647  
FXUS63 KLSX 301116  
AFDLSX  
 
AREA FORECAST DISCUSSION...UPDATED AVIATION  
NATIONAL WEATHER SERVICE SAINT LOUIS MO  
616 AM CDT WED JUL 30 2025  
   
KEY MESSAGES
 
 
- A COLD FRONT WILL PUSH THROUGH THE REGION TODAY BRINGING HEAT RELIEF  
TO AREAS GENERALLY NORTH OF I-70. THE HEATWAVE WILL END  
ENTIRELY BY TONIGHT.  
 
- THE COLD FRONT WILL ALSO BRING A MARGINAL THREAT FOR STRONG TO  
SEVERE THUNDERSTORMS TO THE REGION THIS AFTERNOON INTO EVENING.  
DAMAGING WINDS AND ISOLATED FLASH FLOODING WILL BE THE PRIMARY  
HAZARDS.  
 

 
   
SHORT TERM
 
(THROUGH LATE THURSDAY AFTERNOON)  
ISSUED AT 337 AM CDT WED JUL 30 2025  
 
AN MCS CURRENTLY TRAVERSING IOWA WILL SINK SOUTHEAST THROUGH THIS  
MORNING, ENTERING NORTHEAST MISSOURI AND WEST-CENTRAL ILLINOIS  
SHORTLY AFTER SUNRISE. AS IT PASSES THROUGH THESE AREAS, THE MCS IS  
EXPECTED TO LAY OUT AN OUTFLOW BOUNDARY WHICH MAY ACT AS A CATALYST  
FOR CONVECTION THIS AFTERNOON DEPENDING ON HOW STRONG SURFACE  
CONVERGENCE IS ALONG IT. HI-RES GUIDANCE VARIES WITH THIS, WITH EACH  
MODEL SHOWING DIFFERING AMOUNTS OF COVERAGE IF IT HAS CONVECTIVE  
INITIATION AT ALL. THE PRESENCE OF THUNDERSTORMS IS MORE CERTAIN  
ALONG A COLD FRONT THAT WILL BE DIPPING SOUTH THROUGH THE AREA LATE  
THIS AFTERNOON THROUGH TONIGHT. THESE THUNDERSTORMS WILL BE ENTERING  
AN ENVIRONMENT CHARACTERIZED BY 1500-2000 J/KG OF SBCAPE AND 25-35  
KTS OF 0-6 KM BULK SHEAR. THESE CONDITIONS WILL BE SUFFICIENT FOR  
THUNDERSTORM ORGANIZATION, WITH A FEW STRONG TO SEVERE THUNDERSTORMS  
EXPECTED. DAMAGING WINDS WILL BE THE PRIMARY THREAT IN ANY  
THUNDERSTORMS THAT DO BECOME SEVERE, AND HEAVY RAIN IS EXPECTED IN  
ANY THUNDERSTORMS PERIOD. BULK SHEAR VECTORS NEARLY PARALLEL TO THE  
COLD FRONT AND PWATS APPROACHING 2" BRING THE POTENTIAL FOR FLASH  
FLOODING INTO QUESTION. IT IS POSSIBLE GIVEN THE POTENTIAL FOR  
TRAINING AND THE HIGH RAIN RATES. HOWEVER, THUNDERSTORMS ARE  
EXPECTED TO BE PROGRESSIVE, SO THEY SHOULDN'T SIT OVER A SINGLE  
LOCATION FOR TOO LONG. THE ABSENCE OF A NOCTURNAL LLJ TONIGHT WILL  
ALSO BE UNSUPPORTIVE FOR CONTINUOUS CONVECTIVE DEVELOPMENT ALONG THE  
BOUNDARY, WHICH LOWERS THE POTENTIAL FOR TRAINING AND WIDESPREAD  
FLASH FLOODING IMPACTS. I BELIEVE FLASH FLOODING WILL BE LOCALIZED  
TO AREAS THAT 1) EXPERIENCE MULTIPLE THUNDERSTORMS AND/OR 2) HAVE  
HAD AN ABUNDANCE OF RAINFALL RECENTLY AND ARE PRIMED FOR FLOODING.  
THUNDERSTORMS WILL SLOWLY DIMINISH OVERNIGHT. REDEVELOPMENT IS  
LIKELY SOUTH OF I-70 TOMORROW AS THE LAST OF THE MID-LEVEL FORCING  
INTERACTS WITH THE EXITING FRONT. SEVERE WEATHER IS NOT EXPECTED.  
 
FOR LOCATIONS GENERALLY SOUTH OF I-70, TODAY'S TEMPERATURE FORECAST  
WILL FOLLOW THE STATUS QUO. DANGEROUS HEAT INDEX VALUES OF UP TO 110  
DEGREES ARE EXPECTED YET AGAIN, THANKFULLY FOR THE FINAL TIME DURING  
THIS HOT STRETCH. TO THE NORTH, THE ARRIVAL OF THE DECAYING MCS THIS  
MORNING AND COLD FRONT LATER TODAY WILL KEEP THE HEAT DAMPENED  
COMPARED TO DAYS PAST WITH HEAT INDEX VALUES LANDING IN THE 90S.  
TOMORROW WILL BE OUR FIRST DAY OF WIDESPREAD HEAT RELIEF AS MUCH  
COOLER AIR FLOODS INTO THE REGION. LOCATIONS NORTH OF I-70 ARE  
FORECAST TO REMAIN IN THE 70S FOR HIGHS, WHICH IS VERY CLOSE TO WHAT  
THEIR LOWS HAVE BEEN FOR THE PAST WEEK. HIGHS IN THE 80S ARE  
FORECAST SOUTH OF I-70 WHERE THE COOLER AIR WILL NOT HAVE FULLY  
INFILTRATED.  
 
