335
FXUS63 KLSX 100945
AFDLSX
AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE SAINT LOUIS MO
445 AM CDT WED SEP 10 2025
KEY MESSAGES
- WELL-ABOVE AVERAGE TEMPERATURES AND LARGELY DRY CONDITIONS WILL
PERSIST THROUGH THE WEEKEND, WITH INCREASING CONFIDENCE IN
CONTINUATION INTO EARLY NEXT WEEK.
SHORT TERM
(THROUGH LATE THURSDAY AFTERNOON)
ISSUED AT 243 AM CDT WED SEP 10 2025
UPPER-LEVEL FLOW HAS BECOME NORTHWESTERLY OVER THE MID-MISSISSIPPI
RIVER VALLEY, WHICH WILL PERSIST THROUGH THURSDAY. WEAK MID-LEVEL
SHORTWAVE TROUGHS/PERTURBATIONS IN THIS FLOW WILL PRODUCE WAVES OF
UPPER/MID-LEVEL CLOUDS AS TIMES AND POSSIBLY SOME SPRINKLES,
ESPECIALLY THIS MORNING ACROSS CENTRAL/SOUTHEASTERN MO IN THE
NORTHEASTERN BRANCH OF A WEAK LLJ. HOWEVER, HREF PROBABILITIES OF
ANY MEASURABLE RAINFALL THROUGH THURSDAY ARE LESS THAN 10 PERCENT,
OWING TO OVERALL WEAK FORCING AND MODEST LOW-LEVEL MOISTURE.
OTHERWISE, WEAK LOW-LEVEL SOUTHERLY FLOW AND WAA WILL RESULT IN A
WARMING TREND WITH HIGH TEMPERATURES TODAY REACHING THE MID-80S TO
NEAR 90 F. ALTHOUGH THERE WILL LIKELY BE A LAPSE IN WAA ON THURSDAY
AS LOW-LEVEL FLOW BRIEFLY BECOMES VERY WEAK, GREATER INSOLATION WILL
ACT TO MAINTAIN THE WARMING TREND WITH HIGH TEMPERATURES ANOTHER
COUPLE DEGREES F WARMER.
PFAHLER
LONG TERM
(THURSDAY NIGHT THROUGH TUESDAY)
ISSUED AT 243 AM CDT WED SEP 10 2025
LATE THURSDAY INTO FRIDAY, AN UPPER-LEVEL RIDGE IS EXPECTED TO
AMPLIFY INTO THE MID-MISSISSIPPI RIVER VALLEY AS THE FLOW PATTERN
ACROSS THE CONUS BECOMES CONFIGURED INTO AN OMEGA BLOCK-LIKE PATTERN
THAT PERSISTS AT LEAST THROUGH THE WEEKEND. PERSISTENT LOW-LEVEL
SOUTHWESTERLY FLOW/WAA WITH 850-HPA TEMPERATURES REACHING THE 90TH
CLIMATOLOGICAL PERCENTILE AND RADIATIVE PROPERTIES OF DRY
GROUND/VEGETATION WILL BE FAVORABLE FOR WIDESPREAD HIGH TEMPERATURES
AROUND 90 TO THE MID-90S F. A FEW READINGS IN THE UPPER 90S F CANNOT
BE RULED OUT ON SATURDAY AND SUNDAY WHEN 850-HPA TEMPERATURES PEAK
DEPENDING ON CLOUD COVER. THAT BEING SAID, MOISTURE WILL LIKELY
STILL REMAIN LIMITED ENOUGH TO KEEP HEAT INDEX VALUES FROM RISING
MUCH ABOVE AIR TEMPERATURES. MODEST INSTABILITY AND WEAK CONVECTIVE
INHIBITION ALSO LEADS TO SOME CONCERN FOR DIURNAL SHOWERS OR
THUNDERSTORMS AS EARLY AS FRIDAY, SUGGESTED BY 10 TO 20 PERCENT OF
ENSEMBLE MODEL MEMBERSHIP. HOWEVER, NEBULOUS FORCING AND LOW
CONFIDENCE IN COVERAGE AND LOCATION KEEPS POPS MAINLY BELOW
MENTIONABLE LEVELS AT THIS POINT.
GLOBAL MODEL GUIDANCE ARE IN LOOSE AGREEMENT THAT THERE WILL BE SOME
REPOSITIONING AND/OR WEAKENING OF THE UPPER-LEVEL RIDGE AND THE
BLOCKING PATTERN AS A WHOLE NEXT WEEK. HOW THIS PROCESS TRANSPIRES
STILL VARIES, BUT THERE IS LESS AND LESS ENSEMBLE MODEL MEMBERSHIP
THAT HAVE AN UPPER-LEVEL TROUGH OVER THE GREAT LAKES CLOSE ENOUGH TO
FORCE A COLD FRONT FULLY INTO THE MID-MISSISSIPPI RIVER VALLEY,
WHICH IS REFLECTED BY DECREASING PROBABILITIES OF MEASURABLE
RAINFALL AND A SHIFT IN NBM TEMPERATURES TOWARD THE WARMER END OF
THE ENVELOPE. THAT BEING SAID, THERE IS STILL A MORE GRADUAL COOLING
TREND IN THE NBM TEMPERATURE DISTRIBUTION EARLY NEXT WEEK AND AT
LEAST A THREAT OF DIURNAL SHOWERS AND THUNDERSTORMS WOULD CONTINUE.
HOWEVER, THERE IS LITTLE TO NO SUPPORT OF ANY WIDESPREAD RAINFALL
THROUGH EARLY NEXT WEEK.
PFAHLER
AVIATION
(FOR THE 12Z TAFS THROUGH 12Z THURSDAY MORNING)
ISSUED AT 445 AM CDT WED SEP 10 2025
PREDOMINANTLY DRY AND VFR FLIGHT CONDITIONS WILL PERSIST THIS TAF
PERIOD. A FEW SPRINKLES CANNOT BE RULED OUT THROUGH THURSDAY
MORNING, BUT NO IMPACTS ARE ANTICIPATED. WINDS WILL BE LIGHT AND
MOSTLY VARIABLE.
PFAHLER
LSX WATCHES/WARNINGS/ADVISORIES
MO...NONE.
IL...NONE.
WFO LSX
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