915
FXUS63 KLSX 112352
AFDLSX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ST LOUIS MO
652 PM CDT FRI SEP 11 2026
KEY MESSAGES
- THERE IS A CHANCE FOR SHOWERS AND THUNDERSTORMS ACROSS PARTS
OF CENTRAL AND NORTHEAST MISSOURI INTO WEST CENTRAL ILLINOIS
TONIGHT INTO SATURDAY. THE CHANCE FOR RAIN SPREADS SOUTHEAST
TO MOST AREAS ALONG AND NORTH OF I-44/I-70 ON SUNDAY.
- TEMPERATURES WILL REMAIN ABOVE NORMAL FOR MOST OF THE AREA
INTO NEXT WEEK WITH A CHANCE FOR RAIN CONTINUING, MAINLY
ACROSS NORTHERN MISSOURI INTO CENTRAL ILLINOIS.
SHORT TERM /THROUGH SATURDAY NIGHT/
ISSUED AT 253 PM CDT FRI SEP 11 2026
ISOLATED SHOWERS AND A THUNDERSTORM OR TWO WILL CONTINUE TO
AFFECT PARTS OF THE AREA THROUGH THE AFTERNOON INTO TONIGHT,
MAINLY ACROSS SOUTHEAST MISSOURI AND SOUTHWEST ILLINOIS. THE
SLOW-MOVING SHORT WAVE FORCING THIS CONVECTION WILL WEAKEN AS IT
DRIFTS EAST INTO THE OHIO AND TENNESSEE VALLIES OVER THE NEXT
24-36 HOURS, AND THE THREAT FOR PRECIPITATION ASSOCIATED WITH
THIS WAVE SHOULD COME TO AN END EARLY SATURDAY MORNING.
MEANWHILE, THE TAIL END OF ANOTHER WAVE WILL MOVE THROUGH THE
NORTHERN PLAINS INTO THE UPPER MIDWEST. THIS WILL PUSH A COLD
FRONT SOUTH THROUGH IOWA INTO NORTHERN MISSOURI BY MID- MORNING
SATURDAY. THE FRONT IS FORECAST TO BECOME MORE EAST-WEST
ORIENTED AND STALL SOMEWHERE OVER NORTHERN MISSOURI INTO CENTRAL
ILLINOIS AS THE UPPER LEVEL SHORT WAVE OUTRUNS THE SURFACE
FRONT SATURDAY AFTERNOON/EVENING. THERE IS LITTLE CONSENSUS
AMONG THE GUIDANCE MEMBERS ON PRECIPITATION CHANCES ASSOCIATED
WITH THIS FRONT. FORECAST SOUNDINGS LOOK PRETTY CAPPED WHICH
SHOULD LIMIT THE POTENTIAL FOR CONVECTION. GENERALLY USED A
BLEND OF SHORT-RANGE GUIDANCE FOR THIS FORECAST AND KEPT 20-30
POPS ACROSS NORTHEAST INTO CENTRAL MISSOURI AS WELL AS WEST
CENTRAL ILLINOIS IN THE VICINITY OF THE FRONT. THE SOUNDINGS ARE
ALSO FAIRLY DRY IN THE LOW LEVELS SO THERE SHOULD BE MORE
SUNSHINE ON SATURDAY THAN THERE IS TODAY. WEST- SOUTHWEST FLOW
AHEAD OF THE FRONT AND GOOD INSOLATION WILL THEREFORE PUSH
TEMPERATURES INTO THE UPPER 80S AND LOW 90S IN MOST LOCATIONS
SATURDAY AFTERNOON. THE FRONT DRIFTS A LITTLE FARTHER SOUTH
SATURDAY NIGHT AS ANOTHER SHORT WAVE DIPS INTO THE UPPER
MIDWEST, AND SOME ADDITIONAL CONVECTION IS POSSIBLE IN CENTRAL
AND NORTHEAST MISSOURI INTO WEST CENTRAL ILLINOIS BEFORE SUNRISE
SUNDAY AS A WEAK LOW LEVEL JET RIDES UP OVER THE FRONT, BUT
GUIDANCE IS STILL PRETTY WISHY-WASHY ON TIMING AND COVERAGE SO
HAVE CAPPED POPS AT 30 PERCENT.
