062
FXUS63 KLSX 252323
AFDLSX
AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE SAINT LOUIS MO
623 PM CDT SAT OCT 25 2025
UPDATE
ISSUED AT 622 PM CDT SAT OCT 25 2025
NUDGED LOW TEMPERATURES UP A FEW DEGREES TONIGHT, INTO THE 50S, AS
EXTENSIVE MID LEVEL CLOUD COVER WILL BE A SOLID BLANKET TO KEEP
TEMPERATURES FROM FALLING MUCH. STL HAS ONLY HAD A 4 DEGREE
TEMPERATURE RANGE TODAY (HIGH 58 AND LOW 54). THIS MORNING'S LOWS
WERE ALMOST ENTIRELY IN THE 50S AND I EXPECT THAT TO BE THE CASE
AGAIN TONIGHT. THE ONLY EXCEPTION TO THIS WILL BE AREAS THAT
FINALLY START TO GET SOME RAIN. IN THOSE AREAS WHERE RAIN DOES
BEGIN TO MAKE IT TO THE GROUND IN MORE THAN JUST A FEW SPRINKLES,
EVAPORATIVE COOLING WILL BE ABLE TO PULL TEMPERATURES DOWN INTO
THE 40S.
OTHERWISE OUR SITUATION REMAINS THE SAME WITH WAVE AFTER WAVE OF
MID LEVEL MOISTURE BEING PUSHED NORTHWARD, BUT A CONTINUAL SUPPLY
OF LOW LEVEL DRY AIR HAS KEPT MOST OF THIS FROM REACHING THE
GROUND. THE RAIN IS FALLING OUT OF 10,000FT CLOUD DECKS, SO
THERE'S NEARLY 2 MILES WORTH OF DRY AIR FOR THOSE RAIN DROPS TO
FALL THROUGH BEFORE REACHING THE GROUND, AND THAT LOW LEVEL DRY
AIR IS BEING RESUPPLIED BY LOW LEVEL ENE WINDS. EVENTUALLY,
THOUGH, A BETTER PUSH OF MOISTURE ON SUNDAY WILL BREAK THIS
BALANCE IN FAVOR OF MORE RAIN REACHING THE GROUND IN THE SOUTHERN
HALF OF THE REGION, THOUGH NORTHERN AREAS ARE LIKELY TO REMAIN
JUST CLOUDY AND COOL.
KIMBLE
KEY MESSAGES
- MOSTLY DRY CONDITIONS WILL GIVE WAY TO INCREASED RAIN CHANCES
BY TOMORROW, MAINLY SOUTH OF I-70. AFTER A BRIEF BREAK TO START
THE WORK WEEK, RAIN CHANCES RETURN TUESDAY THROUGH WEDNESDAY.
- SEASONABLE TEMPERATURES REMAIN IN PLACE THROUGH NEXT WEEK, WITH
THE COOLEST CONDITIONS LIKELY (80% CHANCE) ON WEDNESDAY.
SHORT TERM
(THROUGH LATE SUNDAY NIGHT)
ISSUED AT 204 PM CDT SAT OCT 25 2025
A SLUGGISH UPPER-LEVEL TROUGH CENTERED OVER THE SOUTHERN PLAINS
IS HELPING STREAMING MOISTURE POLEWARD. THE BROAD DIFFLUENCE ON
THE WAVE'S LEADING EDGE IS FORCING ABUNDANT CLOUD COVER AND WEAK,
INTERMITTENT SHOWERS THROUGH THE MID-MISSISSIPPI VALLEY. DESPITE
SATURATION IN THE MID-LEVELS AND PRECIPITABLE WATER VALUES
BETWEEN THE 75TH AND 90TH CLIMATOLOGICAL PERCENTILES COINCIDENT
WITH MODEST ASCENT, MODEL SOUNDINGS CONTINUE TO SHOW A FAIRLY DRY
LAYER FROM ROUGHLY 800MB TO THE SURFACE. AS A RESULT, ONLY A FEW
INTREPID DROPS ARE MAKING IT TO THE GROUND (MOSTLY IN CENTRAL AND
SOUTHERN MISSOURI WHERE THE DRY AIR IS SHALLOWER). THIS DRY AIR
WILL KEEP RAINFALL LIMITED AND LIGHT THROUGH MOST OF THE NIGHT
TONIGHT, AND THE CLOUD COVER WILL HELP INSULATE ANY RADIATIONAL
COOLING TO KEEP LOWS SIMILAR TO THIS MORNING'S VALUES (MID 40S TO
LOW 50S).
