671   
FXUS63 KLSX 311954  
AFDLSX  
  
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE SAINT LOUIS MO  
254 PM CDT FRI OCT 31 2025  
   
KEY MESSAGES  
  
- A COLD FRONT WILL BRING A COOLER THAN NORMAL AIRMASS TO THE  
  REGION THIS WEEKEND WITH HIGH TEMPERATURES (40S/50S) 5-8   
  DEGREES BELOW NORMAL. TEMPERATURES GRADUALLY WARM NEAR TO ABOVE   
  NORMAL NEXT WEEK.  
  
- THERE IS A SLIGHT CHANCE (15-30%) OF SHOWERS OVER MOST OF THE  
  AREA SATURDAY. CHANCES INCREASE TO NEAR 60% OVER FAR SOUTHEAST  
  MISSOURI. RAINFALL AMOUNTS WILL BE LIGHT (TRACE TO 0.10").  
  
  
   
SHORT TERM  
  (THROUGH LATE SATURDAY NIGHT)  
ISSUED AT 245 PM CDT FRI OCT 31 2025  
  
(ANALYSIS/OVERVIEW)  
  
A LONGWAVE UPPER TROUGH HAS CONSUMED MUCH OF THE CONUS WITH MID-  
LEVEL RIDGING OVER THE WESTERN U.S. THE TROUGH INDUCES MULTIPLE   
DISTURBANCES THAT ROTATE THROUGH THE BROADER CYCLONIC FLOW, KEEPING   
AN ACTIVE UPPER LEVEL PATTERN OVER THE UPPER MIDWEST. SURFACE HIGH   
PRESSURE OVER THE EASTERN PLAINS HAS EXHIBITED ENOUGH INFLUENCE OVER   
THE MID-MISSISSIPPI VALLEY TO MAINTAIN MOSTLY CLEAR SKIES AHEAD OF A   
COLD FRONT. CLOUDS INCREASE NEAR THE FRONT, WHICH EXTENDS EAST TO   
WEST FROM NORTHERN ILLINOIS INTO IOWA. THE FRONT IS JUST BEGINNING   
TO ENCROACH ON THE NORTHERN SECTIONS OF MISSOURI AND WEST-CENTRAL   
ILLINOIS AS OF 19Z THIS AFTERNOON. SURFACE OBSERVATION SHOW NEAR   
NORMAL TEMPERATURES (60S) SOUTH OF THE FRONT AND MUCH COOLER   
(40S/50S), BELOW NORMAL TEMPERATURES NORTH OF THE BOUNDARY. COOLER   
TEMPERATURES ARE ACCOMPANIED BY DRIER AIR WITH DEWPOINTS IN THE .  
  
(THIS EVENING THROUGH 15Z SATURDAY)  
  
THE COLD FRONT OVER IOWA WILL MOVE SOUTHWARD THROUGH THE CWA   
OVERNIGHT AND INTO SOUTHERN SECTIONS OF MISSOURI AND ILLINOIS BY   
SATURDAY MORNING. RELATIVELY HIGHER MOISTURE ASSOCIATED WITH   
ANOTHER, WEAKER SHORTWAVE OVER COLORADO, WILL BE PULLED EASTWARD   
WITHIN UPPER LEVEL WESTERLIES SOUTH OF THE UPPER LOW. CLOUDS WILL   
CONTINUE TO INCREASE FROM WEST TO EAST AHEAD OF THE FRONT BEFORE   
BEING SHUNTED INTO THE SOUTHERN SECTIONS OF THE CWA SATURDAY   
MORNING. THE FRONT IS MOVING THROUGH DURING DIURNAL MINS IN ADDITION   
TO HIGH-BASED (ALOFT OF 600MB) SATURATION OVER DRY AIR BELOW 850MB.   
A STRAY SHOWER CANNOT BE ENTIRELY RULED OUT, BUT DRY CONDITIONS ARE   
HEAVILY FAVORED WITH HREF PROBABILITIES SHOWING 10% OF THE MEMBERS   
DOTTING THE FRONT RAINFALL POTENTIAL. GUSTY WINDS RUN ALONG AND JUST   
BEHIND THE FRONT, BUT THIS LOOKS BRIEF (1-2 HOURS) CONSIDERING THE   
COMPACT NATURE OF THE LLJ SPEED MAX FOLLOWING THE FRONT.  
  
