165
FXUS63 KLSX 301959
AFDLSX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAINT LOUIS MO
259 PM CDT THU OCT 30 2025
KEY MESSAGES
- SEASONABLY COOL, MOSTLY DRY CONDITIONS ARE EXPECTED OVER THE
NEXT SEVERAL DAYS. THE SOLE CHANCE OF RAIN ACROSS SOUTHEAST
MISSOURI AND SOUTHWEST ILLINOIS IS NEARLY NEGLIGIBLE WITH LOW
CHANCES (25%) AND AMOUNTS (TRACE-0.02") HAVING LIMITED IMPACT.
- TEMPERATURES MODERATE NEXT WEEK WITH SEASONABLY MILD CONDITIONS
CURRENTLY FORECAST WEDNESDAY ONWARD.
SHORT TERM
(THROUGH LATE FRIDAY NIGHT)
ISSUED AT 252 PM CDT THU OCT 30 2025
(CURRENT ANALYSIS THROUGH 00Z THIS EVENING)
REGIONAL SATELLITE SHOWS A CORRIDOR OF CLEARING STRETCHING FROM
LAKE MICHIGAN THROUGH THE GULF REGION, ALL IN BETWEEN A DEPARTING
SYSTEM TO THE EAST AND CLOUD COVER ASSOCIATED WITH A SHORTWAVE TO
OVER IA/MN. DESPITE MOSTLY SUNNY CONDITIONS, COOLER AIR AND
NORTHWEST FLOW HAS HELD TEMPERATURES IN THE 50S UNDER SUNSHINE AND
LOW TO MID-50S OVER NORTHEAST MO, WHERE CLOUD COVER REMAINS. THE
STORY DOESN'T CHANGE MUCH THE REST OF THE AFTERNOON WITH HIGHS
REACHING NEAR 60 DEGREES WHERE SUNSHINE IS MORE PREVALENT AND
MID-50S UNDER CLOUD COVER IN NORTHEAST MO.
(00Z THIS EVENING THROUGH 15Z FRIDAY MORNING)
THE WEAK SHORTWAVE OVER IOWA WILL TRACK SOUTHEAST OVER EASTERN MO
AND IL TONIGHT. ALL GUIDANCE INDICATES A NARROW BAND OF MID-LEVEL
SATURATION CENTERED AROUND 700MB WILL RESIDE NEAR THE 0C 850MB
ISOTHERM THAT WILL LEAD TO MID/HIGH CLOUDS. AS THE SHORTWAVE ROTATES
SOUTHEAST, IT WILL WORK IN TANDEM WITH SURFACE HIGH PRESSURE OVER
THE SOUTHERN PLAINS TO BACK WINDS OUT OF THE WEST AND MOVE CLOUD
COVER TO THE EAST OF THE CWA BETWEEN 05Z-07Z AND LIGHTEN WINDS TO
AROUND 5KTS OR LESS. TEMPERATURES WILL FALL THROUGH THE 40S LATE
THIS EVENING WITH FRIDAY MORNING LOWS IN THE MID-30S TO LOW-40S. THE
COOLEST LOCATIONS WILL BE OVER NORTH-CENTRAL AND NORTHEAST MO, JUST
WEST OF THE INITIAL CLOUD COVER. AIR CONTINUES TO DRY AS DEWPOINTS
IN THE LOW-30S ARE PULLED IN FROM THE CENTRAL PLAINS. HOWEVER,
RECENT RAINFALL HAS MOISTENED THE GROUND LAYER IN RECENT DAYS AND
COULD AID IN PRODUCING PATCHY FROST AT COOLER LOCATIONS. IT DOES NOT
LOOK TO BE A KILLING FROST, HOWEVER, AS POTENTIAL IS MARGINAL WITH
FORECAST LOWS LEANING CLOSER TO THE 25TH PERCENTILE (LOW-30S) VS.
