209
FXUS63 KLSX 262325
AFDLSX
AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE SAINT LOUIS MO
625 PM CDT SUN OCT 26 2025
KEY MESSAGES
- RAIN WILL CONTINUE THROUGH THE AFTERNOON AND NIGHT TONIGHT
ALONG AND SOUTH OF I-70, GRADUALLY ENDING FROM WEST TO EAST BY
LATE MONDAY MORNING.
- ANOTHER ROUND OF WIDESPREAD RAIN WILL ARRIVE TUESDAY INTO
WEDNESDAY, WITH FAIRLY HIGH (60-70%) CHANCES FOR 0.50" OR MORE
OF RAIN FOR MOST OF THE AREA.
- BRISK TEMPERATURES STICK AROUND THIS WEEK, WITH SOME OF THE
COOLEST AIR WE'VE SEEN THIS SEASON BY WEDNESDAY.
SHORT TERM
(THROUGH LATE MONDAY NIGHT)
ISSUED AT 120 PM CDT SUN OCT 26 2025
THE CLOSED UPPER-LEVEL LOW RESPONSIBLE FOR TODAY'S DAMP, GLOOMY
DAY IS MEANDERING OUT OF THE SOUTHERN PLAINS AT THIS HOUR THROUGH
THE OZARKS ON ITS SLOW MARCH EAST. MUCH MORE ABUNDANT LOW-LEVEL
MOISTURE IS BEING DRAWN NORTH BY THE SYSTEM, LEADING TO A FAIRLY
EXPANSIVE (ALBEIT LIGHT) STRATIFORM PRECIPITATION SHIELD ALONG AND
SOUTH OF THE I-70 CORRIDOR. EMBEDDED IN THIS SHIELD ARE POCKETS
OF LOCALLY- MODERATE RAIN, BUT ARE NOT CONVECTIVE IN NATURE AND
POSE NO THREAT FOR THUNDER. THAT STREAM OF MOISTURE WILL
EVENTUALLY MOVE EAST OF THE REGION THIS EVENING AND BE PINCHED OFF
BY THE CYCLONIC UPPER- LEVEL FLOW, LEADING TO A GRADUAL DECREASE
IN STRATIFORM COVERAGE. RAIN WILL END IN AN EQUALLY-GRADUAL WAY
FROM WEST TO EAST WITH THE UPPER-LEVEL WAVE MAKING ITS EXIT
OVERNIGHT INTO MONDAY MORNING. ABUNDANT CLOUD COVER WILL REMAIN IN
PLACE, KEEPING TEMPERATURES OVERNIGHT FROM COOLING TOO MUCH.
THAT CLOUD COVER, PARTICULARLY IN MISSOURI, WILL LINGER AMIDST THE
BROAD, NEBULOUS CYCLONIC FLOW ALOFT AND STUNT DIURNAL TEMPERATURE
TRENDS IN GENERAL THROUGH MONDAY. NBM PROBABILITIES OF WARMING ABOVE
65 DEGREES ARE FAIRLY LOW (5-10%) IN MUCH OF MISSOURI ON MONDAY AND
NOT MUCH HIGHER IN ILLINOIS (20-30%) WHERE SOME INTREPID BREAKS OF
SUN MAY OCCUR. RAIN CHANCES WERE REFINED A BIT TO START THE WORK
WEEK AS WELL TO REFLECT A DEFINITIVE BREAK IN PRECIPITATION BETWEEN
OUR DEPARTING WEATHER SYSTEM AND THE NEXT WAVE THAT ARRIVES
OVERNIGHT MONDAY INTO EARLY TUESDAY MORNING. GUIDANCE IS
CONSISTENTLY SHOWING A SLOWER EVOLUTION FOR THIS SYSTEM, HOLDING
RAIN OFF UNTIL MIDNIGHT TUESDAY AT THE EARLIEST. WHILE THERE MAY BE
A FEW SHOWERS THROUGH SUNRISE TUESDAY, FORCING IS WEAK AND DIFFUSE
SO MOST LIKELY (80%) WON'T SEE MUCH RAIN UNTIL AFTER THEN.
MRB
LONG TERM
(TUESDAY THROUGH NEXT SUNDAY)
ISSUED AT 120 PM CDT SUN OCT 26 2025
THE SLOWER TREND IN THE PRECIPITATION ONSET CAN BE ATTRIBUTED TO A
CLEAR CONVERGENCE OF THE GUIDANCE REGARDING THE UPPER-LEVEL WAVE
EVOLUTION. MOST NOW FAVOR A QUICKER DEEPENING OF THE WAVE, CLOSING
OFF OVER WESTERN MISSOURI AS OPPOSED TO SOUTHEAST MISSOURI AS SOME
SOLUTIONS DEPICTED 24-48 HOURS AGO. THE RESULTANT STRENGTHENING IN
THE SURFACE LOW WILL PROVIDE AMPLE FORCING AND LIFT TO BRING
WIDESPREAD RAIN TO THE REGION. THE BEST CHANCES ARRIVE TUESDAY
AFTERNOON THROUGH THE NIGHT, WHEN THE MAIN THRUST OF UPPER-LEVEL
SUPPORT DIVES THROUGH THE NORTHWEST FLOW ALOFT. SURFACE CYCLOGENESIS
IS FORECAST TO OCCUR FAIRLY RAPIDLY DURING THE NIGHT TUESDAY INTO
WEDNESDAY MORNING, STRENGTHENING GRADIENT WINDS AND FURTHER
SUPPORTING A WIDESPREAD SOAKING RAIN. THE CLOUD COVER, WIDESPREAD
RAIN, AND 850MB TEMPERATURES BELOW THE 25TH CLIMATOLOGICAL
PERCENTILE WILL WORK IN CONCERT TO KEEP TEMPERATURES IN THE 50S (85-
95%+ CHANCE) WEDNESDAY AREAWIDE. ALL OF THIS AMIDST A 15-20MPH WIND
WILL MAKE FOR A RAW, NASTY DAY IN THE MID-MISSISSIPPI VALLEY.
