713  
FXUS63 KLSX 061119  
AFDLSX  
 
AREA FORECAST DISCUSSION...UPDATED AVIATION  
NATIONAL WEATHER SERVICE SAINT LOUIS MO  
619 AM CDT MON OCT 6 2025  
   
KEY MESSAGES
 
 
- THERE IS A 20-60% CHANCE OF RAIN TODAY AND TONIGHT WITH THE  
BEST CHANCE ACROSS FAR NORTHEAST MISSOURI AND WEST-CENTRAL  
ILLINOIS BEHIND A COLD FRONT.  
 
- TEMPERATURES WILL BEGIN COOLING TO NEAR NORMAL TUESDAY, LASTING  
THROUGH AT LEAST THURSDAY.  
 

 
   
SHORT TERM
 
(THROUGH LATE TUESDAY AFTERNOON)  
ISSUED AT 330 AM CDT MON OCT 6 2025  
 
A COLD FRONT IS CURRENTLY DRAPED FROM CENTRAL IOWA INTO CENTRAL  
KANSAS, JUST CREEPING INTO NORTHEAST MISSOURI. THROUGH THE COURSE OF  
THE DAY THIS FRONT WILL EDGE EASTWARD TOWARDS THE CWA, DRIVEN ALOFT  
BY A LARGE MID-LEVEL TROUGH RIDING EAST ALONG THE US-CANADA BORDER.  
PRECIPITATION FROM THIS FRONT IS EXPECTED TO FORM ALONG AND BEHIND  
THE FRONT, AND SO IS NOT EXPECTED TO IMPACT THE AREA UNTIL TONIGHT.  
 
SHOWERS AND THUNDERSTORMS ARE STILL POSSIBLE AHEAD OF THE FRONT  
ACROSS MUCH OF THE FORECAST AREA, DRIVEN BY DIURNAL INSTABILITY IN  
AN UNCAPPED AND MARGINALLY UNSTABLE ENVIRONMENT. COVERAGE WILL BE  
ISOLATED TO LARGELY SCATTERED, AND ONLY A LUCKY FEW WILL SEE RAIN  
TODAY. WARM CLOUD DEPTHS GREATER THAN 10KFT AND ABOVE NORMAL  
PRECIPITABLE WATER VALUES WILL SUPPORT EFFICIENT RAINFALL, AND IN  
THE STRONGEST STORMS RAINFALL AMOUNTS WILL APPROACH 1 INCH.  
 
AT THE SAME TIME, A MID-LEVEL SHORTWAVE WILL FLOW NORTH INTO THE MID-  
MISSISSIPPI VALLEY ALONG THE WESTERN EDGE OF A DEPARTING MID-LEVEL  
RIDGE. THIS SHORTWAVE WILL PRODUCE SHOWERS AND THUNDERSTORMS,  
INCREASING IN COVERAGE AS INSTABILITY BUILDS DURING THE DAY. THE  
BULK OF THE PRECIPITATION HAS SHIFTED SOUTHEAST OUT OF THE FORECAST  
AREA COMPARED TO 24 HOUR AGO. THE EXACT LOCATION OF THE RAINFALL  
WILL DEPEND ON THE MOVEMENT OF THE SHORTWAVE, AND A SLIGHT SHIFT TO  
THE NORTHWEST WOULD BRING MORE RAIN INTO THE FORECAST AREA. THE  
STRONGEST STORMS IN THIS SYSTEM WILL BE ABLE TO PRODUCE UP TO 2-3"  
OF RAIN GIVEN THE DEEP WARM CLOUD DEPTHS AND THE NEARLY 2"  
PRECIPITABLE WATER VALUES (99TH PERCENTILE).  
 
THE RESULT OF ALL OF THIS IS AT LEAST A 20% CHANCE OF RAIN ACROSS  
THE AREA THROUGH MOST OF TODAY AND CLOUD COVER HEMMING THE REGION IN  
FROM THE NORTHWEST AND SOUTHEAST. THE CLOUD COVER AND RAIN CHANCES  
WILL KNOCK A FEW DEGREES OFF TODAY'S HIGHS AS COMPARED TO  
YESTERDAY'S TOASTY TEMPERATURES.  
 
THE COLD FRONT WILL CONTINUE TO PROGRESS INTO THE REGION THROUGH THE  
AFTERNOON AND EVENING, BRINGING A CHANCE OF RAIN TO NORTHEAST  
MISSOURI AND WEST-CENTRAL ILLINOIS OVERNIGHT. THIS WILL BE THE BEST  
CHANCE FOR RAIN ACROSS THE CWA, YET WON'T LAST LONG AS THE LOW-LEVEL  
FRONTOGENESIS AND SURFACE CONVERGENCE WEAKENS AS THE FRONT  
PROGRESSES THROUGH THE AREA. COVERAGE IS EXPECTED TO WEAKEN  
OVERNIGHT BEFORE REACHING THE I-70 CORRIDOR, AND PASS THROUGH THE  
REMAINDER OF THE CWA DRY ON TUESDAY. ISOLATED SHOWERS AND  
THUNDERSTORMS ARE POSSIBLE AHEAD OF THE FRONT ACROSS FAR SOUTHEAST  
MISSOURI AND SOUTHERN ILLINOIS WHERE ANOTHER DISTURBANCE WILL PUSH  
THROUGH THE BOOTHEEL/SOUTHERN ILLINOIS REGION. ONCE AGAIN WE WILL BE  
ON THE NORTHWEST PERIPHERY OF THIS RAIN UNLESS THE TRACK  
OF THE DISTURBANCE SHIFTS.  
 
