074  
FXUS63 KLSX 161734  
AFDLSX  
 
AREA FORECAST DISCUSSION...UPDATED AVIATION  
NATIONAL WEATHER SERVICE SAINT LOUIS MO  
1134 AM CST MON DEC 16 2024  
   
KEY MESSAGES
 
 
- SHOWERS AND A FEW THUNDERSTORMS WILL BE FOUND MAINLY ACROSS  
SOUTHEAST MISSOURI AND SOUTHWEST ILLINOIS THIS MORNING.  
 
- THERE IS ANOTHER CHANCE OF RAIN ON TUESDAY NIGHT AND WEDNESDAY  
WITH THE BEST CHANCE (60-70%) ACROSS SOUTHEAST MISSOURI AND  
SOUTHWEST ILLINOIS.  
 
- DRY AND COOLER WEATHER IS EXPECTED LATE THIS WEEK INTO THE WEEKEND.  
 

 
   
SHORT TERM
 
(THROUGH LATE TUESDAY AFTERNOON)  
ISSUED AT 322 AM CST MON DEC 16 2024  
 
LATEST RADAR TRENDS CONTINUE TO SHOW SHOWERS EXPANDING ACROSS  
SOUTHERN MISSOURI AND SOUTHERN ILLINOIS IN A STRONG BAND OF LOW  
LEVEL MOISTURE CONVERGENCE AHEAD OF THE MID-LEVEL TROUGH OVER THE  
PLAINS. ISOLATED THUNDERSTORMS ARE EMBEDDED WITHIN THESE BANDS OF  
SHOWERS AS THE LATEST SPC MESOANALYSIS IS SHOWING MUCAPES OF 500-  
1000+ J/KG WITH DEEP LAYER SHEAR OF 20 TO 30 KNOTS. RECENT RUNS OF  
THE CAMS CONTINUE TO SHOW THAT RAIN WILL EXPAND ACROSS AREAS SOUTH  
OF I-44 IN MO AND SOUTH OF I-70 IN IL BEFORE THE FORCING ASSOCIATED  
WITH THE LOW LEVEL JET WILL MOVE SOUTHEAST OF THE CWA LATER THIS  
MORNING. UNTIL THEN, THERE COULD BE SOME STRONGER STORMS THAT COULD  
PRODUCE SOME SMALL HAIL AND HEAVIER DOWNPOURS. WHILE MOST OF THE  
AREA WILL NOT SEE AS MUCH RAINFALL AS SATURDAY'S SYSTEM, THE HREF  
LPMM IS SHOWING UP TO 1" OF RAINFALL OVER THE FAR SOUTHERN PART OF  
THE CWA. THE HREF HAS THE UPPER TROUGH MOVING EAST OF THE CWA BY  
LATE THIS AFTERNOON WITH A SHORTWAVE RIDGE MOVING ACROSS THE AREA ON  
TUESDAY. THIS WILL KEEP THE AREA DRY THIS AFTERNOON THROUGH  
TOMORROW.  
 
THE COLD FRONT THAT IS CURRENTLY ENTERING THE WESTERN PART OF  
MISSOURI WILL MOVE THROUGH THE CWA LATER TODAY. THERE WILL BE A  
LARGE SPREAD IN HIGHS TODAY WITH 60S OVER THE SOUTHEAST HALF OF THE  
CWA COMPARED TO AROUND 50 DEGREES OVER NORTHEAST MISSOURI. A  
SURFACE HIGH WILL MOVE ACROSS MISSOURI AND ILLINOIS TONIGHT CAUSING  
LIGHT WINDS AND CLEAR SKIES ALLOWING TEMPERATURES TO FALL BACK INTO  
THE LOWER 30S. WINDS WILL TURN OUT OF THE SOUTHEAST AHEAD OF THE  
NEXT SYSTEM ON TUESDAY UNDER A PARTLY SUNNY SKY CAUSING HIGHS TO  
CLIMB BACK INTO THE LOWER TO MID 50S.  
 