ANOTHER ITEMS NOTE WITH THE FRONT TONIGHT IS THE POTENTIAL FOR LOW   
TEMPERATURES NEAR OR SLIGHTLY BELOW FREEZING SATURDAY MORNING. THIS   
COMES IN A NARROW CORRIDOR OF DRY AIR THAT SEPARATES THE MOISTURE   
POOL OVER THE PLAIN/MID-MISSISSIPPI VALLEY FROM THE POOL OF MOISTURE   
ASSOCIATED WITH THE UPPER LOW TO THE NORTH. GUIDANCE HAS COME INTO   
MUCH BETTER AGREEMENT IN THE TIMING AND PLACEMENT OF THE DRY AIR,   
WHICH EXTEND OVER NORTHERN MO INTO WEST-CENTRAL IL. WIDESPREAD 30S   
ARE EXPECTED SATURDAY MORNING WITH THE COLDEST TEMPERATURES LINING   
UP WEST TO EAST ALONG AND NORTH OF HWY 36 IN MO AND I-72 IN IL. 50-  
70% OF THE HREF MEMBERS SHOW LOWS AT OR BELOW 32 DEGREES IN THIS   
REGION OF CLEARING AND LIGHT WINDS. SUFFICE TO SAY, TEMPERATURES ARE   
LIKELY TO BRING AN OFFICIAL END TO THE GROWING SEASON. HOWEVER, IF   
KUIN DROPS TO 32 OR COLDER, PERIOD-OF-RECORD DATA SHOWS THIS TO BE   
THE 14TH LATEST FREEZE ON RECORD DATING BACK TO 1901, ALONG WITH THE   
FACT THE AREA HAS DROPPED INTO THE LOW TO MID-30S MULTIPLE TIMES   
ALREADY. MOST GROWING HAS CEASED, FREEZING TEMPERATURES BECOME MORE   
WIDESPREAD SUNDAY MORNING AND TONIGHT'S WINDS STAY ELEVATED ENOUGH   
TO MITIGATE FROST POTENTIAL. THEREFORE, HEADLINE DECISIONS WILL   
FOCUS ON SUNDAY MORNING (SEE NEXT PARAGRAPH) TO SIMPLIFY MESSAGING   
AND PREVENT CONFUSION.   
  
(15Z SATURDAY THROUGH 12Z SUNDAY)  
  
NOVEMBER ARRIVES WITH A WELCOME PACKAGE - COLD AIR ADVECTION WILL BE   
IN FULL SWING UNDER SCATTERED TO BROKEN CLOUDS AND NORTHWEST WINDS.   
AS THE UPPER LOW CONTINUES ON ITS SOUTHEAST PATH, THE 0C 850MB   
ISOTHERM IS PULLED WELL INTO AR/TN AND NORTHERN MS. MID-LEVEL   
TEMPERATURES OF -3 TO -5C ARE BROADLY DISPERSED OVER MO/IL SATURDAY   
THROUGH LATE MORNING SUNDAY. THE COMBINATION WILL MAKE FOR A CHILLY   
DAY WITH A NOTABLY COOLER TREND IN TEMPERATURES. HI-RES (HRRR/RAP)   
AND MEDIUM RANGE (NAM) GUIDANCE HAS COME IN 2-4 DEGREES COLDER,   
INCLUDING A LIMITED SPREAD IN THE NBM IQR DATA. MUCH OF THE ARE   
STRUGGLES TO GET OUT OF THE 40S WITH THE WARMEST LOCATIONS OVER   
SOUTHEAST MO/SOUTHWEST IL AND EVEN THERE THE NUMBER OF HREF MEMBERS   
DROP DRAMATICALLY FOR EVERY DEGREE ABOVE 50, ULTIMATELY REVEALING   
LESS THAN 20% OF THE MEMBERS ARE AT OR ABOVE 55 DEGREES ALONG AND   
SOUTH OF I-44 (MO) AND I-70 (IL). SHOWERS WILL LARGELY BE CONFINED  
TO AND AHEAD OF THE FRONT OVER SOUTHEAST MO AND SOUTHWEST IL,  
WHERE AS MUCH AS 0.10" COULD FALL. FURTHER NORTH OF THE FRONT, THE  
COLD UPPER AIRMASS (-30C AT 500MB) COULD SUPPORT A FEW ISOLATED TO  
PERHAPS SCATTERED SHOWERS BETWEEN 18Z-00Z (DIURNAL PEAK).  
  