THE UPPER-LEVEL WAVE WILL SLOWLY DRIFT THROUGH THE REGION OVERNIGHT
AND ARRIVE AROUND SUNRISE TOMORROW. THE TRACK OF THE SYNOPTIC
FEATURES DOES NOT BODE WELL FOR CONVECTION REACHING THE BI-STATE
REGION, FAVORING A LIGHT TO MODERATE STRATIFORM RAIN. NEARLY ALL
AVAILABLE HIGH-RESOLUTION GUIDANCE FEATURES VIRTUALLY NO INSTABILITY
AND RELEGATES ANY MOISTURE RETURN OF CONSEQUENCE ACROSS ARKANSAS.
THE RESULT ON THE SENSIBLE WEATHER FOR OUR REGION WILL BE A COOL DAY
WITH LIGHT TO MODERATE RAIN THROUGHOUT THE DAY SOUTH OF I-70. WHILE
NOT CONSTANT, I EXPECT LESS DRY TIME THAN TODAY DOWN THERE. A SHARP
GRADIENT BETWEEN THOSE WHO WILL SEE MORE THAN A FEW DROPS AND THOSE
WHO WILL EXPERIENCE MORE PERSISTENT RAIN WILL LIKELY EXIST SOMEWHERE
IN THE VICINITY OF THE MISSOURI RIVER. THOSE SOUTH OF THIS GRADIENT
WILL SEE UPWARDS OF 0.50 INCHES (60-70% CHANCE), WITH LOWER AMOUNTS
WITH NORTHWARD EXTENT. THIS RAIN WON'T BE COMING DOWN AT ANY
TREMENDOUS RATE, SO NO HAZARDOUS IMPACTS ARE EXPECTED. CLOUDS REMAIN
IN PLACE WITH NEBULOUS TROUGHING ALOFT PROVIDING THE NECESSARY
FORCING, WHICH WILL AGAIN KEEP OVERNIGHT LOWS INTO MONDAY MORNING
ABOUT THE SAME AS PREVIOUS NIGHTS.
MRB
LONG TERM
(MONDAY THROUGH NEXT SATURDAY)
ISSUED AT 204 PM CDT SAT OCT 25 2025
WHILE THE UPPER-LEVEL LOW CURRENTLY APPROACHING US WILL DEPART
SOMETIME MONDAY, PER NEARLY ALL GUIDANCE, WE WILL REMAIN IN SOME
DEGREE OF TROUGHING AND WHAT CAN ONLY BE DESCRIBED AS A MESSY
PATTERN ALOFT. FOR THAT REASON, LINGERING RAIN CHANCES CONTINUE
THROUGH MONDAY (THOUGH I SUSPECT THEY ARE TOO HIGH AND THAT THE
BEGINNING OF THE WORK WEEK WILL BE LARGELY DRY). THERE IS STILL
GENERAL AGREEMENT AMONG THE ENSEMBLE GUIDANCE ENVELOPE AND
DETERMINISTIC MODELS THAT ANOTHER POTENT CLOSED UPPER-LEVEL LOW WILL
DIVE SOUTH THROUGH THE PLAINS INTO THE MID-MISSISSIPPI VALLEY
SOMETIME TUESDAY INTO WEDNESDAY. THAT'S ABOUT ALL THEY AGREE ON,
WITH CONTINUED DIFFERENCES IN THE SYSTEM'S TRACK, SPEED, AND
EVOLUTION LITTERING THE ENSEMBLE OUTPUT. THE SYSTEM WILL TRANSLATE
FAIRLY QUICKLY ACROSS MISSOURI TO START, BUT AT SOME POINT THE UPPER-
LEVEL WAVE WILL TILT NEGATIVELY AND THE SURFACE LOW WILL QUICKLY
DEVELOP. WHERE THIS HAPPENS IS UNCLEAR, AND WILL HAVE IMPLICATIONS
ON THE TIMING AND AMOUNT OF RAIN.