BRITT  
 

 
   
LONG TERM
 
(TUESDAY NIGHT THROUGH SUNDAY)  
ISSUED AT 322 AM CST MON DEC 16 2024  
 
MODEL GUIDANCE HAS BEEN CONSISTENT WITH THE NEXT TROUGH MOVING  
ACROSS THE MIDWEST TUESDAY NIGHT INTO WEDNESDAY. THE LREF  
CONTINUES TO SHOW THAT ITS HIGHEST NUMBER OF ENSEMBLE MEMBERS  
SHOWING PRECIPITATION ON TUESDAY NIGHT WILL ONCE AGAIN BE OVER  
THE SOUTHEAST HALF OF THE CWA. TEMPERATURES WILL FALL TOWARD  
FREEZING LATE ON TUESDAY NIGHT OVER THE NORTHERN CWA WHICH COULD  
LEAD TO SOME SNOW MIXING IN WITH THE RAIN BEFORE IT ENDS, BUT LESS  
THAN 10 PERCENT OF THE LREF MEMBERS ARE SHOWING A CHANCE OF SNOW  
AT UIN WHICH LOWERS CONFIDENCE IN THIS POTENTIAL.  
 
A TROUGH WILL MOVE FROM THE NORTHERN HIGH PLAINS ON WEDNESDAY NIGHT  
INTO THE GREAT LAKES ON THURSDAY NIGHT. THE LATEST TRACK KEEPS  
CHANCES OUT OF THE CWA ON THURSDAY NIGHT WITH THE NUMBER OF LREF  
MEMBERS PRODUCING PRECIPITATION AT UIN OR SPI AT LESS THAN 10  
PERCENT. THE DRY WEATHER LOOKS LIKE IT WILL CONTINUE INTO THE  
WEEKEND AS AN UPPER RIDGE WILL BE BUILDING INTO THE AREA.  
 
TWO COLD FRONTS WILL MOVE THROUGH THE AREA THIS WEEK, ONE ASSOCIATED  
WITH THE FIRST UPPER TROUGH ON TUESDAY NIGHT AND WEDNESDAY AND THE  
SECOND WITH THE CLIPPER ON THURSDAY NIGHT. BOTH FRONTS WILL BRING  
COOLER AIR WITH HIGH TEMPERATURES BEHIND THE FIRST FRONT ON  
WEDNESDAY AND THURSDAY IN THE 40S AND HIGHS BEHIND THE SECOND FRONT  
FRIDAY INTO THE WEEKEND IN THE 30S.  
 
BRITT  
 

 
   
AVIATION
 
(FOR THE 18Z TAFS THROUGH 18Z TUESDAY AFTERNOON)  
ISSUED AT 1128 AM CST MON DEC 16 2024  
 
A COLD FRONT IS CURRENTLY MOVING ACROSS THE REGION, AND IS IN THE  
VICINITY OF KSUS, KSTL, AND KCPS AS OF THE START OF THE PERIOD.  
CURRENT LOW CLOUDS IN THE ST. LOUIS METRO AREA WILL BE PUSHED  
EASTWARD BY THE FRONT, WITH VFR FLIGHT CONDITIONS EXPECTED VERY  
SOON AT KCPS. WITH THE PASSAGE OF THE FRONT, WINDS WILL PICK UP  
OUT OF THE WEST-NORTHWEST THROUGH THE REMAINDER OF THE AFTERNOON,  
DYING DOWN WITH THE SETTING SUN. HIGH PRESSURE MOVING OVERHEAD  
TONIGHT WILL CAUSE WINDS TO GO LIGHT TO VARIABLE BEFORE THEY  
INCREASE IN SPEED TOMORROW MORNING OUT OF THE SOUTH-SOUTHEAST.  
 
ELMORE  
 

 
   
LSX WATCHES/WARNINGS/ADVISORIES
 
 
MO...NONE.  
IL...NONE.  

 
 

 
 
WFO LSX  
 
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