624
FXUS63 KLSX 062310
AFDLSX
AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE SAINT LOUIS MO
610 PM CDT WED AUG 6 2025
KEY MESSAGES
- MOSTLY DRY CONDITIONS WILL CONTINUE THROUGH SATURDAY WITH ONLY A SLIGHT
CHANCE OF SHOWERS AND THUNDERSTORMS FORECAST TOMORROW
AFTERNOON.
- FRIDAY AND SATURDAY WILL BE THE HOTTEST DAYS OF THE WEEK.
WIDESPREAD HEAT INDEX VALUES OF 95 - 100 DEGREES ARE EXPECTED.
SHORT TERM
(THROUGH LATE THURSDAY NIGHT)
ISSUED AT 222 PM CDT WED AUG 6 2025
REMNANTS OF A ONCE SEVERE MCS CONTINUE TO DECAY OVER WESTERN
MISSOURI. THUNDERSTORMS HAVE FIRED UP ALONG ITS OUTFLOW BOUNDARY IN
CENTRAL MISSOURI THIS AFTERNOON. SO FAR, THESE THUNDERSTORMS HAVE
PRODUCED LIGHTNING AND BRIEF HEAVY RAIN. GIVEN THE OVERWHELMING LACK
OF SHEAR AND POOR MID-LEVEL LAPSE RATES, THIS, AS WELL AS GUSTY
WINDS, IS LIKELY ALL THEY WILL BE ABLE TO ACCOMPLISH BEFORE
DISSIPATING. THIS ACTIVITY WILL WANE WITH THE LOSS OF DAYTIME
HEATING.
ADDITIONAL DEVELOPMENT IS FORECAST TO DIVE SOUTH INTO ILLINOIS THIS
EVENING, CONTINUING THE CHANCE FOR SHOWERS AND THUNDERSTORMS ON THAT
SIDE OF THE MISSISSIPPI. WITH THE LOSS OF INSTABILITY OVERNIGHT,
CONVECTION WILL BE WANING AS IT MOVES THROUGH THE CWA.
HIGH RESOLUTION GUIDANCE IS CONSISTENT IN SHOWING AN MCS PASS
THROUGH NORTHERN IOWA TOMORROW MORNING, BUT VARIES REGARDING A
SOUTHERN PORTION THAT MAY MOVE INTO NORTHEAST MISSOURI DURING THE
SAME TIMEFRAME. IF THIS SOUTHERN MCS DOES TRACK INTO MISSOURI, RAIN
AND CLOUD COVER WOULD KEEP TEMPERATURES DAMPENED, LOWER THAN OUR
CURRENT FORECAST HIGHS OF ABOUT 90 DEGREES. ANY OUTFLOW THE SYSTEM
LAYS OUT COULD ACT AS A CATALYST FOR CONVECTIVE INITIATION THAT
AFTERNOON. CONVECTION THAT DEVELOPS WOULD LIKELY BE SHALLOW AND
ISOLATED GIVEN HIGH MIXING HEIGHTS OF AROUND 850 MB AND CAPPING JUST
ABOVE AT 750 MB. THAT'S IF THE MCS OCCURS AT ALL AND IF IT MANAGES
TO MAINTAIN ITSELF LONG ENOUGH TO MAKE IT INTO EASTERN MISSOURI.
JAJA
LONG TERM
(FRIDAY THROUGH NEXT WEDNESDAY)
ISSUED AT 222 PM CDT WED AUG 6 2025
INFLUENCE OF A MID-LEVEL RIDGE AND CONTINUED LOW-LEVEL WARM AIR
ADVECTION WILL SUPPORT GRADUALLY INCREASING TEMPERATURES THROUGH THE
END OF THE WEEK. NATURALLY GIVEN THE TREND, FRIDAY AND SATURDAY WILL
BE THE HOTTEST DAYS OF THE WEEK WITH WIDESPREAD LOW TO MID-90S
FORECAST EACH DAY. DEWPOINTS IN THE 70S WILL MAKE CONDITIONS FEEL
EVEN HOTTER AS HEAT INDEX VALUES HOVER AROUND THE CENTURY MARK FOR
SOME LOCATIONS EACH DAY. DESPITE 100 DEGREE HEAT INDEX VALUES IN THE
FORECAST, A HEAT ADVISORY WILL LIKELY NOT BE NECESSARY DUE TO 1)
LACK OF 105 DEGREE HEAT INDEX VALUES AND 2) SHORT DURATION OF 100
DEGREE VALUES. CLOUDS AND PRECIPITATION ARE FORECAST TO RETURN TO AT
LEAST THE NORTHERN CWA SUNDAY, PUTTING AN END TO THE NEAR CRITERIA
HEAT INDICES. EVEN IF THIS SYSTEM SLOWS DOWN AND WE EXPERIENCE
ANOTHER DAY OF HEAT, THAT WOULD ONLY BE DAY 3/4 OF THE CONSECUTIVE
DAYS NEEDED TO WARRANT A HEAT ADVISORY BASED ON LONGEVITY.
AS MENTIONED PREVIOUSLY, THE CHANCE OF SHOWERS AND THUNDERSTORMS
RETURNS SUNDAY AS THE MID-LEVEL RIDGE ERODES AND GIVES WAY TO
TROUGHING. A SURFACE COLD FRONT WILL ACCOMPANY THE TROUGH AS IT
SPINS OVER THE NORTHERN CONUS, BUT QUASI-ZONAL FLOW ON ITS SOUTHERN
PERIPHERY WILL ENSURE IT MOVES SLOWLY THROUGH THE MIDWEST. THIS
FRONT WILL LIKELY WAVER AS IT CRAWLS SOUTH AND ALLOW MULTIPLE
SHORTWAVES TO INTERACT WITH IT. IN TERMS OF SENSIBLE WEATHER, THIS
MEANS MULTIPLE ROUNDS OF SHOWERS AND THUNDERSTORMS ARE LIKELY IN THE
CARDS FOR US EARLY NEXT WEEK. EXACT DETAILS ARE STILL UNRESOLVED
GIVEN THE DIFFERENCES REGARDING TIMING AND SHORTWAVE
CHARACTERISTICS, AND THIS IS REFLECTED ONCE AGAIN WITH ENSEMBLE
GUIDANCE PAINTING OUR AREA WITH 20 - 50% POPS EACH PERIOD FROM
SUNDAY ON. DESPITE THE UNCERTAINTIES, WITH THIS SET-UP IN PLACE AND
WITH SOUTHERLY WINDS ADVECTING GULF MOISTURE INTO THE REGION DURING
THIS TIMEFRAME, WE'LL NEED TO KEEP AN EYE ON THE POTENTIAL FOR HEAVY
RAIN EARLY NEXT WEEK.
JAJA
AVIATION
(FOR THE 00Z TAFS THROUGH 00Z THURSDAY EVENING)
ISSUED AT 609 PM CDT WED AUG 6 2025
DRY AND VFR FLIGHT CONDITIONS WILL CONTINUE AT ALL TERMINALS
THROUGH THE TAF PERIOD UNDER LARGELY SOUTHERLY WINDS THAT WILL
BECOME LIGHT AND VARIABLE OVERNIGHT.
DELIA
LSX WATCHES/WARNINGS/ADVISORIES
MO...NONE.
IL...NONE.
WFO LSX
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