768  
FXUS63 KLSX 060342  
AFDLSX  
 
AREA FORECAST DISCUSSION...UPDATED AVIATION  
NATIONAL WEATHER SERVICE SAINT LOUIS MO  
1042 PM CDT SAT JUL 5 2025  
   
KEY MESSAGES
 
 
- WIDELY SCATTERED SHOWERS (20-30% CHANCE) AND A FEW SPORADIC  
THUNDERSTORMS (10% CHANCE OR LESS) WILL PERSIST THE REMAINDER  
OF THE AFTERNOON, WITH A FEW POSSIBLE OVERNIGHT AS WELL.  
 
- INCREASED CHANCES (30 TO 60%) FOR SHOWERS AND THUNDERSTORMS  
EXIST TOMORROW AFTERNOON, WITH A FEW MICROBURSTS AND HEAVY  
DOWNPOURS POSSIBLE. WHILE WE DON'T EXPECT THOSE HAZARDS TO BE  
WIDESPREAD, SOME MINOR WIND DAMAGE AND LOCALIZED FLOODING CAN'T  
BE RULED OUT.  
 
- A TYPICAL SUMMERTIME PATTERN WILL PERSIST FOR THE NEXT WEEK,  
WITH REPEATED CHANCES FOR SCATTERED, MOSTLY WEAK SHOWERS AND  
THUNDERSTORMS ALMOST DAILY AND NEAR AVERAGE TEMPERATURES.  
 

 
   
SHORT TERM
 
(THROUGH LATE SUNDAY NIGHT)  
ISSUED AT 120 PM CDT SAT JUL 5 2025  
 
THE PRIMARY CONCERN FOR THE REMAINDER OF THE DAY AND INTO  
TOMORROW CONTINUES TO BE THE POTENTIAL FOR SHOWERS AND  
THUNDERSTORMS, ALONG WITH POTENTIALLY SOME ISOLATED DOWNBURSTS AND  
HEAVY RAIN RATES TOMORROW AFTERNOON.  
 
AS WE MOVE PAST MIDDAY, SOME WEAK SHOWERS HAVE ALREADY BROKEN  
THROUGH A VERY WEAK CAP ACROSS PARTS OF CENTRAL MISSOURI, WITH  
SOME MORE ROBUST THUNDERSTORM ACTIVITY JUST TO THE NORTHWEST OF  
THERE. THESE STORMS ARE LIKELY BEING TRIGGERED BY A COMBINATION OF  
AFTERNOON HEATING AND COOLING ALOFT FROM A VERY SUBTLE MID/UPPER  
LEVEL SHORTWAVE EVIDENT ON WATER VAPOR IMAGERY. INSTABILITY IS  
ALREADY MODERATE (1000-1500 J/KG ML CAPE) AND WILL LIKELY INCREASE  
ANOTHER 500 J/KG OR SO OVER THE NEXT FEW HOURS. HOWEVER, WIND  
SHEAR IS VERY MEAGER, WITH EFFECTIVE SHEAR VALUES OF ONLY AROUND  
15 KT OR SO. AS A RESULT, THIS ACTIVITY HAS NOT BEEN PARTICULARLY  
STRONG YET, AND OUR LOCAL CELLS HAVE NOT PRODUCED LIGHTNING AS OF  
12:30. HOWEVER, IT SHOULD BE NOTED THAT A SLIGHTLY MORE  
SUBSTANTIAL BOWING SEGMENT HAS PRODUCED A BIT OF LIGHTNING JUST TO  
THE NORTHWEST, AND WE CAN'T RULE OUT A FEW STRIKES OVER THE NEXT  
SEVERAL HOURS. OTHERWISE THOUGH, STRONG/SEVERE STORMS ARE NOT  
EXPECTED, ASIDE FROM A LIMITED POTENTIAL FOR A MICROBURST.  
 
THIS INITIAL ACTIVITY IS LIKELY TO DIMINISH AS THE SUN SETS, BUT  
ANOTHER ROUND OF DECAYING SHOWERS AND THUNDERSTORMS WILL BE POSSIBLE  
OVERNIGHT AS ACTIVITY FORMING ALONG AN UPSTREAM COLD FRONT SINKS  
INTO OUR AREA. LATEST MODEL TRENDS SUGGEST THAT THIS ACTIVITY WILL  
BE DIMINISHING AS IT ARRIVES, LIKELY DUE TO THE LOSS OF  
INSTABILITY AND CONTINUED VERY WEAK SHEAR. WHILE WE WILL LIKELY  
SEE AT LEAST SOME SEMBLANCE OF SHOWERS/STORMS OVERNIGHT, IMPACTS  
ARE EXPECTED TO BE MINIMAL.  
 