CLOUDS BEGIN TO EVACUATE SATURDAY NIGHT AS DRIER AIR MOVES IN BEHIND   
THE EXITING UPPER WAVE. WINDS LIGHTEN AND SURFACE HIGH PRESSURE   
BUILDS FROM THE EASTERN PLAINS INTO CENTRAL MO. COOLING WILL BE MORE   
EFFICIENT UNDER THE SURFACE HIGH, GENERALLY FROM QUINCY TO   
COLUMBIA, WHERE LOWS FALL IN THE UPPER 20S TO LOW-30S. THE   
NOTORIOUSLY COOLER MICROCLIMATES COULD YIELD LOW TO MID-20S WITH   
WIDESPREAD LOW TO MID- 30S. NBM GUIDANCE HAS NUDGED TEMPERATURES   
DOWN ELSEWHERE, TOO, WITH COOLER TRENDS SIGNALING LOW NEAR OR JUST  
BELOW FREEZING THROUGH A LARGE MAJORITY OF THE CWA. COOLER   
TRENDS, CLIMBING HREF PROBABILITIES FOR FREEZING TEMPERATURES, AND  
THE SPREAD OF LOWS AROUND 30 DEGREES ARGUED FOR THE FREEZE WATCH   
TO BE EXPANDED OVER THE ENTIRE CWA LATE SATURDAY NIGHT INTO SUNDAY  
MORNING. THE LATE- SEASON TIMING SHOULD BE A GOOD POINT TO CALL   
AN END TO THE GROWING SEASON, ESPECIALLY CONSIDERING THAT   
TEMPERATURES HAVE BEEN IN THE 30S (WITH FROST) ON MULTIPLE   
OCCASIONS ALREADY.  
  
MAPLES  
  
  
   
LONG TERM  
  (SUNDAY THROUGH NEXT FRIDAY)  
ISSUED AT 245 PM CDT FRI OCT 31 2025  
  
(12Z SUNDAY THROUGH 00Z MONDAY)  
  
THE LONGWAVE TROUGH MOVES EAST THROUGH THE DAY SUNDAY WITH   
NORTHWESTERLY FLOW ALOFT, WHILE AN UPPER RIDGE STAGES TO THE WEST.   
WITH THE RIDGE TO THE WEST, WE WON'T SEE TOO MUCH OF A WARM-UP BUT   
WILL TACK ON A FEW DEGREES OVER SATURDAY'S HIGH TEMPERATURES WITH   
AMPLE SUNSHINE. HIGHS RETURN TO THE LOW TO MID-50S.  
  
(00Z MONDAY THROUGH 12Z WEDNESDAY)  
  
SURFACE HIGH PRESSURE SHIFTS FROM CENTRAL MO INTO WESTERN TN LATE   
SUNDAY INTO MONDAY, TURNING WINDS OUT OF THE SOUTH AND SOUTHWEST.   
MEANWHILE, THE UPPER LEVEL RIDGE BEGINS TO BUILD EASTWARD, AS WELL,   
MARKING THE BEGINNING OF WAA AND A RETURN TO NEAR NORMAL   
TEMPERATURES (LOW TO MID-60S). NBM'S IQR REMAINS TIGHTLY CLUSTERED   
THROUGH MONDAY, BUT THEN BEGINS TO SPREAD TUESDAY. THOUGH GLOBAL   
GUIDANCE HAS COME INTO BETTER AGREEMENT WITH THE SYNOPTIC PATTERN, A   
COUPLE MINOR DISAGREEMENTS CONTINUE TO EXPAND THE SPREAD THROUGH   
WEDNESDAY.   
  
GLOBAL GUIDANCE SHOWS DE-AMPLIFICATION IN THE UPPER RIDGE AS IT   
PROGRESSES EAST LATE MONDAY INTO TUESDAY. ANOTHER SURFACE RIDGE   
QUICKLY BUILDS SOUTHEAST AND EVENTUALLY BECOMES CONJOINED WITH THE   
SURFACE HIGH OVER TN. THE SURFACE HIGH BUILDING DOWN FROM THE   
NORTHWEST FOLLOWS A COLD FRONT THAT ESSENTIALLY WASHES OUT AS THE   
UPPER PATTERN BECOMES MORE ZONAL AND A WEAK SHORTWAVE ROCKETS OVER   
THE REGION FROM WEST TO EAST WITHIN THE ZONAL UPPER LEVEL PATTERN.   
THIS IS NOT AT ALL AN ORGANIZED, NOR STRONG SYSTEM, AND THE AMOUNT   
OF DRY AIR AROUND THE SURFACE RIDGING IS EXPECTED TO KEEP THINGS DRY   
AT THIS TIME. WHILE THERE IS SOME SPREAD IN THE DATA GOING INTO   
MIDWEEK, THE GENERAL THEME SHOULD BE A MODEST STAIR STEP INTO MILDER   
TEMPERATURES THROUGH WEDNESDAY.   
  
