799  
FXUS63 KLSX 041038  
AFDLSX  
 
AREA FORECAST DISCUSSION...UPDATED AVIATION  
NATIONAL WEATHER SERVICE SAINT LOUIS MO  
538 AM CDT FRI JUL 4 2025  
   
KEY MESSAGES  
 
- WARM AND HUMID CONDITIONS ARE EXPECTED TODAY THROUGH SATURDAY.  
TEMPERATURES FALL SLIGHTLY SUNDAY INTO MONDAY AND REMAIN FAIRLY  
STEADY THROUGH NEXT WEEK.  
 
- MAINLY DRY CONDITIONS ARE EXPECTED THROUGH SATURDAY BEFORE  
CHANCES OF SHOWERS AND THUNDERSTORMS INCREASE LATE SATURDAY INTO  
SUNDAY. PROBABILITIES FOR ADDITIONAL SHOWERS AND THUNDERSTORMS  
EXTEND THROUGH THE UPCOMING WEEK.  
 
 
   
SHORT TERM  
(THROUGH LATE SATURDAY AFTERNOON)  
ISSUED AT 224 AM CDT FRI JUL 4 2025  
 
A LOOK AROUND THE REGION SHOWS THE CENTER OF SURFACE HIGH PRESSURE  
SLIDING JUST TO THE EAST OF THE LOCAL AREA. IN RESPONSE, SURFACE  
WINDS ARE VEERING OUT OF THE SOUTHEAST TO SOUTH FROM EASTERN  
MISSOURI WESTWARD THROUGH EASTERN KANSAS. THE SURFACE HIGH IS  
TRAILED BY AMPLIFIED MID/UPPER LEVEL RIDGING THAT WILL POSITION  
OVERHEAD TODAY THROUGH SATURDAY.  
 
SOUTHERLY FLOW AT THE WESTERN SIDE OF THE RIDGE IS DRAWING MOISTURE  
NORTHWARD INTO THE EASTERN PLAINS AND WILL EVENTUALLY SHIFT EASTWARD  
INTO THE LOCAL AREA IN COMING DAYS. UNTIL THEN, SUBSIDENCE WILL  
MAINTAIN DRY CONDITIONS WITH MOSTLY CLEAR TO PARTLY CLOUDY SKIES.  
EXPECT TEMPERATURES TO CLIMB INTO THE 90S AREAWIDE WITH URBAN AREAS  
SQUARELY IN THE MID-90S. HEAT INDEX VALUES WILL ONLY BE A FEW  
DEGREES WARMER THAN ACTUAL AIR TEMPERATURES, ALONG WITH AN INCREASE  
IN SURFACE FLOW. THIS MAY COUNTER THE MOISTURE SOMEWHAT, SERVING TO  
COOL THOSE OUTDOORS BETTER THAN THE CALM/VARIABLE WINDS OF THE LAST  
24 HOURS.  
 
SATURDAY IS ANOTHER WARM DAY WITH MUCH OF THE DAYLIGHT HOURS  
REMAINING DRY. LATEST DATA SUGGESTS SLIGHT CHANCES (15-20%) WILL  
NUDGE INTO THE WESTERN EDGE OF THE CWA BY MID-MORNING SATURDAY. IF  
THIS DID OCCUR, IT'S LIKELY TO BE REMNANT ACTIVITY FROM THE WEST,  
WHICH WOULD BE EXPECTED TO BE GOING THROUGH A DISSIPATING PHASE  
CONSIDERING IT BEING DURING THE DIURNAL LULL IN INSTABILITY AND  
MODEL SOUNDING SHOW AIR QUICKLY DRYING FROM WEST TO EAST. TIMING  
TOOLS SHOW THE BEST ESTIMATE FOR MEASURABLE RAINFALL WILL BE AROUND  
5 P.M. SATURDAY EVENING AND I'D SAY THIS MAY BE AT THE EARLIER STAGE  
OF POTENTIAL AS LREF SHOWS 10-30% PROBABILITIES FOR MEASURABLE  
RAINFALL.  
 
REGARDLESS OF RAINFALL, CLOUD COVER WILL BE THICKER TO THE WEST  
DURING THE DAY SATURDAY. THIS KEEPS TEMPERATURES SLIGHTLY COOLER  
FROM CENTRAL MISSOURI THROUGH WEST-CENTRAL ILLINOIS, WHERE UPPER 80S  
ARE FORECAST. 90S WILL LARGELY BE CONFINED TO SOUTHEASTERN AND EAST-  
CENTRAL MISSOURI AND SOUTHWESTERN ILLINOIS. LOWS WILL RANGE FROM THE  
UPPER 60S TO LOW-70S.  
 
