300
FXUS63 KLSX 240830
AFDLSX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ST LOUIS MO
330 AM CDT THU SEP 24 2026
KEY MESSAGES
- CLOUDY SKIES AND SEASONABLY COOL TEMPERATURES ARE EXPECTED FOR
THE NEXT COUPLE DAYS.
- RAIN CHANCES RETURN THIS WEEKEND, WITH MORE WIDESPREAD AND
SIGNIFICANT (0.50+ INCHES) RAIN LIKELY MID-WEEK.
SHORT TERM /THROUGH FRIDAY/
ISSUED AT 327 AM CDT THU SEP 24 2026
CURRENT MESOANALYSIS SHOWS THAT THERE IS A WEAK, MID/UPPER-LEVEL
LOW PRESSURE CENTER OVER THE OHIO VALLEY WITH ANOMALOUSLY STRONG
SURFACE RIDGING OVER EASTERN CANADA (>99TH CLIMATOLOGICAL
PERCENTILE). THIS SURFACE HIGH IS SUPPORTING THE CONTINUED
NORTHEASTERLY SURFACE FLOW WE HAVE BEEN EXPERIENCING. THIS
NORTHEASTERLY FLOW COMBINED WITH ABUNDANT LOW-LEVEL MOISTURE AND
LOW-LEVEL COLD AIR ADVECTION, IS CONTINUING TO SUPPORT LOW LEVEL
STRATUS CLOUDS OVER MUCH OF THE REASON. THESE CLOUDS PREVENTED
TEMPERATURES ACROSS MOST OF THE REGION FROM DROPPING TOO MUCH
OVERNIGHT, ONLY INTO THE LOW 60S. SOME CLEARING IS PRESENT IN
NORTHERN MO WHERE TEMPERATURES WERE ABLE TO DROP INTO THE 50S.
THE VAST MAJORITY OF THESE CLOUDS WILL REMAIN OVER NORTHERN AND
FAR EASTERN MO AND SOUTHWESTERN AND WEST-CENTRAL IL., CONTINUING
TO MODERATE SURFACE TEMPERATURES. THIS AFTERNOON, FOR REGIONS
UNDER THE HEAVY CLOUD COVER, HIGHS ARE EXPECTED TO ONLY REBOUND
INTO THE UPPER 60S AND LOW 70S, WHILE AREAS THAT EXPERIENCE
THINNER CLOUDS (AND POSSIBLY THE PERIODIC SUNSHINE), WILL WARM
UP INTO THE MID 70S.
THE NBM CONTINUES TO STRUGGLE TO HANDLE TEMPERATURES WHEN
WIDESPREAD CLOUD COVER IS EXPECTED. CURRENT NBM GUIDANCE
CONTINUES THE CLOUD COVER INTO FRIDAY AND HAS HIGH TEMPERATURES
ABOUT 5-10 DEGREES WARMER THAN THIS AFTERNOON. AS THE MID/UPPER
LEVEL LOW MOVES TO THE EAST BEING REPLACED BY RIDGING, IT COULD
ALLOW CLOUDS TODAY TO MIX OUT SOONER THAN THEY DID YESTERDAY. IF
THE CLOUDS MIX OUT QUICKER THAN EXPECTED TOMORROW, IT WOULD
ALLOW TEMPERATURES TO BE WARMER THAN TODAY (MID TO UPPER 70S),
BUT IF THE CLOUDS ARE ABLE TO REMAIN APPROXIMATELY THE SAME THEN
TOMORROW’S HIGH TEMPERATURES COULD BE SIMILAR TO TODAY.
LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/
ISSUED AT 327 AM CDT THU SEP 24 2026
A PATTERN CHANGE IS EXPECTED GOING INTO THE WEEKEND, WITH A
GRADUAL WARM UP. THE GFS AND EPS ENSEMBLES ARE SHOWING THAT A
MID/UPPER-LEVEL RIDGE IS EXPECTED TO BUILD OVER THE MIDWEST INTO
THE WEEKEND, PUSHING THE SURFACE HIGH AND MID/UPPER LEVEL LOW TO
THE EAST. THIS WOULD BRING SOUTHERLY FLOW BACK TO THE AREA,
POSSIBLY INCREASING TEMPERATURES OVER THE WEEKEND INTO EARLY
NEXT WEEK. THERE REMAINS UNCERTAINTY IN THE EXACT MAGNITUDE OF
THE WARM UP HOWEVER. NBM AND LREF INTERQUARTILE RANGES FOR
SATURDAY THROUGH WEDNESDAY ARE AROUND 5-6 DEGREES, SO GUIDANCE
IS UNSURE IF WE WILL REMAIN IN THE MID TO UPPER 70S OR HEAT UP
INTO THE MID 80S. THESE WIDE RANGES ARE DRIVEN BY A RETURN OF
RAIN CHANCES WHICH COULD COOL TEMPERATURES AS LOW AS THE MID 60S
(10% PERCENTILE). LONG-RANGE DETERMINISTIC MODELS ARE ALSO
HINTING OF A SHARP SHORTWAVE MOVING THROUGH THE CENTRAL CONUS
TUESDAY AND WEDNESDAY THAT COULD BRING A COLD FRONT INTO THE
REGION, BUT ENSEMBLES DURING THE SAME TIME ARE HAVING A
DIFFICULT TIME CAPTURING THE TIMING OF THE FRONT WITH
INTERQUARTILE RANGES AROUND 10 DEGREES BY THE MIDDLE OF NEXT
WEEK. AS A RESULT, TEMPERATURES COULD REMAIN IN THE MID TO UPPER
70S OR DROP BACK INTO THE 60S TO LOWER 70S.
WITH THE APPROACHING PATTERN CHANGE, OUR CHANCES OF RAIN
INCREASE AGAIN. FRIDAY INTO SUNDAY, DETERMINISTIC MODELS SHOW A
SHORTWAVE MOVING THROUGH THE CENTRAL GREAT PLAINS AND INTO THE
MIDWEST PROVIDING SUPPORT FOR A CHANCE OF RAIN FRIDAY NIGHT
THROUGH SATURDAY. THE LREF INDICATES A 60-90% CHANCE OF
MEASURABLE RAINFALL ACROSS CENTRAL AND NORTHEASTERN MO OVER THE
WEEKEND, BUT AMOUNTS ARE NOT EXPECTED TO BE SIGNIFICANT WITH
ONLY A 40-60% CHANCE OF 0.25 INCHES OF RAIN IN NORTHEASTERN MO.
THE POSSIBLE SHARP SHORTWAVE DURING THE MIDDLE OF THE WEEK ALSO
BRINGS THE GREATEST CHANCE OF WIDESPREAD RAIN THROUGH THE
FORECAST PERIOD. LREF GUIDANCE SHOWS A 70-90% CHANCE OF 0.01
INCHES OF RAIN ACROSS OUR ENTIRE AREA, AND 50-60% CHANCE OF
0.50+ INCHES OF RAIN.
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...ASEL/GOSSELIN
LONG TERM...ASEL/GOSSELIN
AVIATION...19
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