MEAN TEMPERATURES (MID-30S) AND BORDERLINE WINDS (3-6 MPH) THAT
SHOULD MITIGATE WIDESPREAD FROST. HREF ENSEMBLES SHOW LIKELY
PROBABILITIES (60-70%) FOR 12Z TEMPERATURES AT OR BELOW 34 DEGREES
EXTENDING FROM THE IA/MO/IL TRI-STATE REGION THROUGH CENTRAL MO,
PROVIDING ENOUGH CONFIDENCE FOR A FROST ADVISORY 08Z TONIGHT THROUGH
13Z FRIDAY MORNING.
(15Z FRIDAY THROUGH 12Z SATURDAY MORNING)
THE WEAK UPPER LEVEL SHORTWAVE MOVES OVER THE OHIO VALLEY FRIDAY
MORNING INTO FRIDAY AFTERNOON, AS THE NEXT UPPER LEVEL LOW FOLLOWS
CLOSELY BEHIND. A SURFACE LOW ACCOMPANIES THIS NEXT WAVE, BUT TRENDS
WEAKER AS GUIDANCE SIGNALS MODEST HEIGHT RISES AND THE UPPER WAVE
SLOWLY BEGINS TO OPEN AS IT ENTERS NORTHERN IL SATURDAY MORNING. A
SURFACE COLD FRONT RUNS AHEAD OF THE UPPER SYSTEM AND MOVES THROUGH
THE REGION FROM NORTH TO SOUTH LATE FRIDAY INTO FRIDAY NIGHT. OVER
THE LAST COUPLE OF FORECAST CYCLES, NBM PROBABILITIES FOR
PRECIPITATION HAVE BOUNCED BETWEEN SLIGHT CHANCE AND SILENT POPS
(BELOW 15%). MOISTURE IS ALREADY AT A PREMIUM WITH THIS SYSTEM AND
WITH THE FRONT MOVING THROUGH DURING DIURNAL MINS, IT WOULD FAVOR
MOSTLY DRY CONDITIONS. DRY CONDITIONS ARE FAVORED WITH LESS THAN 10%
OF THE LREF MEMBERS SHOWING RAINFALL OVER THE FAR SOUTHERN CWA ALONG
THE COLD FRONT EARLY SATURDAY MORNING.
THE GREATEST IMPACT WILL BE ON TEMPERATURES. QUICKER HI-RES
SOLUTIONS SUGGEST DRY AIR WRAPS IN BEHIND THE COLD FRONT AT THE
SOUTHERN SIDE OF THE APPROACHING UPPER LOW, CLEARING SKIES IN A EAST-
WEST STRETCH FROM CENTRAL IL THROUGH CENTRAL MO. HRRR/RAP/NAM ARE
ALL COOLER THAN THE GFS/ECM, WHILE THE ECM IS A MIDDLE GROUND (MID-
30S) BETWEEN THE GFS AND HI-RES SOLUTIONS. TRENDS BRING A LITTLE
GREATER CONCERN FOR FREEZE POTENTIAL SATURDAY MORNING WITH EVEN
BETTER CHANCES FOR WIDESPREAD FREEZING TEMPERATURES SUNDAY MORNING
(SEE LONG TERM).
