694  
FXUS63 KLSX 301128  
AFDLSX  
 
AREA FORECAST DISCUSSION...UPDATED AVIATION  
NATIONAL WEATHER SERVICE SAINT LOUIS MO  
628 AM CDT WED APR 30 2025  
   
KEY MESSAGES
 
 
- SHOWERS AND THUNDERSTORMS REMAIN IN THE FORECAST THROUGH  
THURSDAY. ALTHOUGH A FEW STRONG TO SEVERE STORMS CANNOT BE  
RULED OUT THROUGH THE NEXT 36 HOURS, THE GREATEST CHANCE IS THIS  
EVENING.  
 
- DRY AND SEASONABLY COOL WEATHER SETS UP A BEAUTIFUL WEEKEND.  
 

 
   
SHORT TERM
 
(THROUGH LATE THURSDAY AFTERNOON)  
ISSUED AT 240 AM CDT WED APR 30 2025  
 
AT THE BIG PICTURE, A TROUGH IS CURRENTLY SITUATED NEAR THE FOUR  
CORNERS REGION OF THE DESERT SOUTHWEST WHILE A BROAD, LOW AMPLITUDE  
RIDGE EXISTS ACROSS THE SOUTHEAST US HAVING BEEN RECENTLY PUSHED  
BACK BY A FAST MOVING NORTHERN STREAM TROUGH NOW IN NEW ENGLAND.  
AT THE SURFACE, A COLD FRONT HAS PUSHED SOUTHWARD ACROSS THE  
CENTRAL US INCLUDING OUR ENTIRE FORECAST AREA IN THE WAKE OF THE  
NORTHERN STREAM TROUGH. HOWEVER, MOISTURE CONTINUES TO ADVECT  
NORTHWARD THROUGH THE SOUTHERN PLAINS AHEAD OF THE SOUTHWEST  
TROUGH. THIS HAS LED TO THE DEVELOPMENT OF MORE WIDESPREAD  
THUNDERSTORMS ACROSS OKLAHOMA OVERNIGHT NEAR WHERE THIS MOIST  
ADVECTION INTERSECTS THE FRONTAL BOUNDARY. THESE STORMS HAVE  
ALREADY BEGUN TO ORGANIZE INTO AN MCS WHICH WILL MOVE OFF TO THE  
NORTHEAST THROUGH MISSOURI TODAY. THIS MCS IS EXPECTED TO OUTRUN  
ITS SOURCE OF LOW LEVEL MOISTURE AND INSTABILITY AS IT TRACKS  
NORTH OF THE FRONT, GRADUALLY WEAKENING AS IT MOVES THROUGH OUR  
FORECAST AREA DURING THE MORNING HOURS. FLOW WITHIN AND AROUND THE  
MCS ITSELF WILL LIKELY PULL IN GREATER INSTABILITY JUST AHEAD OF  
IT, BUT THIS IS EXPECTED TO BE ELEVATED IN NATURE AS THE SURFACE  
FRONT ITSELF TAKES LONGER TO REACT AND BUCKLE BACK NORTHWARD  
TODAY. SO CURRENT THINKING IS THAT THIS MCS WILL WEAKEN AND POSE A  
LIMITED SEVERE WEATHER THREAT FOR OUR AREA. HOWEVER, THIS COULD  
CHANGE IF BETTER SURFACE BASED INSTABILITY IS ABLE TO DEVELOP  
AHEAD OF IT THIS MORNING.  
 
AS THE SOUTHWESTERN TROUGH MOVES OUT INTO THE PLAINS TODAY IT WILL  
STRENGTHEN THE LOW LEVEL MOIST SOUTHERLY FLOW AHEAD OF IT,  
TRIGGERING ANOTHER ROUND OF CONVECTION OVER OKLAHOMA. THIS AGAIN IS  
LIKELY TO ORGANIZE INTO A BROADER MCS AND PUSH NORTHEASTWARD INTO  
OUR FORECAST AREA THIS EVENING INTO THE EARLY OVERNIGHT HOURS. BY  
THIS TIME, THE SURFACE FRONT WILL HAVE PUSHED FURTHER NORTHWARD  
OPENING MORE OF THE FORECAST AREA UP TO SOME SURFACE BASED  
INSTABILITY ENABLING THIS MCS TO MAINTAIN ITS STRENGTH LONGER. WIND  
SHEAR WILL BE INCREASING AS WELL AS THE UPPER TROUGH APPROACHES, SO  
IT IS LIKELY THAT THIS REPRESENTS OUR GREATEST THREAT FOR SEVERE  
WEATHER. DAMAGING WINDS WILL BE THE PRIMARY THREAT, BUT THERE MAY BE  
ENOUGH LOW LEVEL WIND SHEAR FOR A FEW QLCS TORNADOES AS WELL. THE  
BIGGEST LIMITING FACTOR WILL BE SURFACE BASED INSTABILITY WHICH WILL  
BE ON A DIURNAL DOWNWARD TREND.  
 