TEMPERATURES ON TUESDAY WILL DEPEND ON THE LOCATION OF THE FRONT  
DURING THE MORNING AND EARLY AFTERNOON, WITH TEMPERATURES BEHIND THE  
FRONT NEAR NORMAL THANKS TO THE INCOMING COOLER CONTINENTAL AIR.  
AREAS AHEAD OF THE FRONT WILL WARM INTO THE MID TO UPPER 70S UNDER  
SOUTHERLY FLOW, THOUGH WARMING WILL BE STUNTED BY LINGERING CLOUD  
COVER.  
 
DELIA  
 

 
   
LONG TERM
 
(TUESDAY NIGHT THROUGH SUNDAY)  
ISSUED AT 330 AM CDT MON OCT 6 2025  
 
THE MID-LEVEL TROUGH ACROSS THE NORTHERN US BORDER WILL CONTINUE TO  
PROGRESS EAST DURING THE MID-WEEK PERIOD, ALLOWING A MID-LEVEL RIDGE  
TO BUILD INTO THE REGION IN ITS WAKE. GUIDANCE INDICATES THIS RIDGE  
WILL NOT BE PARTICULARLY STRONG AS IT BUILDS INTO THE REGION  
WEDNESDAY, AND THERE IS THE POTENTIAL FOR SHORTWAVE DISTURBANCES TO  
MOVE THROUGH THE FLOW INTO THE MID-MISSISSIPPI VALLEY. WHILE  
CONFIDENCE IN ANY ONE DISTURBANCE BEING ABLE TO SQUEAK SOME RAIN OUT  
OF THE DRIER POST-FRONTAL AIR IS LOW, I CAN'T RULE IT OUT. THE RIDGE  
PERSISTS INTO THE WEEKEND, AND WILL DOMINATE OUR SENSIBLE WEATHER IN  
ONE SHAPE OR FORM.  
 
WHILE YESTERDAY'S ENSEMBLE GUIDANCE WAS HIGHLIGHTING TWO SCENARIOS  
FOR THE EVOLUTION OF THE MID-LEVEL PATTERN, TODAY'S GUIDANCE IS  
SUSPICIOUSLY UNDER-DISPERSED. CONFIDENCE IS LOW IN WHERE THE AXIS  
OF THE RIDGE WILL FORM MID-WEEK AND HOW IT WILL SHIFT OVER THE  
REMAINDER OF THE WEEK AND INTO THE WEEKEND. THIS RESULTS IN LOW  
CONFIDENCE IN THE TEMPERATURE FORECAST BEYOND THURSDAY OR SO. A  
MORE EASTWARD RIDGE AXIS WILL PUT US BACK IN SOUTHWESTERLY FLOW,  
RESULTING IN A RETURN TO TEMPERATURES IN THE 80S, ALL THINGS  
CONSIDERED. IF THE RIDGE AXIS STAYS TO THE WEST OF US,  
TEMPERATURES WILL BE COOLER THAN THE PAST SEVERAL DAYS, THOUGH TO  
WHAT DEGREE REMAINS UNCERTAIN.  
 
DELIA  
 

 
   
AVIATION
 
(FOR THE 12Z TAFS THROUGH 12Z TUESDAY MORNING)  
ISSUED AT 557 AM CDT MON OCT 6 2025  
 
VFR CONDITIONS LARGELY PREVAIL AT MOST TERMINALS, EXCEPT FOR KSUS  
AND KCPS WHERE SOME INTERMITTENT MVFR FOG HAS DEVELOPED. THE MAIN  
THREAT TO THE TERMINALS WILL BE A COLD FRONT APPROACHING FROM THE  
NORTHWEST AND A SURGE OF MOISTURE FROM THE SOUTHEAST, BOTH LEADING  
TO LOWERING CIGS AND INCREASED RAIN CHANCES TONIGHT. BEFORE THAT,  
A LOW (LESS THAN 30% CHANCE) FOR SHOWERS AND A FEW THUNDERSTORMS  
WILL THREATEN THE TERMINALS. THAT SAID, WITH NO FORCING MECHANISM  
IN PLACE TO FOCUS THIS CONVECTION, THE THREAT AT ANY ONE TERMINAL  
IS TOO LOW TO MENTION IN THE TAF.  
 
THIS EVENING AS THE TWO SYSTEMS IMPINGE ON THE MID-MISSISSIPPI  
VALLEY, CIGS WILL BEGIN TO FALL. WHILE PERIODS OF MVFR CONDITIONS  
LOOK LIKELY AT THE ST. LOUIS TERMINALS AND KUIN, THESE CONDITIONS  
PROBABLY WILL NOT BE WIDESPREAD OR LONG-LASTING. CONDITIONS IN  
CENTRAL MISSOURI ARE MORE UNCERTAIN, AS THESE TERMINALS ARE  
FURTHEST FROM THE LOW-LEVEL MOISTURE. BEYOND THE TAF PERIOD,  
CONDITIONS WILL GRADUALLY IMPROVE THROUGH TUESDAY AS THE COLD  
FRONT PASSES THROUGH THE REGION.  
 
MRB  
 

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

 
 

 
 
WFO LSX  
 
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