MAPLES
LONG TERM
(SATURDAY THROUGH NEXT THURSDAY)
ISSUED AT 252 PM CDT THU OCT 30 2025
(15Z SATURDAY-12Z MONDAY)
LONGWAVE TROUGHING WILL COVER THE EASTERN 2/3RDS OF THE LOWER 48
SATURDAY AS IT CONTINUES TO SHIFT SOUTHEAST THROUGH THE MISSISSIPPI
VALLEY. THE UPPER LOW (MENTIONED IN THE SHORT TERM) IS MORE LIKELY
TO TRACK SOMEWHERE THROUGH NORTHERN IL WITH THE GFS BEING THE
WESTWARD OUTLIER. MEANWHILE, A SECOND WEAKER SHORTWAVE ROUNDS THE
BASE OF THE TROUGH THROUGH EASTERN TX INTO AR AS FRIDAY NIGHT'S COLD
FRONT PROGRESSES INTO THE SOUTHERN SECTIONS OF THE CWA. WHILE
MOISTURE IS LACKING WITH A SHALLOW ~100MB LAYER OF SATURATION
CENTERED AROUND 850MB, MID/UPPER LEVEL ASCENT MAY BE ENOUGH TO POP
OFF A FEW SHOWERS ALONG THE FRONT AS DIURNAL TRENDS TAKE SATURDAY
AFTERNOON/EVENING. NOT MUCH HAS CHANGED ON THIS FRONT WITH LREF IQR
SHOWING A COUPLE HUNDREDTHS OF AN INCH SEPARATING THE 25TH/75TH
PERCENTILES AND MAX AMOUNTS IN SIMILAR TERRITORY. A FEW SHOWERS
AREN'T OUT OF THE QUESTION, BUT IT WON'T BE A WASHOUT BY ANY
MEASURE. EVEN WHERE POPS (25%) LIE ACROSS THE SOUTHERN CWA LATE
SATURDAY, MUCH OF THE TIME WILL REMAIN DRY.
THE BIGGER STORY WILL BE TEMPERATURES WITH A MUCH COOLER AIRMASS
SINKING SOUTHWARD BEHIND THE FRONT. NAM IS A GOOD REFERENCE FOR
TRENDS WITH IT TUCKING BETWEEN THE END OF HI-RES AND LONG RANGE
GUIDANCE WINDOW AND IT HAS SHOWN A TREND TOWARD COOLER 850MB
TEMPERATURES, ESPECIALLY ALONG AND WEST OF THE MISSISSIPPI RIVER.
THIS TREND HAS CONTINUED SINCE THE TIMEFRAME ENTERED THE NAM
TIMEFRAME AT 00Z WEDNESDAY EVENING. THIS IS LIKELY THE PRODUCT OF
THE NORTHEASTERN TRACK OF THE UPPER LOW WITH NORTHWEST, MID-LEVEL
FLOW WRAPPING COOLER AIR FURTHER SOUTH AND EAST THAN PREVIOUS RUNS.
SUNDAY MORNING MAY BE THE FIRST WIDESPREAD FREEZE OF THE SEASON WITH
LOWS PROJECTED TO FALL INTO THE UPPER 20S TO MID-30S. TAKING BOTH
SATURDAY AND SUNDAY MORNING INTO ACCOUNT, IT JUST MAY BE THE
OFFICIAL END OF THE GROWING SEASON WITH A KILLING FREEZING POSSIBLE.
LREF PROBABILITIES (<5%) OF <32 DEGREES DO NOT DO ANY JUSTICE AND
I'M INCLINED TO BELIEVE THESE PROBABILITIES WILL RISE AS THE TIME
PERIOD FALLS INTO THE GRASP OF THE HREF MEMBERS.
(12Z MONDAY-00Z WEDNESDAY)
THE UPPER LEVEL WAVE CONTINUES TO MOVE EAST INTO THE MID-ATLANTIC
REGION EARLY MONDAY AS ONE SURFACE HIGH MOVES INTO THE GULF REGION
AND IS REPLACED BY A SECOND SURFACE HIGH FROM THE NORTHERN PLAINS.
