433
FXUS63 KLSX 240336
AFDLSX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ST LOUIS MO
1036 PM CDT WED SEP 23 2026
KEY MESSAGES
- NORMAL TO BELOW NORMAL TEMPERATURES WILL REMAIN IN PLACE
THROUGH THE WEEKEND.
- THE NEXT CHANCE FOR WIDESPREAD RAIN ARRIVE NEXT WEEK.
SHORT TERM /THROUGH FRIDAY/
ISSUED AT 134 PM CDT WED SEP 23 2026
THERE IS A WEAK UPPER LEVEL LOW/SHORTWAVE OVER THE MIDWEST SITUATED
TO THE SOUTH OF A ANOMALOUSLY STRONG RIDGE OVER EASTERN CANADA.
THAT RIDGE IS REFLECTED IN THE SURFACE PATTERN BY A 1040 MB HIGH
CENTERED OVER SE CANADA AND NEW ENGLAND, RESULTING IN PERSISTENT,
COOL NORTHEASTERLY FLOW OVER THE MID-MISSISSIPPI VALLEY. THE NE
FLOW, COUPLED WITH AMPLE LOW LEVEL MOISTURE ASSOCIATED WITH THE
WEAK UPPER LOW MENTIONED ABOVE, HAS BEEN ADVECTING STRATUS WESTWARD
ACROSS THE FORECAST AREA, KEEPING TEMPERATURES BELOW NORMAL,
ESPECIALLY OVER OUR EASTERN COUNTIES. THE STRATUS WILL CONTINUE TO
MIX SOMEWHAT THIS AFTERNOON, BUT SHOULD BE REINFORCED BY CONTINUED
MOISTURE ADVECTION THROUGH TOMORROW MORNING. THIS WILL PUSH LOW
STRATUS BACK TO WEST,REACHING SOMEWHERE NEAR THE MISSISSIPPI RIVER.
THE PRECISE LOCATION OF THOSE CLOUDS WILL DICTATE TEMPERATURES
TONIGHT, WITH MOSTLY CLEAR AREAS DROPPING INTO THE LOW 50S OR MAYBE
EVEN UPPER 40S IN SHELTERED LOCATIONS.
THE ABOVE PATTERN WILL SLOWLY DRIFT EAST OVER THE NEXT FEW DAYS,
WITH THE UPPER LOW GIVING WAY TO RIDGING ACROSS THE CENTRAL CONUS.
TOMORROW MORNING'S STRATUS WILL AGAIN MIX OUT THROUGH THE DAY,
PERHAPS A BIT QUICKER THAN TODAY GIVEN THAT THE UPPER LOW WILL BE
FURTHER FROM THE AREA. SHOULD THAT OCCUR, TEMPERATURES TOMORROW ARE
EXPECTED TO BE A FEW DEGREES WARMER THAN WHAT WE'RE EXPERIENCING
TODAY. TEMPERATURES SHOULD FURTHER MODERATE ON FRIDAY BENEATH THE
UPPER LEVEL RIDGE, PUSHING BACK TOWARD NORMAL AREA-WIDE.
LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/
ISSUED AT 134 PM CDT WED SEP 23 2026
ON FRIDAY NIGHT AND SATURDAY, A BROAD SHORTWAVE WILL BRIEFLY IMPINGE
ON THE RIDGE, DRIVING VERY MODEST CYCLOGENESIS OVER THE NORTHERN
PLAINS. AS A RESULT, MUCH OF THE DETERMINISTIC GUIDANCE DEPICTS A
WEAK WARM FRONT EXTENDING TO THE SOUTHEAST OF THE SHORTWAVE AND INTO
THE MID-MISSISSIPPI VALLEY. THIS WILL SUPPORT WIDESPREAD CLOUD
COVERAGE ON SATURDAY AND PERHAPS SOME LIGHT PRECIPITATION CLOSER
TO THE SHORTWAVE. IN FACT, LREF PROBABILITIES OF AT LEAST 0.01"
OF QPF EXCEED 50% IN NORTHEASTERN MO AND WEST-CENTRAL IL ON
SATURDAY AFTERNOON. GIVEN THE WEAK FORCING, I DO NOT EXPECT ANY
OF THIS PRECIPITATION TO BE IMPACTFUL, BUT IT SHOULD HELP PULL
TEMPERATURES BACK DOWN A BIT.
RIDGING WILL TAKE HOLD AGAIN ON SUNDAY AND INTO MONDAY AHEAD OF A
SHARP SHORTWAVE THAT'S EXPECTED TO MOVE THROUGH THE CENTRAL CONUS
SOMETIME ON TUESDAY OR WEDNESDAY. THIS WILL BE OUR NEXT CHANCE FOR
WIDESPREAD PRECIPITATION ACROSS THE REGION, WITH LREF 24 HOUR
PROBABILITIES OF > 0.01" AROUND 100% AND > 0.25" OVER 50%.
AVIATION /06Z TAFS THROUGH 12Z FRIDAY/
ISSUED AT 1028 PM CDT WED SEP 23 2026
LOW CEILINGS CONTINUE TO BE THE PRIMARY CONCERN DURING THE 06Z
TAF PERIOD, WITH WIDESPREAD MVFR CATEGORIES EXPECTED OVERNIGHT
THROUGH TOMORROW MORNING, ESPECIALLY AT UIN/STL/SUS/CPS. CURRENT
OBSERVATIONS (03Z) SHOW THAT LOCAL CEILINGS REMAIN ABOVE VFR
LEVELS, BUT CLOUDS UPSTREAM TO THE EAST ARE LOWER, AND CEILINGS
ARE LIKELY TO DROP OVERNIGHT DUE TO DIURNAL PROCESSES. WHILE THE
EXACT TIMING OF THIS LOWERING IS SOMEWHAT UNCERTAIN, WE
CONTINUE TO EXPECT AT LEAST A FEW HOURS OF MVFR CEILINGS BETWEEN
LATE TONIGHT AND MID MORNING TOMORROW AT THOSE TERMINALS. BRIEF
CEILING REDUCTIONS ARE ALSO POSSIBLE AT COU/JEF, BUT CONFIDENCE
IS MUCH LOWER THAT THE WESTERN EDGE OF THE CLOUD SHIELD (AND
ESPECIALLY THE MVFR CEILINGS) WILL MAKE IT THIS FAR WEST.
CEILINGS ARE EXPECTED TO GRADUALLY LIFT AND MOVE OFF TO THE
NORTHEAST BETWEEN LATE MORNING AND EARLY AFTERNOON, LEAVING
BEHIND VFR CONDITIONS THE REMAINDER OF THE PERIOD.
BRC
LSX WATCHES/WARNINGS/ADVISORIES
MO...NONE.
IL...NONE.
SHORT TERM...BSH
LONG TERM...BSH
AVIATION...19
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