JAJA  
 

 
   
LONG TERM
 
(THURSDAY NIGHT THROUGH TUESDAY)  
ISSUED AT 337 AM CDT WED JUL 30 2025  
 
THE INFLUENCE OF SURFACE HIGH PRESSURE WILL BE THE DOMINANT FORCE  
FOR OUR SENSIBLE WEATHER FROM FRIDAY THROUGH SUNDAY. THESE DAYS WILL  
BE DRY AS A RESULT WITH HIGHS IN THE 70S TO LOW 80S. MORNING LOWS  
WILL BE BRISK COMPARED TO WHAT WE'VE BECOME USED TO. PORTIONS OF  
NORTHEAST MISSOURI WILL FALL INTO THE MID-50S EACH NIGHT, WITH AREAS  
TO THE SOUTH RANGING FROM THE LOW TO MID-60S FOR LOWS.  
 
THE PATTERN CHANGES EARLY NEXT WEEK AS THE SURFACE HIGH EXITS OFF TO  
THE EASTERN US. SOUTHERLY FLOW WILL RETURN, AND TEMPERATURES WILL  
GRADUALLY RISE THROUGH THE WEEK. ALOFT, A SHORTWAVE IS FORECAST TO  
SLIDE THROUGH THE MID-MISSISSIPPI VALLEY SOMETIME IN THE EARLY WEEK,  
BRINGING RAIN CHANCES BACK INTO THE FORECAST. THE ONLY SIMILARITY  
AMONG GUIDANCE CONCERNING THE SHORTWAVE IS THAT THEY ALL SHOW ONE,  
SO ANY DETAILS REMAIN UNCERTAIN AT THIS TIME.  
 
JAJA  
 

 
   
AVIATION
 
(FOR THE 12Z TAFS THROUGH 12Z THURSDAY MORNING)  
ISSUED AT 607 AM CDT WED JUL 30 2025  
 
A THUNDERSTORM COMPLEX WILL MOVE INTO NORTHEAST MO AND WEST-  
CENTRAL IL AT THE START OF THE TAF PERIOD. GUSTY WINDS OF AROUND  
30 KTS AND IFR CONDITIONS ARE EXPECTED ON THE FRONT EDGE OF THE  
STORM, WITH FLIGHT CONDITIONS IMPROVING AFTER THE FRONT LINE OF  
STORMS PASSES. THIS AFTERNOON, THUNDERSTORMS WILL DEVELOP ACROSS  
MUCH OF THE AREA AS A COLD FRONT PASSES. THESE THUNDERSTORMS WILL  
BE CAPABLE OF GUSTY WINDS AND IFR FLIGHT CONDITIONS AS WELL.  
EXACT TIMING ON IMPACTS AT EACH TERMINAL IS STILL UNCERTAIN AND  
WILL NEED TO BE REFINED WITH LATER UPDATES, BUT THE GENERAL  
FORECAST IS ON TRACK.  
 
OUTSIDE OF ANY THUNDERSTORMS, WINDS WILL REMAIN LIGHT AND  
VARIABLE BEFORE SLOWLY SHIFTING TO NORTHERLY LATE IN THE PERIOD.  
WIDESPREAD LOW MVFR TO IFR STRATUS WILL FILL IN BEHIND THE FRONT  
OVERNIGHT AND LAST AT LEAST THROUGH THE LATE MORNING.  
 
JAJA  
 

 
   
LSX WATCHES/WARNINGS/ADVISORIES
 
 
MO...HEAT ADVISORY UNTIL 7 PM CDT THIS EVENING FOR BOONE MO-CALLAWAY  
MO-COLE MO-CRAWFORD MO-GASCONADE MO-IRON MO-LINCOLN MO-  
MADISON MO-MONITEAU MO-MONTGOMERY MO-OSAGE MO-REYNOLDS MO-  
SAINT FRANCOIS MO-WARREN MO-WASHINGTON MO.  
 
EXTREME HEAT WARNING UNTIL 7 PM CDT THIS EVENING FOR FRANKLIN MO-  
JEFFERSON MO-SAINT CHARLES MO-SAINT LOUIS CITY MO-SAINT  
LOUIS MO-SAINTE GENEVIEVE MO.  
 
IL...HEAT ADVISORY UNTIL 7 PM CDT THIS EVENING FOR CALHOUN IL-FAYETTE  
IL-GREENE IL-JERSEY IL-MACOUPIN IL-MONTGOMERY IL.  
 
EXTREME HEAT WARNING UNTIL 7 PM CDT THIS EVENING FOR BOND IL-  
CLINTON IL-MADISON IL-MARION IL-MONROE IL-RANDOLPH IL-SAINT  
CLAIR IL-WASHINGTON IL.  
 

 
 

 
 
WFO LSX  
 
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