UPPER LEVEL RIDING BEGINS TO BUILD EASTWARD WITH INITIAL RETURN FLOW
BEHIND THE SOUTHERN SURFACE HIGH TURNING NORTHWESTERLY AHEAD OF THE
SECOND HIGH MONDAY AFTERNOON. ALL THAT SAID, MID-LEVEL TEMPERATURES
WARM BY 5-8C MONDAY MORNING AS A MID-LEVEL TROUGH AND SURFACE COLD
FRONT BRING A REINFORCEMENT OF COOLER AIR. THE COLDEST OF THE AIR
REMAINS NORTH OF THE CWA WITH THE THEME MORE SO BEING A TEMPORARY
SUPPRESSION OF MILDER AIR TO THE SOUTH. TEMPERATURES WILL MODERATE
AND REMAIN PRETTY STABLE THROUGH TUESDAY WITH HIGHS IN THE 60S AND
LOWS IN THE MID-30S TO LOW-40S.
(00Z WEDNESDAY-00Z FRIDAY)
NBM DATA BEGINS TO DIVERGE MIDWEEK AND BEYOND WITH RIDGING TO THE
WEST AND ACTIVE PATTERN TO THE NORTH. THE MID-MISSISSIPPI VALLEY
LIES AT THE SOUTHERN END OF THE ACTIVE TRACK TO THE NORTH, WHICH AT
TIMES BRINGS SOME INFLUENCE OF COOLER AIR FROM THE NORTH AND
NORTHWEST OR MILDER AIR FROM WEST AND SOUTHWEST. THE PATTERN SETS UP
SUCH THAT A SHIFT IN EITHER DIRECTION COULD RESULT IN SEASONABLE
TEMPERATURES OR WARMER THAN NORMAL CONDITIONS. TRENDS DO FAVOR A
SLIGHTLY WARM PATTERN WITH HIGHS APPROACHING 70 DEGREES FROM MID TO
LATE WEEK.
MAPLES
AVIATION
(FOR THE 18Z TAFS THROUGH 18Z FRIDAY AFTERNOON)
ISSUED AT 1226 PM CDT THU OCT 30 2025
MID/HIGH VFR CLOUDS WILL PUSH WEST TO EAST OVER MISSOURI THIS
EVENING AND INTO ILLINOIS JUST BEFORE MIDNIGHT TONIGHT. OTHERWISE,
MOSTLY CLEAR SKIES ARE EXPECTED WITH NORTHWEST WINDS BACKING OUT
OF THE WEST THROUGH FRIDAY MORNING. TYPICAL DIURNAL TRENDS WILL
INCREASE WINDS SPEEDS TO 10-15 KTS THROUGH THE DAYLIGHT HOURS
WITH AN OCCASIONAL 18-20 KT GUST NORTH OF THE METRO TERMINALS
THROUGH KUIN. HOWEVER, GUST MAGNITUDE AND OCCASIONAL OCCURRENCE
WAS NOT ENOUGH TO ACCOUNT FOR IN THE PREVAILING GROUPS AT KUIN.
COOLER NIGHTTIME TEMPERATURES MAY ALSO RESULT IN SOME STEAM FOG ON
AREA RIVERS. THE LIGHT WIND AND WESTERLY COMPONENT SHOULD KEEP
KSUS IN THE CLEAR WHILE KJEF HAS A LITTLE BETTER POTENTIAL BEING
EAST OF THE MO RIVER. CONSIDERING THE DRY AIR AND WIND COMPONENT,
THERE WASN'T ENOUGH CONFIDENCE TO INCLUDE IN THE TAF AT THIS TIME.
VFR CONDITIONS ARE FAVORED THROUGHOUT THE PERIOD AT THIS TIME.
MAPLES
LSX WATCHES/WARNINGS/ADVISORIES
MO...FROST ADVISORY FROM 3 AM TO 8 AM CDT FRIDAY FOR AUDRAIN MO-BOONE
MO-CALLAWAY MO-COLE MO-CRAWFORD MO-FRANKLIN MO-GASCONADE MO-
IRON 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 FRANCOIS MO-SHELBY MO-WARREN MO-
WASHINGTON MO.
IL...FROST ADVISORY FROM 3 AM TO 8 AM CDT FRIDAY FOR ADAMS IL-BROWN
IL-PIKE IL.
WFO LSX
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