015
FXUS63 KLSX 051713
AFDLSX
AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE SAINT LOUIS MO
1213 PM CDT TUE AUG 5 2025
KEY MESSAGES
- ASIDE FROM ISOLATED AFTERNOON SHOWERS AND THUNDERSTORMS TODAY,
LARGELY DRY CONDITIONS WILL PERSIST THROUGH THE REST OF THE WEEK
AS TYPICALLY SUMMER WARMTH AND HUMIDITY GRADUALLY RETURN.
SHORT TERM
(THROUGH LATE WEDNESDAY AFTERNOON)
ISSUED AT 247 AM CDT TUE AUG 5 2025
WESTWARD-EXPANDING BL MOISTURE AND RADIATIONAL COOLING HAVE RESULTED
IN A COMBINATION OF STRATUS AND FOG ACROSS PORTIONS OF THE CWA EARLY
THIS MORNING. THROUGH SUNRISE, AREAS OF FOG ARE MOST FAVORED ACROSS
PORTIONS OF NORTHEASTERN, CENTRAL, AND SOUTHEASTERN MO WHERE THE
NOCTURNAL INVERSION WILL BE MOST SHALLOW. HOWEVER, THIS INVERSION IS
A LITTLE HIGHER (EVIDENT IN LATEST KSTL ACARS SOUNDINGS) ALONG/EAST
OF THE MISSISSIPPI RIVER, FAVORING MORE STRATUS THAN FOG IN THOSE
AREAS. ONCE DAYTIME HEATING COMMENCES, STRATUS/FOG WILL LIFT, BECOME
MORE CUMULIFORM, AND SCATTER THROUGH MORNING INTO AFTERNOON. MID-
LEVEL HEIGHTS WILL ALSO BE RISING TODAY BEHIND A DEPARTING UPPER-
LEVEL TROUGH, BUT AROUND 20 PERCENT OF HREF MEMBERSHIP DEPICT
ISOLATED AFTERNOON SHOWERS AND THUNDERSTORMS WITH DIURNAL
INSTABILITY WHERE CONVECTIVE INHIBITION WILL BE LOWEST. WITH
INCREASING INSOLATION THROUGH THE DAY AND LITTLE AIRMASS CHANGE FROM
YESTERDAY (ASIDE FROM MOISTENING) AND A SLIGHTLY WARMER START, HIGH
TEMPERATURES WILL, TOO, BE SLIGHTLY WARMER AND FIRMLY IN THE 80S F.
A SUBTLE MID-LEVEL VORT MAX COULD PROVIDE SOME UPPER/MID-LEVEL
CLOUDS TONIGHT, BUT WHERE RADIATIONAL COOLING TAKES PLACE MUCH OF
THE NIGHT, PATCHY FOG IS FORECAST TO DEVELOP ONCE AGAIN, MAINLY IN
RIVER VALLEYS.
PFAHLER
LONG TERM
(WEDNESDAY NIGHT THROUGH MONDAY)
ISSUED AT 247 AM CDT TUE AUG 5 2025
THE NORTHEASTERN BRANCH OF AN UPPER-LEVEL RIDGE CENTERED ACROSS THE
FOUR CORNERS REGION AND SOUTHERN PLAINS WILL DOMINATE THE MID-
MISSISSIPPI RIVER VALLEY WEDNESDAY INTO SATURDAY. ALTHOUGH MID-LEVEL
PERTURBATIONS/MCVS WILL NAVIGATE THE RIDGE, AROUND 90 PERCENT OF
ENSEMBLE MODEL MEMBERSHIP KEEPS THE CWA DRY, WITH THESE FEATURES
EITHER PASSING TO THE NORTH AND/OR DISSIPATING UPON ARRIVAL. AT LOW
LEVELS, SOUTHERLY TO SOUTHEASTERLY FLOW WILL ALLOW FOR A CONTINUED
GRADUAL WARMING AND MOISTENING (RISING DEWPOINTS) TREND THROUGH THE
WEEK WITH VERY WEAK BUT PERSISTENT WAA AND MOISTURE TRANSPORT
SOURCED FROM THE SOUTHEAST. NBM HIGH TEMPERATURE DISTRIBUTIONS ARE
TIGHTLY CLUSTERED AROUND THE MID-80S TO LOW-90S F WEDNESDAY AND
THURSDAY, WITH MORE WIDESPREAD 90S F BY FRIDAY ACCOMPANIED BY
DEWPOINTS RISING INTO THE 70S F ACROSS MOST OF THE CWA. HOWEVER,
RESULTING AFTERNOON HEAT INDEX VALUES ARE EXPECTED TO FALL JUST
SHORT OF DANGEROUS MAGNITUDE AND DURATION.
SUNDAY INTO EARLY NEXT WEEK, MODEL GUIDANCE REMAINS CONSISTENT ON
THE AFOREMENTIONED RIDGE BREAKING DOWN AS AN UPPER-LEVEL TROUGH
DEEPENS OVER THE NORTHERN-TIER OF THE CONUS, ULTIMATELY LEADING TO A
POTENTIALLY WETTER AND MORE ACTIVE PATTERN ACROSS THE MID-
MISSISSIPPI RIVER VALLEY. THE DETAILS OF THIS PATTERN ARE UNCERTAIN,
INCLUDING HOW QUICKLY A COLD FRONT REACHES THE REGION AND HOW LONG
IT REMAINS IN THE VICINITY AS IT EITHER WAVERS OR JUST HAS A VERY
SLOW SOUTHWARD PROGRESSION. MUCH OF THIS UNCERTAINTY STEMS FROM
DIFFERENCES IN THE AMPLITUDE AND PROGRESSION OF THE UPPER-LEVEL
TROUGH ALONG WITH THE CHARACTERISTICS OF MULTIPLE PASSING SHORTWAVE
TROUGHS/PERTURBATIONS NAVIGATING THE BASE OF THE TROUGH.
ACCORDINGLY, ENSEMBLE MODEL GUIDANCE HAS BROAD-BRUSHED 20 TO 50
PERCENT PROBABILITIES OF MEASURABLE RAIN FROM SUNDAY ONWARD ALONG
WITH NBM HIGH TEMPERATURE INTERQUARTILE RANGES INCREASING TO 5 TO 8
F. MORE SPECIFICALLY, THE 75TH PERCENTILE REMAINS STEADY IN THE 90S
F AND THE 25TH PERCENTILE COOLS INTO THE 80S IN ASSOCIATION WITH A
MORE PROGRESSIVE FRONT AND/OR WIDESPREAD CLOUDS AND PRECIPITATION.
PFAHLER
AVIATION
(FOR THE 18Z TAFS THROUGH 18Z WEDNESDAY AFTERNOON)
ISSUED AT 1210 PM CDT TUE AUG 5 2025
PESKY STRATUS CONTINUES TO SCATTER AND LIFT THIS MORNING WITH
WIDESPREAD VFR CONDITIONS EXPECTED THIS AFTERNOON. TONIGHT, PATCHY
FOG IS EXPECTED PRIMARILY IN RIVER VALLEYS. OTHERWISE, LIGHT AND
VARIABLE WINDS CONTINUE THROUGH THE PERIOD.
JAJA
LSX WATCHES/WARNINGS/ADVISORIES
MO...NONE.
IL...NONE.
WFO LSX
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