY MODEST INSTABILITY (CAPE VALUES  
AOB 1000 J/KG), AND WEAK BULK SHEAR (LESS THAN 20 KTS) ARE  
ANTICIPATED.  
 
THE PRECIPITATION THREAT WILL COME TO AN END FAIRLY QUICKLY MONDAY  
NIGHT AS THE SYSTEM PUSHES EAST OF THE AREA. QUIET WEATHER AND MORE  
SEASONABLE TEMPERATURES (HIGHS IN THE 60S) WILL ACCOMPANY THE  
UPPER/SURFACE RIDGING THAT WILL BUILD IN BEHIND THE SYSTEM INTO  
MIDWEEK.  
 
LONG TERM...WEDNESDAY NIGHT THROUGH SUNDAY:  
 
THE NEXT, MORE VIGOROUS, SYSTEM IS STILL ON TRACK TO BRING  
SHOWERS/STORMS TO THE AREA FOR THURSDAY INTO THURSDAY NIGHT, MOSTLY  
ASSOCIATED WITH THE PASSAGE OF THE SYSTEM'S COLD FRONT. HOWEVER,  
CAN'T RULE OUT A STRAY SHOWER OR STORM IN THE PRE-SYSTEM WARM  
ADVECTION REGIME AS EARLY AS WEDNESDAY OR WEDNESDAY NIGHT. HOWEVER,  
MOST OF THIS PRECIPITATION SHOULD OCCUR NORTH OF THE FORECAST AREA.  
 
AFTER A BRIEF SURGE OF WARMER AIR AHEAD OF THURSDAY'S SYSTEM,  
TEMPERATURES WILL COOL BACK TO NORMAL LEVELS, POSSIBLY COLDER, FOR  
THE WEEKEND. MODEL AGREEMENT AND RUN-TO-RUN CONSISTENCY WITH THE  
OVERALL WEATHER PATTERN FOR THE WEEKEND IS NOT VERY GOOD. WHILE  
THEY GENERALLY AGREE ON A COOLER TREND, THEY DON'T AGREE WITH HOW  
QUICKLY WE GET THERE. THE TIMING DIFFERENCES ARE ALSO REFLECTED IN  
HOW QUICKLY PRECIPITATION CHANCES RETURN. THE ECMWF HAS BEEN MOST  
AGGRESSIVE BY FAR WITH THE ARRIVAL OF THE COOLER AIR AND WETTER  
CONDITIONS, ALTHOUGH THE LATEST GFS HAS TRENDED CLOSER TO THE  
ECMWF. PLAN TO KEEP POPS ON THE LOWER SIDE, AND TEMPERATURES A BIT  
MORE MODERATE, UNTIL A BETTER MODEL CONSENSUS IS REACHED.  
 
BAK  

 
   
AVIATION
 
 
ISSUED 1221 PM CDT SUN APR 20 2014  
 
VFR CONDITIONS ON TAP THROUGH THE PERIOD. A BIT OF GUSTINESS  
EXPECTED ALONG THE ILLINOIS RIVER THIS AFTERNOON AFFECTING KPIA,  
DUE TO TIGHTENING PRESSURE GRADIENT TO THE WEST, BUT THIS SHOULD  
SUBSIDE THIS EVENING. MAINLY HIGH CLOUDS ON TAP THROUGH SUNRISE.  
AFTER THAT, A LOWERING OF CEILINGS IS EXPECTED AS A STORM SYSTEM  
APPROACHES FROM THE WEST. SOME OF THE MODELS ARE SUGGESTING SOME  
SCATTERED SHOWERS BY LATE MORNING, BUT WILL KEEP THE TAFS DRY FOR  
NOW AS THE FORECAST SOUNDINGS ARE STILL RATHER DRY BELOW 5000 FT.  
 
GEELHART  

 
   
ILX WATCHES/WARNINGS/ADVISORIES
 
 
NONE.  

 
 

 
 
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