511
FXUS63 KLSX 060805
AFDLSX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAINT LOUIS MO
305 AM CDT WED AUG 6 2025
KEY MESSAGES
- TYPICAL SUMMER WARMTH AND HUMIDITY WILL PREVAIL INTO THE
WEEKEND.
- LARGELY DRY CONDITIONS ARE ALSO EXPECTED THROUGH SATURDAY, BUT
THERE IS A CONDITIONAL 20 PERCENT CHANCE OF SHOWERS AND
THUNDERSTORMS THIS AFTERNOON AND THURSDAY.
SHORT TERM
(THROUGH LATE THURSDAY AFTERNOON)
ISSUED AT 304 AM CDT WED AUG 6 2025
CALM WINDS AND RADIATIONAL COOLING ARE ALLOWING PATCHY FOG TO
DEVELOP THROUGH SUNRISE ACROSS POTIONS OF SOUTHWESTERN IL AND RIVER
VALLEYS ELSEWHERE, BUT IT IS POSSIBLE THAT SCATTERED MID-LEVEL
CLOUDS ASSOCIATED WITH A PASSING MID-LEVEL VORT MAX INTERRUPT THE
FOG AT TIMES.
OTHERWISE, THE MID-MISSISSIPPI RIVER VALLEY WILL REMAIN POSITIONED
BENEATH UPPER/MID-LEVEL NORTHWESTERLY FLOW AHEAD OF AN UPSTREAM
RIDGE. THERE HAS BEEN A SLIGHT INCREASE IN MODEL GUIDANCE HAVING
WEAKENING/DISSIPATING MCSS, ONE OF WHICH ONGOING IN THE NORTHERN
PLAINS EARLY THIS MORNING, APPROACH THE CWA FROM THE NORTHWEST AND
SOME SHOWERS AND THUNDERSTORMS SUBSEQUENTLY REDEVELOPING WITH
REMNANT MCVS PROVIDING FORCING AND WEAKENING CONVECTIVE INHIBITION.
AS A RESULT, HREF PROBABILITIES OF SHOWERS AND THUNDERSTORMS ARE 10
TO 20 PERCENT IN CENTRAL/NORTHEASTERN MO AND WEST-CENTRAL IL THIS
AFTERNOON AND SPORADICALLY ACROSS MORE OF THE CWA ON THURSDAY.
HOWEVER, THESE PROBABILITIES ARE ENTIRELY CONDITIONAL ON THE
SURVIVAL OF UPSTREAM MCSS/MCVS WITH PREDOMINANTLY DRY CONDITIONS
STILL MOST LIKELY SINCE THERE WILL BE NEBULOUS FORCING OTHERWISE.
THERE ARE SOME INGREDIENTS THAT SUGGEST THERE IS ALSO A NON-ZERO
CHANCE SEVERE THUNDERSTORMS AND HEAVY RAINFALL BUT CONFIDENCE IS
EVEN LOWER IN THOSE IMPACTS AT THIS POINT. PERSISTENT BUT WEAK LOW-
LEVEL SOUTHERLY TO SOUTHEASTERLY FLOW WILL ALSO RESULT IN A GRADUAL
WARMING AND MOISTENING TREND WITH STEADY WAA AND MOISTURE TRANSPORT.
THEREFORE, HIGH TEMPERATURES WILL WARM INTO THE MID-80S TO LOW-90S F
TODAY WITH 90S F BECOMING MORE COMMON ON THURSDAY. SHOWERS AND
THUNDERSTORMS AND AT LEAST CLOUDS DO DECREASE CONFIDENCE IN THE
TEMPERATURE FORECAST FOR THURSDAY, BUT NBM INTERQUARTILE RANGES ARE
STILL LESS THAN 5 F AND HOLD SOME CONFIDENCE IN THE FORECAST.
DEWPOINTS IN THE UPPER 60S TO LOW-70S F WILL KEEP HEAT INDEX VALUES
FROM BECOMING DANGEROUS.