MAPLES  
 
 
   
LONG TERM  
(SATURDAY NIGHT THROUGH THURSDAY)  
ISSUED AT 224 AM CDT FRI JUL 4 2025  
 
ASIDE FROM THE MODEST SPREAD IN TEMPERATURES , ENSEMBLES HAVE BEEN  
RATHER TIGHTLY CLUSTERED ALONG WITH CONSISTENCY IN DETERMINISTIC  
LONG RANGE GUIDANCE WITH RESPECT TO INCREASING RAIN CHANCES SATURDAY  
NIGHT INTO SUNDAY. THIS IS THE TIMEFRAME THAT THE UPPER LEVEL RIDGE  
OVERHEAD BEGINS TO MOVE EAST AND DEAMPLIFY AS A TRAIN OF  
TROUGHS/SHORTWAVES TRAVERSE THE NORTHERN SECTIONS OF THE LOWER 48.  
 
GUIDANCE CONTINUES TO SHOW THE FIRST IN THE SERIES OF SHORTWAVES  
MOVING INTO THE GREAT LAKES WHILE PUSHING A WEAKENING COLD FRONT  
SOUTHWARD INTO THE REGION. POTENTIAL FOR SHOWERS AND THUNDERSTORMS  
WILL INCREASE FROM NORTH TO SOUTH LATE SATURDAY INTO SUNDAY. WHAT  
INITIALLY ARRIVES IS LIKELY TO BE IN THE FORM OF SHOWERS OR  
WEAKENING CONVECTION AS SURFACE INSTABILITY DROPS IN THE OVERNIGHT  
PERIOD. SUNDAY WILL INCLUDE AN INCREASE IN CLOUD COVER FROM  
AFOREMENTIONED ACTIVITY, WHICH WILL HOLD TEMPERATURES DOWN SLIGHTLY  
FROM SATURDAY. THE FRONT ENCOUNTERS A WARM, MOIST AIR MASS, BUT ONE  
THAT IS INITIALLY CAPPED SUNDAY MORNING AND INCLUDES WEAK  
FLOW/SHEAR. ONCE AIR BECOME UNCAPPED, SCATTERED SHOWERS AND  
THUNDERSTORMS REEMERGE DURING THE AFTERNOON AND EVENING.  
 
THE STALLED BOUNDARY REMAINS THE FOCUS FOR ADDITIONAL CHANCES IN THE  
EARLY PORTION OF THE WEEK WITH DIURNALLY DRIVEN THUNDERSTORMS THAT  
LACK ANY REAL ORGANIZATION AS A RESULT OF WEAK FLOW. THE BIGGEST  
QUESTION MAY CENTER ON TUESDAY AS SURFACE HIGH PRESSURE PASSES TO  
THE NORTHEAST BUT MAY HAVE ENOUGH INFLUENCE TO REDUCE THE POTENTIAL  
OVER EASTERN SECTIONS OF THE CWA. IT SEEMS THAT NBM GUIDANCE MAY BE  
PICKING UP ON THIS A LITTLE MORE AS THE BROAD SPREAD OF LOW POPS  
HAVE COME DOWN SOME AND THE RELATIVELY HIGHER POTENTIAL TO THE  
SOUTHWEST FORM A HORSESHOE AROUND THE INFLUENCE OF THE SURFACE RIDGE.  
I EXPECT THIS TO BE RESOLVED IN TIME TO PROVIDE BETTER DETAIL TO THE  
SPREAD AND MAGNITUDE OF POTENTIAL AS TUESDAY APPROACHES.  
 
AN ADDITIONAL CONSIDERATION WILL BE THE MEAN UPPER LEVEL FLOW AS  
RIDGING BUILDS WESTWARD AND STRENGTHENS OVER THE FOUR CORNERS REGION  
THROUGH MIDWEEK. QUASI-ZONAL UPPER LEVEL FLOW TRANSITIONS TO  
NORTHWEST FLOW OVER THE CENTRAL U.S., WHICH MAY BE CONDUCIVE FOR  
DRIVING SHORTWAVES AROUND THE NORTHERN PERIPHERY OF THE RIDGE AND  
INTO THE PLAINS/MISSISSIPPI VALLEY. THIS IS MORE LIKELY TO BE THE  
CASE BY MIDWEEK, WHILE EARLY WEEK POTENTIAL IS ATTRIBUTED TO THE  
STALLED SURFACE BOUNDARY. IF SO, THE BEST POTENTIAL FOR RAINFALL MAY  
ACTUALLY BE MID TO LATE WEEK.  
 
MAPLES  
 
 
   
AVIATION  
(FOR THE 12Z TAFS THROUGH 12Z SATURDAY MORNING)  
ISSUED AT 534 AM CDT FRI JUL 4 2025  
 
SKIES ARE MOSTLY CLEAR THIS MORNING WITH FEW HIGH CLOUDS STREAMING  
THROUGH THE REGION. CALM TO LIGHT AND VARIABLE SURFACE WINDS ARE  
EXPECTED TO INCREASE TO 5-10 KNOTS AND TURN OUT OF THE SOUTH FROM  
MID TO LATE MORNING. VFR CONDITIONS ARE EXPECTED THROUGH THE END O  
PERIOD.  
 
MAPLES  
 
 
   
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