294
FXUS63 KLSX 112325
AFDLSX
AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE SAINT LOUIS MO
625 PM CDT THU SEP 11 2025
KEY MESSAGES
-ABOVE NORMAL TEMPERATURES WILL CONTINUE INTO NEXT WEEK WITH THE
WARMEST TEMPERATURES EXPECTED ON SATURDAY.
-THERE IS A 15-20% CHANCE FOR AFTERNOON SHOWERS AND THUNDERSTORMS
SUNDAY-WEDNESDAY.
SHORT TERM
(THROUGH LATE FRIDAY NIGHT)
ISSUED AT 222 PM CDT THU SEP 11 2025
THE WARM UP CONTINUES UNDER A MID-LEVEL RIDGE THAT IS BUILDING INTO
THE CENTRAL PLAINS AS THE CENTER OF AN OMEGA BLOCK. TEMPERATURES ARE
AIDED BY MILD WARM AIR ADVECTION IN THE LOW-LEVELS AS SOUTHWESTERLY
FLOW BECOMES ESTABLISHED TODAY. THIS WILL PULL 850 MB TEMPERATURES
INTO THE UPPER TEENS BY FRIDAY AFTERNOON, AND COMBINED WITH
PLENTIFUL SUNSHINE, WILL RESULT IN HIGH TEMPERATURES ON FRIDAY IN
THE LOW 90S, A FEW DEGREES WARMER THAN TODAY.
DELIA
LONG TERM
(SATURDAY THROUGH NEXT THURSDAY)
ISSUED AT 222 PM CDT THU SEP 11 2025
THE MID-LEVEL RIDGE WILL SHIFT EASTWARD OVER THE END OF THE WORK
WEEK AND INTO THE WEEKEND, SITTING SQUARELY ON TOP OF THE MID-
MISSISSIPPI VALLEY BY SATURDAY. THE LOW LEVEL HIGH WILL ALSO BE
CENTERED OVER THE REGION, AND 850 MB TEMPERATURES WILL PEAK ON
SATURDAY NEAR THE 99TH PERCENTILE. SATURDAY WILL THEREFORE BE THE
WARMEST DAY OF THE PERIOD, WITH HIGH TEMPERATURES PUSHING THE MID TO
UPPER 90S. TEMPERATURES WILL COOL A FEW DEGREES SUNDAY WITH
INCREASING HIGH LEVEL CLOUDS THAT WILL BLOCK SOME INSOLATION, BUT
HIGHS WILL STILL PEAK ABOVE 90 DEGREES. THE MID-LEVEL RIDGE AND LOW-
LEVEL HIGH WILL SHIFT EASTWARD SLIGHTLY AS THE NEW WORK WEEK BEGINS,
AND THOUGH TEMPERATURES WON'T BE AS HOT AS SATURDAY, HIGHS WILL
REMAIN IN THE 90S THROUGH MUCH OF THE WORK WEEK. CONFIDENCE IN THIS
IS HIGH AS THE INTERQUARTILE SPREAD FOR HIGH TEMPERATURES MONDAY-
WEDNESDAY IS 5 DEGREES OR LESS. RELATIVE HUMIDITY WILL BE LOW ENOUGH
THAT HEAT INDEX VALUES WILL ONLY BE A DEGREE OR TWO HIGHER THAN THE
TEMPERATURE. BUT AFTER SEVERAL WEEKS OF BELOW NORMAL TEMPERATURES,
THESE HIGHS MAY PUT SENSITIVE GROUPS AT RISK FOR HEAT RELATED
ILLNESSES.
AS MENTIONED IN PREVIOUS FORECASTS, THERE REMAINS A LOW (15-20%)
CHANCE FOR SHOWERS AND THUNDERSTORMS EACH AFTERNOON SUNDAY-WEDNESDAY
AS THE MID-LEVEL RIDGE SHIFTS EAST, INSTABILITY GROWS, AND THE CAP
WEAKENS. I EXPECT THIS WILL BE SIMILAR TO MID AUGUST WHEN WE HAD
ISOLATED AFTERNOON SHOWERS AND A THUNDERSTORM OR TWO THAT CROPPED UP
AND THEN DIMINISHED WITH SUNSET. A LUCKY FEW WILL GET SOME RAIN, BUT
IT ISN'T EXPECTED TO BE ENOUGH TO RESULT IN SIGNIFICANT IMPROVEMENT
IN THE DRY CONDITIONS.
THE PATTERN BEGINS TO SHOW SOME SHIFTS MID-WEEK WITH THE MID-LEVEL
RIDGE TIPPING TO THE NORTHEAST AND AN INCOMING TROUGH OVER THE
NORTHERN PLAINS DEPICTED IN ALL ENSEMBLE GUIDANCE. THE EVOLUTION OF
THESE FEATURES IS STILL VERY UNCERTAIN AT THIS POINT, BUT RELIEF
FROM 90 DEGREE TEMPERATURES COULD BE COMING. THE INTERQUARTILE
SPREAD FOR HIGH TEMPERATURES WIDENS DURING THE SECOND HALF OF NEXT
WEEK, WHICH SPEAKS TO THE UNCERTAINTY IN THE EVOLUTION AND IMPACT OF
THE MID-LEVEL FEATURES. HOWEVER, THE 75TH PERCENTILE DOES DECREASE
INTO THE LOW 90S, INCREASING CONFIDENCE THAT WHILE IT MAY NOT BE
VERY MUCH, TEMPERATURES COULD START TO COOL BEYOND THE CURRENT
FORECAST PERIOD.
DELIA
AVIATION
(FOR THE 00Z TAFS THROUGH 00Z FRIDAY EVENING)
ISSUED AT 620 PM CDT THU SEP 11 2025
VFR FLIGHT CONDITIONS ARE EXPECTED TO PREVAIL ACROSS THE AREA
THROUGH FRIDAY AFTERNOON. THERE COULD BE SOME PATCHY FOG IN RIVER
VALLEYS AND OTHER LOW-LYING/SHELTERED AREAS AGAIN TONIGHT, BUT
IT'S NOT VERY LIKELY. LIGHT AND VARIABLE WINDS ARE EXPECTED TO
SETTLE DOWN TO A SOUTH OR SOUTHEASTERLY DIRECTION ON FRIDAY.
CARNEY
CLIMATE
ISSUED AT 218 PM CDT WED SEP 10 2025
RECORD DAILY HIGHS FRIDAY 9/12 THROUGH MONDAY 9/15:
9/12 | 9/13 | 9/14 | 9/15
STL 98 100 101 101
COU 100 99 104 101
UIN 99 100 99 100
DELIA
LSX WATCHES/WARNINGS/ADVISORIES
MO...NONE.
IL...NONE.
WFO LSX
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page