PFAHLER
LONG TERM
(THURSDAY NIGHT THROUGH TUESDAY)
ISSUED AT 304 AM CDT WED AUG 6 2025
THERE IS EVEN LESS SUPPORT FOR ANY PRECIPITATION FRIDAY AND SATURDAY
WITH THE AXIS OF THE UPPER-LEVEL RIDGE FINALLY REACHING THE MID-
MISSISSIPPI RIVER VALLEY, SUPPRESSING OR DEFLECTING ADDITIONAL
MCSS/MCVS. FRIDAY AND SATURDAY ARE ALSO EXPECTED TO BE THE WARMEST
DAYS OF THE PERIOD ACROSS THE CWA WITH 850-HPA TEMPERATURES FLIRTING
WITH THE 90TH CLIMATOLOGICAL PERCENTILE, EQUATING TO WIDESPREAD HIGH
TEMPERATURES AROUND 90 TO THE MID-90S F. WITH DEWPOINTS GENERALLY IN
THE LOW-70S, AFTERNOON HEAT INDEX VALUES COULD STRADDLE 100 F;
HOWEVER, THE LONGEVITY OF THESE VALUES ARE UNCERTAIN AS THE PATTERN
BEGINS TO CHANGE INTO NEXT WEEK WITH CONFIDENCE LOW THAT
CONVENTIONAL DANGEROUS LONGEVITY THRESHOLDS WILL BE REACHED.
SUNDAY INTO NEXT WEEK, THE UPPER-LEVEL RIDGE IS PROGGED TO BREAK
DOWN AS A TROUGH TRACKS ACROSS THE NORTHERN-TIER OF THE CONUS,
CONTRIBUTING TO SOME VARIATION OF QUASI-ZONAL FLOW OVER THE MID-
MISSISSIPPI RIVER VALLEY WITH A POTENTIALLY WETTER AND MORE ACTIVE
PATTERN ACROSS THE REGION. THE DETAILS OF THIS PATTERN ARE NOT CLEAR
DUE TO VARIABILITY ACROSS MODEL GUIDANCE IN THE TIMING/NATURE OF
PASSING SHORTWAVE TROUGHS OR MCVS ALONG WITH THE ARRIVAL AND
SOUTHWARD PROGRESSION OF A COLD FRONT, RESULTING IN BROAD-BRUSHED 20
TO 50 PERCENT PROBABILITIES OF SHOWERS AND THUNDERSTORMS IN ENSEMBLE
MODEL GUIDANCE FROM SUNDAY MORNING ONWARD. THESE PROBABILITIES ARE
HIGHEST INITIALLY ACROSS NORTHEASTERN MO AND WEST-CENTRAL IL SUNDAY
INTO MONDAY BEFORE SHIFTING ACROSS A LARGER PORTION OF THE CWA ON
TUESDAY, A REFLECTION OF THE UNDERLYING SOUTHWARD PROGRESSION OF THE
COLD FRONT. NBM TEMPERATURE DISTRIBUTIONS STILL INCREASE INTO EARLY
NEXT WEEK, BUT THERE HAS BEEN A SLIGHT CLUSTERING OF MEMBERSHIP
TOWARD HIGH TEMPERATURES ONLY MARGINALLY COOLING AFTER SATURDAY WITH
INCREASING BACKING OF A SLOWER FRONTAL PROGRESSION INTO THE CWA.
PFAHLER
AVIATION
(FOR THE 06Z TAFS THROUGH 06Z WEDNESDAY NIGHT)
ISSUED AT 1104 PM CDT TUE AUG 5 2025
VFR FLIGHT CONDITIONS ARE EXPECTED TO PREVAIL THROUGH WEDNESDAY.
FOG IS POSSIBLE BEFORE SUNRISE WEDNESDAY MORNING, PRIMARILY IN
RIVER VALLEYS AND OTHER SHELTERED SPOTS. ANY FOG THAT DEVELOPS
SHOULD LIFT AND DISSIPATE QUICKLY AFTER SUNRISE.
CARNEY
LSX WATCHES/WARNINGS/ADVISORIES
MO...NONE.
IL...NONE.
WFO LSX
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page