338
FXUS63 KLSX 250524
AFDLSX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ST LOUIS MO
1224 AM CDT FRI SEP 25 2026
KEY MESSAGES
- SEASONABLY COOL TEMPERATURES ALONG WITH CLOUDY CONDITIONS ARE
EXPECTED TO CONTINUE INTO THE WEEKEND.
- THERE ARE 30-60% CHANCES FOR LIGHT RAIN FRIDAY INTO SUNDAY,
GENERALLY ACROSS CENTRAL/NORTHEAST MO AND WEST-CENTRAL IL.
MORE WIDESPREAD AND SIGNIFICANT (0.50+ INCHES) RAIN IS
EXPECTED NEXT WEEK.
SHORT TERM /THROUGH SATURDAY/
ISSUED AT 242 PM CDT THU SEP 24 2026
A MID/UPPER-LEVEL RIDGE IS POSITIONED ACROSS NEW ENGLAND WITH A
CLOSED MID-LEVEL LOW TRAVERSING THE SOUTHERN PERIPHERY OF THIS RIDGE
TO THE EAST INTO THE OHIO RIVER VALLEY. THE SURFACE REFLECTION OF
THIS RIDGE, AN ANOMALOUSLY STRONG 1035MB HIGH, IS CENTERED ACROSS
SOUTHERN ONTARIO BRINING CONTINUED LOW-LEVEL NORTHEASTERLY FLOW INTO
THE REGION. THE CONTINUED LOW-LEVEL CAA FROM THE SLOW MOVING SURFACE
HIGH HAS ALLOWED FOR PERSISTENT AND RATHER IMPRESSIVE LOW-LEVEL
CLOUDS FOR LATE SEPTEMBER. ADDITIONALLY, A NARROW MID-LEVEL RIDGE IS
WORKING ITS WAY EASTWARD INTO THE MISSISSIPPI RIVER VALLEY. THE
EFFECTS OF THIS FEATURE (SUBSIDENCE/SINKING AIR) IS APPARENT ON
VISIBLE SATELLITE IMAGERY, INDICATED BY THE WESTERN EXTENT OF THE
STRATUS DECK THAT IS THROUGH THE CENTER OF MO. FOR MOST OF OUR AREA
TODAY, THIS STRATUS HAS GREATLY REDUCED DAYTIME HEATING, WITH
CURRENT AFTERNOON TEMPERATURES ONLY 4-7 DEGREES WARMER THAN THIS
MORNING'S LOWS. MOST LOCATIONS, AS OF 19Z, ARE IN THE MID TO LOW
60S, ASIDE FROM PORTIONS OF IL WHERE TEMPERATURES ARE NEAR 70, A
RESULT OF THINNER STATUS. A SLOW SCATTERING/LIFTING OF THE STRATUS
IS STILL FORECAST, BUT WILL LIKELY NOT HAPPEN UNTIL NEAR SUNSET OR
AFTER, RESULTING IN TEMPERATURES THAT STAY IN THE MID/UPPER 60S
ACROSS THE AREA. LOCATIONS THAT REMAINS MOSTLY CLOUDY TONIGHT WILL
STAY WARMER WITH LOWS IN THE 60S, WHILE LIGHT WINDS WILL ALLOW AREAS
THAT CLEAR TO LOWER INTO THE 50S, THANKS TO EFFICIENT RADIATIONAL
COOLING.
A SIMILAR SITUATION IS CERTAINLY POSSIBLE FRIDAY, AS BOTH THE
LOCATIONS OF THE MID-LEVEL RIDGE LOCATION AND LOW-LEVEL
NORTHEASTERLY CAA REMAIN RELATIVELY UNCHANGED FROM TODAY. STRATUS
MAY NOT BE AS WIDESPREAD FRIDAY FOR SOME AREAS, WITH HIGHER
CONFIDENCE IN CLOUDIER CONDITIONS NORTH OF I-70. THERE WILL BE
SUBTLE PIECES OF SHORTWAVE ENERGY TRAVERSING THE NORTHERN PERIPHERY
OF THE RIDGE, WORKING TO CREATE MORE WIDESPREAD CLOUD COVER ALONG
WITH SCATTERED SHOWERS. AS A RESULT, THERE IS A 30-60% CHANCE FOR
SHOWERS ACROSS NORTHEAST MO/WEST-CENTRAL IL FRIDAY INTO SATURDAY.