BY TOMORROW AFTERNOON, THE AFOREMENTIONED WEAK "COLD" FRONT WILL  
SETTLE SOMEWHERE ACROSS THE AREA, LIKELY NEAR OR JUST NORTH OF THE I-  
70 CORRIDOR BY MID AFTERNOON. THIS BOUNDARY IS LIKELY TO PROVIDE A  
MORE FOCUSED FORCING MECHANISM FOR CONVECTION IN A VERY WEAKLY  
CAPPED ENVIRONMENT, ALTHOUGH THERE MAY BE EVEN LESS UPPER LEVEL  
SUPPORT THAN TODAY. MEANWHILE, MOISTURE CONTENT IS LIKELY TO  
INCREASE, WITH PRECIPITABLE WATER VALUES SURGING TO BETWEEN 1.8 AND  
2.2 INCHES, PER THE HREF. MEANWHILE, MODERATE INSTABILITY WILL  
REMAIN IN PLACE, PERHAPS REACHING AS HIGH AS 2000 J/KG OF SBCAPE  
ALONG THE FRONT BY LATE AFTERNOON. MODEL SOUNDINGS ALSO INDICATE  
SHALLOW INVERTED V SOUNDINGS WITH STEEP LOW LEVEL LAPSE RATES, ALONG  
WITH SOME POTENTIAL FOR MID-LEVEL DRY AIR ENTRAINMENT THAT COULD  
ENHANCE THE DOWNDRAFT POTENTIAL. AS SUCH, IT REMAINS POSSIBLE THAT  
WE COULD SEE A FEW MICROBURSTS WITH THIS ACTIVITY, ALTHOUGH THE EVEN  
WEAKER EFFECTIVE SHEAR (10KT OR EVEN LESS) WILL LIKELY PREVENT  
STORMS FROM BECOMING ORGANIZED. MEANWHILE, BURSTS OF HEAVY RAIN WILL  
ALSO BE POSSIBLE, AND WE CAN'T RULE OUT VERY LOCALIZED FLOODING IF  
CELLS CAN LAST FOR MORE THAN AN HOUR OR SO IN ONE SPOT. THEY WON'T  
BE MOVING VERY QUICKLY AND RAIN RATES MAY BE HIGH, BUT WITH SUCH  
WEAK WIND SHEAR IT REMAINS TO BE SEEN WHETHER UPDRAFTS WILL BE ABLE  
TO MAINTAIN THEMSELVES BEFORE THEY GET CUT OFF BY THEIR OWN OUTFLOW.  
 
THIS ACTIVITY IS LIKELY TO SLOWLY DRIFT TO THE SOUTHEAST WITH THE  
FRONT DURING THE EVENING AND DIMINISH IN COVERAGE, LARGELY DRIVEN  
BY THEIR OWN OUTFLOW, BUT A FEW SHOWERS MAY LINGER THROUGH THE NIGHT.  
 
BRC  
 

 
   
LONG TERM
 
(MONDAY THROUGH NEXT SATURDAY)  
ISSUED AT 120 PM CDT SAT JUL 5 2025  
 
FROM MONDAY ONWARDS, A STAGNANT PATTERN AND THE PREVIOUSLY MENTIONED  
WEAK FRONTAL BOUNDARY ARE LIKELY TO RESULT IN ADDITIONAL CHANCES FOR  
SCATTERED SHOWERS AND WEAK THUNDERSTORMS ALMOST EVERY DAY THROUGH  
THE END OF THE WORK WEEK. WHILE THE AFTERNOONS WILL LIKELY BE  
FAVORED ON MOST DAYS, THAT MAY NOT ALWAYS BE THE CASE EVERY DAY.  
 
FIRST, THE STALLED FRONT IS LIKELY TO REMAIN ACROSS THE AREA MONDAY,  
ALTHOUGH THERE IS A LOT OF UNCERTAINTY REGARDING HOW THIS BOUNDARY  
WILL BE AUGMENTED BY OUTFLOW FROM SUNDAY'S STORMS. IN ANY CASE,  
ANOTHER ROUND OF SCATTERED SHOWERS AND STORMS IS LIKELY TO DEVELOP  
MONDAY AFTERNOON WHEREVER IT SETTLES, WITH SIMILAR POTENTIAL  
HAZARDS. ENSEMBLE GUIDANCE SUGGESTS THAT THIS IS MOST LIKELY TO  
OCCUR ALONG AND SOUTH OF I-70.  
 
