700  
FXUS63 KILX 292336  
AFDILX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE LINCOLN IL  
636 PM CDT MON MAY 29 2017  
   
SHORT TERM
 
(THIS EVENING THROUGH TUESDAY)  
ISSUED AT 305 PM CDT MON MAY 29 2017  
 
A SLOW-MOVING COLD FRONT AND VORTICITY MAX WILL PUSH ACROSS THE  
SOUTHEAST PORTION OF OUR FORECAST AREA THE REST OF THE AFTERNOON  
INTO THIS EVENING. WHILE NO SHOWERS HAVE DEVELOPED TO THIS POINT,  
THE HIGH RES MODELS ARE ALL POINTING TOWARD ISOLATED  
SHOWERS/STORMS DEVELOPING ALONG THE BOUNDARY LATE THIS AFTERNOON  
INTO EARLY EVENING. MUCAPES OF 1000 J/KG SHOULD BE SUFFICIENT FOR  
THAT TO OCCUR. HAVE LINGERED LOW CHANCE/SLIGHT CHANCE POPS ALONG  
AND SOUTH OF I-70 EARLY THIS EVENING. SUBSIDENCE IN THE POST-  
FRONTAL AIRMASS SHOULD SET UP MOSTLY CLEAR AND SEASONABLE  
CONDITIONS FOR THE REMAINDER OF THE NIGHT. LOW TEMPS SHOULD  
SETTLE OUT IN THE LOW TO MID 50S.  
 
TUESDAY SHOULD START OUT SUNNY, BUT AFTERNOON CONDITIONS WILL TURN  
MORE CLOUDY WITH SPOTTY SHOWERS/STORMS DEVELOPING AHEAD OF THE  
NEXT TROUGH/COLD FRONT. ONCE AGAIN, THE FRONT WILL BE MOISTURE  
STARVED. THERE WILL BE LIMITED INSTABILITY IN THE 500-800 J/KG  
RANGE, BUT BULK SHEAR OF 50-60KTS WILL BE A CATALYST TOWARD STORM  
DEVELOPMENT ALONG THE FRONT. HAVE INCLUDED SLIGHT CHANCE POPS  
TUESDAY AFTERNOON ALONG AND WEST OF I-55. ENOUGH MORNING INTO  
EARLY AFTERNOON SUNSHINE SHOULD PUSH HIGH TEMPS INTO THE LOW 70S  
NORTH OF I-74, WITH UPPER 70S SOUTH OF I-70.  
   
LONG TERM
 
(TUESDAY NIGHT THROUGH MONDAY)  
ISSUED AT 305 PM CDT MON MAY 29 2017  
 
THE EXTENDED FORECAST WILL BE PRIMARILY INFLUENCED BY A LONG WAVE  
TROUGH ACROSS EASTERN CANADA AND THE EASTERN HALF OF THE LOWER 48.  
AN UPPER LOW CENTERED OVER NW ONTARIO WILL PINWHEEL NORTH AND THEN  
SOUTH AGAIN OVER THE NEXT SEVERAL DAYS, SETTING THE STAGE FOR  
PERIODS OF SHOWERS AND STORMS. TUESDAY NIGHT WILL SEE A COLD FRONT  
DEPART THROUGH THE SOUTHEAST HALF OF OUR FORECAST AREA, TRIGGERING  
SHOWERS/STORMS FOR AREAS SE OF THE ILLINOIS RIVER.  
 
WEDNESDAY AND WED NIGHT LOOK TO BE A DRY PERIOD, AS HIGH PRESSURE  
PASSES ACROSS ILLINOIS, BRINGING OUR COOLEST TEMPERATURES OF THE  
NEXT WEEK. HIGHS WED WILL BE A COUPLE DEGREES COOLER THAN TUES,  
BUT STILL MAINLY IN THE 70S. WED NIGHT LOWS WILL MIRROR TUESDAY  
NIGHT, WITH LOW 50S NORTH AND UPPER 50S SOUTH.  
 
ONCE THE HIGH SHIFTS OFF TO THE EAST, A WARM FRONT WILL LIFT  
NORTHWARD INTO THE AREA ON THURSDAY. THE EXTENDED MODELS CONTINUE  
TO POINT TOWARD AN MCS DEVELOPING ACROSS THE PLAINS WEDNESDAY  
NIGHT, THEN TRACKING E/SE TOWARD CENTRAL ILLINOIS BY THURSDAY  
MORNING. THE ECMWF, GFS, AND NAM ALL GENERALLY SHOW THE WAVE  
ARRIVING THURSDAY MORNING, THEN WEAKENING AS IT PUSHES ACROSS  
ILLINOIS DURING THE DAY. DESPITE MARGINAL SYNOPTIC FORCING, THE  
PRESENCE OF A WARM FRONT ACROSS ILLINOIS WARRANTS AT LEAST CHANCE  
POPS THURSDAY INTO THURSDAY EVENING. THERE ARE INDICATIONS OF A  
BREAK IN THE RAIN FROM MIDNIGHT THURSDAY TO NOON ON FRIDAY.  
 
THE WARM FRONT WILL CONTINUE A SLOW PROGRESSION NORTHWARD FRIDAY  
NIGHT INTO SATURDAY, PUTTING OUR AREA FIRMLY IN THE WARM SECTOR.  
ISOLATED TO SCATTERED SHOWERS/STORMS ARE IN THE FORECAST FOR  
SATURDAY INTO EARLY SUNDAY DUE TO LOW PRESSURE MOVING EAST ALONG  
THE FRONT AND PASSING ACROSS NORTHERN ILLINOIS SUNDAY MORNING. A  
BREAK IN THE RAIN LOOKS TO CLOSE OUT THE EXTENDED FORECAST SUNDAY  
AFTERNOON THROUGH MONDAY AS HIGH PRESSURE ARRIVES BEHIND THE  
DEPARTING LOW.  
 

 
   
AVIATION
 
(FOR THE 00Z TAFS THROUGH 00Z TUESDAY EVENING)  
ISSUED AT 635 PM CDT MON MAY 29 2017  
 
A SLOW MOVING COLD FRONT WILL TRIGGER A FEW SHOWERS AND ISOLATED  
THUNDERSTORMS THIS EVENING FROM NEAR KDEC-KCMI SOUTHEASTWARD THEN  
VFR CONDITIONS EXPECTED UNTIL TUESDAY AFTERNOON. AT THAT POINT,  
ANOTHER COLD FRONTAL BOUNDARY WILL SWEEP ACROSS THE AREA BRINGING  
ANOTHER CHANCE FOR WIDELY SCATTERED SHOWERS AND ISOLATED  
THUNDERSTORMS. WINDS W, DECREASING TO UNDER 10 KTS THIS EVENING,  
THEN INCREASING AFTER 15Z MONDAY, BECOMING 12-16KTS WITH GUSTS UP  
TO 25 KTS.  
 

 
   
ILX WATCHES/WARNINGS/ADVISORIES
 
 
NONE.  
 

 
 

 
 
SHORT TERM...SHIMON  
LONG TERM...SHIMON  
AVIATION...37  
 
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