THIS WILL BE A LIGHT RAIN WITH LREF PROBABILITIES FOR 6HR RAINFALL
GREATER THAN 0.25" LESS THAN 30% ACROSS THE AREA. AREAS THAT STAY
LOCKED UNDER LOW-LEVEL CLOUDS WILL ONCE AGAIN STRUGGLE TO WARM OUT OF
THE 60S WHILE LOCATIONS THAT GET MORE CLEARING WILL WARM UP INTO THE
70S FRIDAY AFTERNOON.
LONG TERM /SATURDAY NIGHT THROUGH THURSDAY/
ISSUED AT 242 PM CDT THU SEP 24 2026
MID-LEVEL PIECES OF ENERGY CONTINUE TO SWING AROUND THE
NORTHERN PERIPHERY OF A RIDGE CENTERED ACROSS TX, RESULTING IN
LOW CHANCES FOR SCATTERED RAIN SHOWERS CONTINUING INTO SATURDAY
AND POSSIBLY SUNDAY. AS WE PROGRESS FURTHER INTO THE WEEKEND,
SOME OF THE BETTER CHANCES (50%) MOVE SOUTH AND EAST REACHING
PORTIONS OF CENTRAL/EAST-CENTRAL MO. SIMILAR TO FRIDAY, MOSTLY
LIGHT RAIN SHOWERS ARE FORECAST AS THERE IS LESS THAN A 20%
CHANCE FOR THUNDERSTORMS. THE BETTER INSTABILITY (MUCAPE >1,000
J/KG) STAYS TO THE WEST ACROSS THE GREAT PLAINS THIS WEEKEND,
WITH LREF MEAN MUCAPE VALUES STAYING BELOW 200 J/KG ACROSS THE
ENTIRE AREA. BY TUESDAY, THE LARGE-SCALE PATTERN BEGINS TO SHIFT
AS A LONGWAVE TROUGH SWINGS INTO THE INTERMOUNTAIN WEST AND THE
SOUTHERN RIDGE INTO THE DEEP SOUTH. THIS PLACES OUR AREA IN
SOUTHERLY FLOW LEADING TO WARM/MOIST ADVECTION THAT WILL SUPPORT
INCREASING CHANCES FOR MORE WIDESPREAD SHOWERS ALONG WITH
THUNDERSTORMS. THE LREF ILLUSTRATES THIS POTENTIAL WELL AS
PROBABILITIES FOR PRECIPITATION >0.50" REACHES 50% FOR WESTERN
PORTIONS OF THE AREA, INDICATING THE INCREASING CHANCES FOR MORE
WIDESPREAD BENEFICIAL RAIN. WITH SOUTHERLY FLOW IN PLACE,
TEMPERATURES IQRS STEADILY INCREASE NEXT WEEK TO VALUES CENTERED
JUST ABOVE AVERAGE. HOWEVER, THESE IQR SPREADS INCREASE TO 10
DEGREES BY WEDNESDAY AND THURSDAY, SHOWING THE POTENTIAL FOR A
COLD FRONT BEHIND NEXT WEEKS SYSTEM. THIS REVEALS A RETURN TO
NEAR OR SLIGHTLY BELOW NORMAL TEMPERATURES ARE POSSIBLE BY THE
END OF NEXT WEEK.
AVIATION /06Z TAFS THROUGH 12Z SATURDAY/
ISSUED AT 1222 AM CDT FRI SEP 25 2026
LOW CEILINGS REMAIN THE MOST PRESSING CONCERN DURING THE 06Z TAF
PERIOD. WHILE CEILINGS LIFTED TO VFR LEVELS AT STL/UIN/SUS/CPS THIS
EVENING, A SHIELD OF MVFR LEVEL STRATUS CONTINUES TO LINGER AROUND
COU/JEF. SOME BRIEF CLEARING IS POSSIBLE AT THE START OF THE PERIOD
AT THESE TERMINALS AS WELL, BUT OVERNIGHT AND EARLY THIS MORNING
MVFR CEILINGS ARE EXPECTED TO MOVE BACK INTO LOCAL TERMINALS. SKIES
SHOULD GRADUALLY LIFT TO VFR LEVELS BY SOMETIME EARLY TOMORROW
AFTERNOON, BUT ONCE AGAIN LOW CLOUDS MAY LINGER INTO EVENING IN SOME
AREAS, AND CONFIDENCE IN THE TIMING IS RELATIVELY LOW.
OTHERWISE, PRECIPITATION CHANCES REMAIN LOW DURING THIS PERIOD, BUT
LIGHT SHOWERS ARE EXPECTED AT COU/JEF JUST BEYOND 06Z SATURDAY.
LSX WATCHES/WARNINGS/ADVISORIES
MO...NONE.
IL...NONE.
SHORT TERM...PEINE
LONG TERM...PEINE
AVIATION...19
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