(12Z WEDNESDAY THROUGH SATURDAY NIGHT)  
  
WEDNESDAY IS FAVORED TO BE THE MILDEST DAY OF THE WEEK, BUT JUST HOW   
WARM IS STILL IN QUESTION WITH SPREAD INCREASING TO AROUND 7-8   
DEGREES WEDNESDAY AFTERNOON. GLOBAL GUIDANCE SHOWS A WEAK SURFACE   
LOW QUICKLY EJECTING EASTWARD FROM THE NORTHERN ROCKIES, CROSSING   
THE CENTRAL U.S., ALONG WITH A COLD FRONT THAT PRECEDES A SURFACE   
HIGH. GUIDANCE DIVERGES ON BOTH THE SPEED AND PLACEMENT OF THESE   
FEATURES, WHICH DOMINOES ON DOWN THE LINE FROM THERE. THE   
BOUNDARY LINGERS SOMEWHERE IN THE REGION AS IT GETS HUNG UP ON THE  
NORTHWEST SIDE OF RIDGING OVER THE SOUTHEASTERN U.S. EXACTLY HOW   
THIS PLAYS OUT IS LESS CERTAIN AT THIS DISTANCE IN TIME, BUT THE   
PLACEMENT COULD RESULT IN ANYTHING FROM SEASONABLY COOL   
TEMPERATURES TO ABOVE NORMAL TEMPERATURES WITH 10-12 DEGREES   
SEPARATING THE 25TH/75TH PERCENTILES IN THE NBM DATA. YET ANOTHER   
SYSTEM APPROACHES LATE THURSDAY INTO FRIDAY, POTENTIALLY BRING A   
ROUND OF SHOWERS ALONG ANOTHER COLD FRONT FRIDAY. GIVEN THE SPREAD  
THAT DEVELOPS BY MIDWEEK, CONFIDENCE IN THE LATE WEEK ISN'T ANY   
GREATER AT THIS TIME.  
  
MAPLES  
  
  
   
AVIATION  
  (FOR THE 18Z TAFS THROUGH 18Z SATURDAY AFTERNOON)  
ISSUED AT 1234 PM CDT FRI OCT 31 2025  
  
MOSTLY CLEAR SKIES AND LIGHT WINDS WILL GIVE WAY TO MID-LEVEL VFR  
CLOUDS TONIGHT AS A COLD FRONT SINKS SOUTHWARD THROUGH THE REGION.  
THE FRONT ARRIVES AT KUIN JUST AFTER 00Z THIS EVENING, MOVING  
SOUTHWARD THROUGH CENTRAL MO AND METRO TERMINALS AROUND MIDNIGHT.  
WINDS WILL REMAIN LIGHT IN MOST CASES WITH A BRIEF 1-2 HOUR   
WINDOW FOR GUSTS NEAR 20KTS ALONG AND JUST BEHIND THE FRONT. THE  
POTENTIAL IS GREATEST AROUND METRO TERMINALS WITH THE COMPACT  
NATURE OF THE LOW LEVEL JET. NORTHWESTERLY SURFACE FLOW CONTINUE  
THROUGH THE REMAINDER OF PERIOD WITH SCATTERED TO BROKEN VFR  
CEILING FAVORED TO HOLD THROUGH SATURDAY AFTERNOON.  
  
MAPLES  
  
  
   
LSX WATCHES/WARNINGS/ADVISORIES  
  
MO...FREEZE WATCH FROM LATE SATURDAY NIGHT THROUGH SUNDAY MORNING FOR   
     AUDRAIN MO-BOONE MO-CALLAWAY MO-COLE MO-CRAWFORD MO-  
     FRANKLIN MO-GASCONADE MO-IRON MO-JEFFERSON MO-KNOX MO-LEWIS   
     MO-LINCOLN MO-MADISON MO-MARION MO-MONITEAU MO-MONROE MO-  
     MONTGOMERY MO-OSAGE MO-PIKE MO-RALLS MO-REYNOLDS MO-SAINT   
     CHARLES MO-SAINT FRANCOIS MO-SAINT LOUIS CITY MO-SAINT   
     LOUIS MO-SAINTE GENEVIEVE MO-SHELBY MO-WARREN MO-WASHINGTON   
     MO.  
  
IL...FREEZE WATCH FROM LATE SATURDAY NIGHT THROUGH SUNDAY MORNING FOR   
     ADAMS IL-BOND IL-BROWN IL-CALHOUN IL-CLINTON IL-FAYETTE IL-  
     GREENE IL-JERSEY IL-MACOUPIN IL-MADISON IL-MARION IL-MONROE   
     IL-MONTGOMERY IL-PIKE IL-RANDOLPH IL-SAINT CLAIR IL-  
     WASHINGTON IL.  
  
  
  
  
  
WFO LSX  
 
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