RAIN WILL GRADUALLY TAPER FROM WEST TO EAST WITH THE LOW DEPARTING,
THOUGH ITS SPEED IS STILL SOMEWHAT IN QUESTION. I WOULD LEAN ON
SLOWER DEPICTIONS HERE, ESPECIALLY GIVEN HOW WOUND UP AND CLOSED THE
UPPER-LEVEL LOW IS. WHEN ALL IS SAID AND DONE LATE WEDNESDAY NIGHT
INTO EARLY THURSDAY MORNING, A WIDESPREAD AND BENEFICIAL RAIN WILL
BE THE ONLY IMPACT OF NOTE. NBM PROBABILITIES OF AT LEAST 0.25" OF
RAIN ARE FAIRLY HIGH (70-80%) OVER MOST OF THE FORECAST AREA, WITH
THOSE VALUES REMAINING MODESTLY HIGH (60-70%) FOR THE 0.50"
THRESHOLD. GIVEN THE SLUGGISH NATURE OF THE SYSTEM AND THE MORE
IMPRESSIVE FORCING, I WOULDN'T BE TOO SURPRISED IF LOCALIZED AMOUNTS
UP TO 1.00" OCCUR WHERE RAIN PERSISTS. WITH NO INSTABILITY TO SPEAK
OF IN ANY AVAILABLE GUIDANCE, CONVECTIVE ELEMENTS WILL BE FEW AND
FAR BETWEEN AND THUNDERSTORM CHANCES WILL BE VERY LOW (LESS THAN
5%). TEMPERATURES THURSDAY WON'T BE MUCH WARMER BY THE THERMOMETER,
BUT WITH WEAKER WINDS IT WILL BE FAR MORE TOLERABLE THAN WEDNESDAY.
DRY AND SEASONABLY-COOL WEATHER WILL TAKE HOLD JUST IN TIME FOR
TRICK-OR-TREATING ON HALLOWEEN, WITH A WEAK SURFACE RIDGE IN PLACE
OVER MUCH OF THE REGION. THAT SAID, WE REMAIN IN A LONGWAVE
TROUGHING PATTERN THROUGH THE WEEKEND, AND SOME ENSEMBLE GUIDANCE
DEPICTS A CLOSED LOW BARRELING THROUGH THE REGION WITH RECKLESS
ABANDON OVER THE WEEKEND. WHETHER THAT OCCURS REMAINS TO BE SEEN,
BUT IMPACTS BEYOND ANOTHER THREAT FOR RAIN ARE VERY LOW (LESS THAN
5%) AT THIS POINT. LOOKING BEYOND THE FORECAST PERIOD INTO EARLY
NOVEMBER, STRONG SIGNALS CONTINUE TO EXIST IN LONG-RANGE GUIDANCE
AND THE CIPS EXTENDED ANALOGS FROM SAINT LOUIS UNIVERSITY THAT
MORE SEASONABLE TEMPERATURES AND DRY WEATHER ARE ON THE WAY.
MRB
AVIATION
(FOR THE 00Z TAFS THROUGH 00Z MONDAY EVENING)
ISSUED AT 621 PM CDT SUN OCT 26 2025
LOW LEVEL MOISTURE CONTINUES TO STREAM NORTHWARD IN ADVANCE OF LOW
PRESSURE MOVING ACROSS THE REGION FROM WEST TO EAST. THIS IS
EXPECTED TO GRADUALLY DISSIPATE OVER THE NEXT SEVERAL HOURS AS THE
MOISTURE FLOW WEAKENS AND THE LOW BEGINS TO PUSH EAST. LOWER
CEILINGS (MVFR TO IFR) HAVE DEVELOPED ACROSS CENTRAL AND SOUTHERN
MO AND HAVE BEGUN TO CREEP INTO THE ST LOUIS METRO AS WELL. EXPECT
THESE CEILINGS TO THICKEN AND LOWER OVERNIGHT, WITH SOME LOWER
VISIBILITY POSSIBLE AS WELL AS LOW LEVEL MOISTURE LINGERS. THE
LOWER CEILINGS LIKELY LAST THROUGH THE DAY TOMORROW, THOUGH LOWER
VISIBILITY IS LESS LIKELY AFTER SUNRISE. LOWER CEILINGS LIKELY
STAY FAR ENOUGH SOUTH TO AVOID THE QUINCY TERMINAL WITH VFR LIKELY
THERE.
KIMBLE
LSX WATCHES/WARNINGS/ADVISORIES
MO...NONE.
IL...NONE.
WFO LSX
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