BETWEEN TUESDAY AND WEDNESDAY, A SLIGHTLY MORE SUBSTANTIAL  
SHORTWAVE MAY MOVE ACROSS THE UPPER MISSISSIPPI VALLEY REGION,  
TRIGGERING MORE WIDESPREAD AND SLIGHTLY MORE ORGANIZED STORMS TO  
OUR NORTHWEST TUESDAY AFTERNOON. WHILE WE MAY SEE ANOTHER ROUND OF  
WEAK AFTERNOON POP-UP SHOWERS LOCALLY DURING THE AFTERNOON, THE  
BETTER CHANCES MAY ACTUALLY BE OVERNIGHT THROUGH WEDNESDAY  
MORNING. GIVEN THAT THIS IS STILL SEVERAL DAYS AWAY AND STILL  
RATHER WEAKLY FORCED ENVIRONMENT, THIS TIMING REMAINS VERY  
TENUOUS.  
 
BEYOND WEDNESDAY MORNING, CONFIDENCE IN THE DAY-TO-DAY DETAILS  
REMAINS LOW, BUT THERE IS NOT MUCH TO SUGGEST THAT THE PATTERN WILL  
SIGNIFICANTLY CHANGE OVER THE NEXT WEEK. LREF ENSEMBLE MEAN 500MB  
FORECASTS SUGGESTS THAT THERE MAY BE A SLIGHT TREND TOWARD LOWERING  
HEIGHTS AND WEAK TROUGHING LATE IN THE WEEK, WHICH MAY OPEN THE DOOR  
FOR ADDITIONAL SUBTLE SHORTWAVES TO MOVE THROUGH THE AREA, AND THESE  
MAY PROVIDE SOME MODEST FORCING ENHANCEMENTS FOR PRECIPITATION. AS  
SUCH, WE WILL MAINTAIN THE POTENTIAL FOR SCATTERED SHOWERS AND  
THUNDERSTORMS EACH DAY THROUGH SATURDAY.  
 
MEANWHILE, WITH LITTLE IN THE WAY OF SYNOPTIC COLD FRONTS OR  
SUBSTANTIAL CHANGES IN THE OVERALL PATTERN FOR THE FORESEEABLE  
FUTURE, THE TEMPERATURE FORECAST REMAINS RELATIVELY STEADY FOR THE  
NEXT WEEK, AND RIGHT AROUND SEASONAL AVERAGES. THIS WILL VARY LIKELY  
VARY FROM DAY TO DAY AND FROM LOCATION TO LOCATION DEPENDING ON HOW  
SHOWERS AND CLOUD COVER EVOLVE, BUT MOST SHOULD EXPECT TO SEE  
TYPICAL EARLY JULY TEMPERATURES AND MODERATE TO HIGH HUMIDITY FOR  
THE NEXT WEEK.  
 
BRC  
 

 
   
AVIATION
 
(FOR THE 06Z TAFS THROUGH 06Z SUNDAY NIGHT)  
ISSUED AT 1035 PM CDT SAT JUL 5 2025  
 
SCATTERED THUNDERSTORMS ARE EXPECTED TO ENTER NORTHEAST MISSOURI  
SHORTLY, BUT ARE FORECAST TO GRADUALLY WEAKEN AND DISSIPATE  
OVERNIGHT. WHILE THE THREAT FOR THUNDERSTORMS IS NOT ZERO VERY LATE  
TONIGHT INTO EARLY SUNDAY MORNING, IT IS VERY LOW. COVERAGE OF  
STORMS SHOULD INCREASE JUST AFTER MIDDAY ON SUNDAY, WITH THE BEST  
CHANCES FROM THE ST. LOUIS METRO AND POINTS SOUTH. ADDED A TEMPO  
AT THE METRO TERMINALS FOR THUNDERSTORMS, ROUGHLY BETWEEN 19 AND  
23 UTC. ANY STORM THAT DOES DIRECTLY IMPACT A SITE WILL BE CAPABLE  
OF HEAVY DOWNPOURS/REDUCED VISIBILITIES AND POTENTIALLY GUSTY  
WINDS.  
 
GOSSELIN  
 

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

 
 

 
 
WFO LSX  
 
CLICK HERE TO GO TO PREVIOUS BULLETINS.

The Nexlab MO Page
The Nexlab IL Page Main Text Page