THERE IS INCREASED CONFIDENCE THAT TUESDAY AFTERNOON AND EVENING
HAVE THE BEST CHANCES (CURRENTLY 80-90% DURING THAT TIME PER THE
NBM) FOR RAIN ACROSS THE REGION. RAINFALL AMOUNTS ARE VERY UNLIKELY
(10% CHANCE) TO EXCEED 1.00 INCHES ANYWHERE WITH THIS SYSTEM GIVEN
THE LIMITED MOISTURE AND FAIRLY QUICK EVOLUTION OF THE SYSTEM. THE
HIGHEST TOTALS (CLOSER TO 0.50 INCHES) ARE CURRENTLY FORECAST OVER
SOUTHWEST/SOUTH-CENTRAL ILLINOIS BY WEDNESDAY AFTERNOON DUE TO THAT
AREA'S PROXIMITY TO THE MORE DEVELOPED (AND POTENTIALLY OCCLUDED)
SURFACE LOW. BY WEDNESDAY, THERE'S SURPRISING AGREEMENT IN MOST
GUIDANCE THAT A REINFORCING SHORTWAVE AND IMPULSE OF COLDER AIR
ALOFT WILL SEND HIGH TEMPERATURES 5-10 DEGREES BELOW NORMAL. THOSE
BRISK TEMPERATURES, COMBINED WITH A 10-20MPH NORTHERLY WIND AND
RAIN, WILL MAKE FOR A PRETTY RAW DAY.
THE WOUND UP SURFACE LOW AND ATTENDANT CLOSED LOW ALOFT TAKE THEIR
LEAVE OF US THROUGH THE DAY ON THURSDAY, LEADING TO TEMPERATURES
RECOVERING VERY SLIGHTLY AND A GRADUAL SLACKENING OF THE WINDS. DRY
CONDITIONS ARE CURRENTLY FORECAST FROM HERE ON OUT, INCLUDING ON
HALLOWEEN, WITH TEMPERATURES REMAINING NEAR TO SLIGHTLY-BELOW THE
MID-60S WE EXPECT FOR LATE OCTOBER. HALLOWEEN NIGHT CURRENTLY LOOKS
DRY AREAWIDE WITH HIGH SURFACE PRESSURE LARGELY IN CONTROL, WITH
HIGHS IN THE UPPER 50S TO LOW 60S AND LOWS IN THE MID-30S TO LOW
40S. WHILE UNCERTAINTY IN THE UPPER-LEVEL PATTERN JUMPS CONSIDERABLY
BY NEXT WEEKEND, THE ENSEMBLE GUIDANCE TRENDS US WARMER AND DRIER
(WHICH IS BACKED UP BY THE CIPS EXTENDED ANALOGS FROM SAINT LOUIS
UNIVERSITY).
MRB
AVIATION
(FOR THE 00Z TAFS THROUGH 00Z SUNDAY EVENING)
ISSUED AT 622 PM CDT SAT OCT 25 2025
VFR CONDITIONS CONTINUE ON A STEADY ENE WIND ACROSS THE REGION.
ALTHOUGH REGIONAL RADAR SHOWS RAIN ATTEMPTING TO MOVE INTO THE
AREA, THIS IS FALLING OUT OF A 10,000FT CLOUD DECK AND DRY AIR
BELOW IT IS PREVENTING MOST OF IT FROM REACHING THE GROUND. THERE
WILL BE PERIODS OF SPRINKLES OR LIGHT RAIN REACHING CENTRAL MO AND
THE ST LOUIS METRO AT TIMES OVERNIGHT, BUT IT WON'T BE ENOUGH TO
LOWER VISIBILITY. A BETTER PUSH OF MOISTURE ON SUNDAY WILL
EVENTUALLY ALLOW MORE RAIN TO REACH THE GROUND IN THE ST LOUIS
METRO AND POTENTIALLY INTO CENTRAL MO, BUT AGAIN IT WILL BE
DIFFICULT FOR THIS TO CAUSE REDUCED VISIBILITY. SOME GUIDANCE
TRIES TO BRING LOWER CEILINGS WITH THE RAIN TOMORROW, BUT
CONFIDENCE IS LOW ON THIS. REGIONAL OBSERVATIONS SHOW HIGH CLOUD
BASES EXTENDING ALL THE WAY INTO CENTRAL ARKANSAS WHERE MORE RAIN
HAS FALLEN AND THERE'S LESS DRY AIR, SO WE REMAIN SKEPTICAL AT THE
MOMENT THAT LOWER CEILINGS WILL PUSH THIS FAR NORTHWARD IN A TOP
DOWN MOISTENING ENVIRONMENT. HOWEVER, TO INDICATE THE POTENTIAL WE
HAVE INCLUDED A SCT CLOUD DECK IN THE TAF TOMORROW AFTERNOON.
QUINCY LIKELY REMAINS DRY AND VFR THROUGH THE ENTIRE FORECAST AS
THE MOISTURE NEVER MAKES IT THAT FAR NORTH.
KIMBLE
LSX WATCHES/WARNINGS/ADVISORIES
MO...NONE.
IL...NONE.
WFO LSX
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page