WHILE THIS NEXT MCS MOVES NORTHEAST AND OUT OF OUR FORECAST AREA  
EARLY THURSDAY MORNING, SURFACE LOW PRESSURE WILL BE TRACKING  
THROUGH NORTHEAST MISSOURI IN RESPONSE TO THE ARRIVAL OF THE UPPER  
TROUGH. THIS WILL HAVE THE EFFECT OF HALTING THE NORTHWARD  
ADVANCE OF THE WARM FRONT AND SENDING IT BACK SOUTHEAST AS A COLD  
FRONT DURING THE DAY ON THURSDAY. ADDITIONAL SHOWER AND  
THUNDERSTORM ACTIVITY IS EXPECTED AS THE TROUGH MOVES THROUGH,  
PRIMARILY AHEAD OF THE SURFACE COLD FRONT. WIND SHEAR WILL BE  
WEAKER NEAR THE CORE OF THE UPPER TROUGH, AND IT'S UNCLEAR HOW  
MUCH INSTABILITY WILL BE ABLE TO REDEVELOP AHEAD OF THE FRONT IN  
THE WAKE OF THE EARLY MORNING MCS. THESE FACTORS LEAD TO A MUCH  
MORE LIMITED SEVERE WEATHER THREAT WITH THIS ROUND. IN FACT,  
LATEST CAMS HAVE ANY SHOWER AND THUNDERSTORM ACTIVITY ON THURSDAY  
MUCH MORE ISOLATED IN NATURE AND THE SPC OUTLOOK HAS SHIFTED THE  
CORE OF THE SEVERE THREAT TO THE EAST OF OUR FORECAST AREA.  
 
ONE FINAL NOTE ON TOTAL RAINFALL AMOUNTS. THERE ARE LIKELY TO BE  
SWATHS OF 1 TO 2 OR PERHAPS EVEN 3 INCHES OF RAIN WITH EACH OF THE  
BROADER CONVECTIVE COMPLEXES THAT MOVE THROUGH THE REGION THIS  
MORNING THROUGH TONIGHT. EACH OF THESE SWATHS WILL BE RELATIVELY  
NARROW IN WIDTH, WITH A BROADER AREA OF MORE MODERATE RAINFALL OF  
0.5 TO 1 INCHES. WHILE 1 TO 2 INCHES OVER THE COURSE OF A FEW HOURS  
IS NOT LIKELY TO CAUSE FLASH FLOODING IN GENERAL, THIS ASSESSMENT  
COULD CHANGE IF THESE SWATHS MOVE ACROSS AREAS ALREADY SIGNIFICANTLY  
MOISTENED BY EARLIER RAINFALL. IF ANY AREAS ARE AFFECTED BY THE MORE  
SIGNIFICANT SWATHS OF RAINFALL FROM BOTH ROUNDS, THEN A GREATER  
FLASH FLOOD THREAT WILL RESULT. AS FAR AS RIVER FLOODING, THE  
COMBINED EFFECT OF SEVERAL DAYS OF RAINFALL WILL LEAD TO RISES ON  
NEARLY ALL CREEKS AND RIVERS ACROSS THE REGION. THE DEGREE OF THE  
RISES ON EACH RIVER WILL BE DETERMINED BY WHERE THOSE SWATHS OF  
HEAVY RAIN FALL. THERE IS A COMPARABLY GREATER CHANCE THAT A FEW  
RIVERS WILL RISE TO FLOOD STAGE IN THE COMING DAYS AS ALL OF THIS  
WATER HAS TO GO SOMEWHERE AND WILL GRADUALLY COLLECT INTO THE LARGER  
RIVERS OVER THE COURSE OF HOURS TO DAYS. AT THIS TIME, CONFIDENCE IN  
FLASH FLOODING OR RIVER FLOODING IN ANY PARTICULAR AREA IS TOO LOW  
FOR A FLOOD WATCH.  
 