LONG TERM /SUNDAY THROUGH FRIDAY/
ISSUED AT 253 PM CDT FRI SEP 11 2026
DETERMINISTIC GUIDANCE PUSHES THE COLD FRONT SOUTH OF I-70/I-64 BY
LATE SUNDAY NIGHT/EARLY MONDAY, BUT AN UPPER LEVEL SHORT WAVE RIDGE
BUILDS INTO THE MIDWEST BY 12Z MONDAY MORNING WHICH BRINGS THE FRONT
TO A FINAL STOP. THE MODELS PRINT OUT PRECIP ALONG THE FRONT SUNDAY
INTO SUNDAY NIGHT AS THE LOW LEVEL JET CONTINUES TO RIDE OVER THE
COOLER AIR AT THE SURFACE. THE PRECIP REINFORCES THE BOUNDARY IN
THE DETERMINISTIC GUIDANCE, BUT THE NEXT UPSTREAM SHORT WAVE
INCREASES SOUTHWEST FLOW OVER THE GREAT PLAINS AND PUSHES THE FRONT
BACK INTO IOWA AND NORTHERN ILLINOIS BY LATE MONDAY NIGHT. WHILE
TEMPERATURES WILL BE COOLER IN THE LOW TO MID 80S NORTH OF THE FRONT
ACROSS NORTHEAST MISSOURI INTO WEST CENTRAL ILLINOIS SUNDAY AND
MONDAY, MOST AREAS FARTHER SOUTH WILL LIKELY CONTINUE IN THE UPPER
80S TO AROUND 90. ENSEMBLE GUIDANCE DOES SHOW QUITE A BIT OF
VARIANCE IN TEMPERATURES WITH MAX TEMP IQRS IN EXCESS OF 5 DEGREES ON
SUNDAY AND AS MUCH AS 10-12 DEGREES ON MONDAY. WHILE TEMPERATURES
DO STEADY OUT TUESDAY AND WEDNESDAY IN THE UPPER 80S TO LOW 90S
ACROSS THE AREA WITH THE FRONT IN IOWA, MUCH UNCERTAINTY REMAINS FOR
THE LATTER HALF OF THE WEEK AS THE UPPER RIDGE BREAKS DOWN AND THE
FRONT DRIFTS BACK INTO MISSOURI AND CENTRAL/SOUTHERN ILLINOIS. THE
LREF TEMPERATURE IQRS INCREASE TO 15+ DEGREES FOR THURSDAY AND
FRIDAY AND PRECIPITATION CHANCES INCREASE AGAIN AS THE FRONT MOVES
INTO AND THROUGH THE FORECAST AREA.
AVIATION /00Z TAFS THROUGH 06Z SUNDAY/
ISSUED AT 649 PM CDT FRI SEP 11 2026
VFR CONDITIONS ARE EXPECTED TO PREVAIL THROUGH THE TAF PERIOD
WITH CALM TO LIGHT WINDS. THERE IS A CHANCE FOR SOME PATCHY FOG
FOR JEF, SUS, AND CPS, BUT THE PROBABILITY IS LOWER THAN
YESTERDAY. THIS IS PRIMARILY DUE TO CONDITIONS STARTING OFF
WARMER AND DRYER ALONG WITH SLIGHTLY STRONGER WINDS.
LSX WATCHES/WARNINGS/ADVISORIES
MO...NONE.
IL...NONE.
SHORT TERM...CARNEY
LONG TERM...CARNEY
AVIATION...ASEL/KIMBLE
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