KIMBLE  
 

 
   
LONG TERM
 
(THURSDAY NIGHT THROUGH TUESDAY)  
ISSUED AT 240 AM CDT WED APR 30 2025  
 
THURSDAY'S COLD FRONT SENDS A COOLER AND DRIER AIR MASS INTO THE  
AREA. DEWPOINTS FALL INTO THE 40S ON FRIDAY WHILE TEMPERATURES REACH  
THE 60S TO LOW 70S, NEAR OR SLIGHTLY BELOW NORMAL FOR THIS TIME OF  
YEAR. A SECONDARY TROUGH DROPPING SOUTH FROM THE NORTHERN STREAM  
BRINGS RENEWED COLD ADVECTION AND ONE MORE CHANCE OF SHOWERS. THESE  
SHOWERS ON FRIDAY WILL BE DRIVEN BY COLD ADVECTION ALOFT RATHER THAN  
BY MOIST ADVECTION IN THE LOW LEVELS. AS A RESULT, INSTABILITY WILL  
BE MEAGER AND MOISTURE QUITE LIMITED. RAINFALL AMOUNTS FROM THIS  
WILL BE MINOR, WITH ENSEMBLE PROBABILITY OF 0.1 INCH OF RAINFALL  
PEAKING AT ONLY ABOUT 20 PERCENT IN OUR AREA ON FRIDAY. WHILE WE  
CANNOT RULE OUT A FEW STRIKES OF LIGHTNING, WE DO NOT ANTICIPATE  
SEVERE WEATHER.  
 
MOST GUIDANCE HAS FRIDAY'S TROUGH EXITING QUICKLY TO THE EAST,  
REPLACED BY RIDGING DOWNSTREAM OF A DEVELOPING WESTERN US TROUGH.  
HOWEVER, CLUSTER ANALYSIS SHOWS THAT SOME GUIDANCE, LED BY THE ECMWF  
AND CMC, ACTUALLY PULL FRIDAY'S TROUGH SO FAR SOUTH THAT IT GETS CUT  
OFF BENEATH THE DEVELOPING RIDGE AND LINGERS OVER THE OHIO VALLEY  
THIS WEEKEND AND RIGHT INTO NEXT WEEK. SO WHILE THE GENERAL TREND  
FAVORS DRY WEATHER, RIDGING, AND AN EVENTUAL WARM UP, A LINGERING  
CUT OFF LOW COULD SPOIL THAT SOMEWHAT. THE PRACTICAL DIFFERENCE  
WOULD BE LINGERING 60S AND 70S VS A RETURN TO THE 80S. THERE WILL  
ALSO BE SOME CHANCES FOR LIGHT SHOWERS IN THE VICINITY OF THE CUT  
OFF LOW WHILE RIDGING WOULD FAVOR MORE SUNNY CONDITIONS.  
 
DESPITE THE UNCERTAINTY IN THE UPPER AIR FLOW PATTERN MENTIONED  
ABOVE, ALL SCENARIOS POINT TO GULF MOISTURE REMAINING CUT OFF AND  
MOISTURE RETURN FOCUSED OVER THE WESTERN HIGH PLAINS. SO WE'RE  
NOT EXPECTING ANY SIGNIFICANT PRECIPITATION FOR SEVERAL DAYS, AT  
LEAST UNTIL THAT WESTERN TROUGH BEGINS TO MOVE EAST LATE IN THE  
WEEK.  
 
KIMBLE  
 

 
   
AVIATION
 
(FOR THE 12Z TAFS THROUGH 12Z THURSDAY MORNING)  
ISSUED AT 624 AM CDT WED APR 30 2025  
 
IT'S A RATHER COMPLEX FORECAST TODAY AND TONIGHT. A DYING  
THUNDERSTORM COMPLEX IS MOVING ACROSS THE REGION THIS MORNING.  
IT'S NOT CERTAIN WHETHER THUNDER WILL OCCUR AT ANY TAF SITE, BUT  
THIS SEEMS MOST LIKELY IN THE SOUTHEAST PART OF THE ST LOUIS  
METRO IN THE NEXT FEW HOURS. WE DO EXPECT A BREAK IN THE RAIN  
AFTER THIS MOVES THROUGH, BUT SOME LOWER CEILINGS ARE LURKING  
NEARBY AND ARE LIKELY TO KEEP CONDITIONS MVFR OR IFR FOR MUCH OF  
THE MORNING INTO THE AFTERNOON AT MOST SITES. A WARM FRONT LIFTING  
NORTH TODAY MAY BRING SOME CLEARING TO VFR AT CENTRAL MO AS WELL  
AS THE ST LOUIS METRO AROUND MIDDAY OR THE EARLY AFTERNOON. BUT  
ANOTHER ROUND OF THUNDERSTORMS IS EXPECTED TONIGHT, WITH A GREATER  
CHANCE OF IMPACTING BOTH CENTRAL MO AS WELL AS ST LOUIS. A RETURN  
TO LOWER CEILINGS IS LIKELY AFTER THIS RAIN ENDS. FURTHER NORTH AT  
QUINCY, LOWER CEILINGS HAVE YET TO MATERIALIZE AND MAY NOT DO SO  
FOR SOME TIME. QUINCY IS ALSO THE LEAST LIKELY TO SEE  
THUNDERSTORMS OF ANY TAF SITE.  
 
KIMBLE  
 

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

 
 

 
 
WFO LSX  
 
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