539
FXUS63 KLSX 271900
AFDLSX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAINT LOUIS MO
200 PM CDT MON OCT 27 2025
KEY MESSAGES
- WIDESPREAD BENEFICIAL RAIN IS EXPECTED (90 - 100% CHANCE)
TOMORROW THROUGH WEDNESDAY. MOST OF THE AREA HAS A 70 - 80%
CHANCE AT SEEING 0.50" OR MORE RAIN.
- COOL, DRY WEATHER WILL END THIS WEEK.
SHORT TERM
(THROUGH LATE TUESDAY NIGHT)
ISSUED AT 156 PM CDT MON OCT 27 2025
TONIGHT WILL BE THE WARMEST NIGHT THROUGH AT LEAST LATE THIS WEEK AS
LOW CLOUD COVER KEEPS THE REGION INSULATED. MOST LOCATIONS WILL SEE
LOWS IN THE 40S, WHICH, DESPITE FEELING CHILLY, IS ACTUALLY 5 - 10
DEGREES ABOVE AVERAGE FOR LATE OCTOBER. THE NIGHTLY "WARMTH" WON'T
LAST LONG, HOWEVER, AS OUR NEXT SYSTEM WILL USHER IN COOLER AIR AS
WELL AS WIDESPREAD RAIN.
WATER VAPOR IMAGERY SHOWS THE BEGINNINGS OF OUR AFOREMENTIONED NEXT
SYSTEM IN THE FORM OF AN UPPER-LEVEL TROUGH SWIRLING OVER THE
NORTHERN PLAINS AND PACIFIC NORTHWEST. THIS FEATURE WILL DIG INTO
THE CENTRAL PLAINS AND MID-MISSISSIPPI VALLEY OVERNIGHT, WHILE AT
THE SURFACE A COLD FRONT GAINS INTENSITY AND APPROACHES MISSOURI
FROM THE WEST. CYCLOGENESIS ALONG THE FRONT CAUSED BY UPPER LEVEL
DYNAMICS WILL RESULT IN THE FRONT TILTING FROM NEAR VERTICAL TO A
MORE NORTHWESTERLY-SOUTHEASTERLY ORIENTATION AS IT ENTERS THE CWA
LATE TUESDAY AFTERNOON INTO EVENING. THE DEEPENING SURFACE LOW IS
FORECAST TO TRACK EITHER IN OUR SOUTHERN CWA OR JUST SOUTH OF IT,
LEAVING AT LEAST OUR SOUTHERN COUNTIES BELOW THE SYSTEM'S WARM
CONVEYOR BELT BY WEDNESDAY MORNING. IN THIS REGION, THE BETTER
DYNAMICS WILL SUPPORT HEAVIER RAINFALL AND PERHAPS A RUMBLE OF
THUNDER. THE LREF AND NBM ENSEMBLES REFLECT THIS, SHOWING THAT
LOCATIONS WITHIN THE WARM CONVEYOR BELT (DEPICTED AS SOUTH OF I-44,
BUT SUBJECT TO CHANGE BASED ON WHERE THE LOW TRACKS) HAVE UP TO A
50% CHANCE OF SEEING 1.00" OF RAIN OVER A 24 HOUR PERIOD WITH THE
SYSTEM. THOUGH THE PROBABILITIES FOR 1.00" DROP DRAMATICALLY
ELSEWHERE, THE ENTIRE CWA HAS A HIGH CHANCE (70 - 80%) OF SEEING >=
0.50" OF RAIN IN THE 24 HOURS BETWEEN TUESDAY AND WEDNESDAY EVENING.
THIS WILL BE BENEFICIAL CONSIDERING THE VAST MAJORITY OF THE CWA IS
IN MODERATE OR SEVERE DROUGHT.
THE COOLER AIR USHERED IN WITH THE FRONT WON'T BE EXTREMELY POTENT.
850 MB TEMPERATURES ARE ONLY FORECAST TO DROP ABOUT 4C, WHICH WILL
TRANSLATE TO US DROPPING FROM ABOUT 55 - 60 DEGREE HIGHS ON TUESDAY
TO 50 - 55 DEGREE HIGHS ON WEDNESDAY. IT WILL LIKELY FEEL MUCH
COOLER TO ANYONE UNFORTUNATE ENOUGH TO STEP OUTSIDE, HOWEVER, GIVEN
THE COOL RAIN AND GUSTY (25 - 30 MPH) PRESSURE GRADIENT WINDS.
JAJA
LONG TERM
(WEDNESDAY THROUGH NEXT MONDAY)
ISSUED AT 156 PM CDT MON OCT 27 2025
THURSDAY THROUGH SATURDAY ARE FORECAST TO BE DRY AND COOL WITH HIGHS
LARGELY IN THE 50S AND LOWS IN THE 30S. DEPENDING ON HOW A SURFACE
HIGH IN THE PLAINS BEHAVES LATE THIS WEEK INTO THIS WEEKEND, WINDS
MAY BECOME LIGHT ENOUGH AT NIGHT TO SUPPORT FROST AGAIN. THIS IS NOT
WRITTEN IN STONE YET, BUT IS A POSSIBILITY CONSIDERING THE 50 - 60%
NBM PROBABILITIES OF TEMPERATURES LESS THAN 36 DEGREES IN PORTIONS
OF THE AREA EACH MORNING.
ANOTHER COLD FRONT IS FORECAST TO DIVE THROUGH THE REGION THIS
WEEKEND, BUT RAIN CHANCES WITH THIS FRONTAL PASSAGE ARE MINIMAL.
MOST OF THE MOISTURE IN OUR CWA WILL BE SCOURED OUT BEHIND THE MID-
WEEK SYSTEM, LEAVING THIS WEEKEND'S COLD FRONT LITTLE TO WORK WITH.
THE COLD FRONT DOES LOOK TO USHER IN ANOTHER BOUT OF COOL AIR,
THOUGH UNCERTAINTY LIES IN HOW POTENT AND LONG-LASTING IT IS. THIS
IS REFLECTED WELL IN A 10 DEGREE SPREAD IN THE NBM HIGH TEMPERATURE
INTERQUARTILE RANGE FOR SUNDAY.
JAJA
AVIATION
(FOR THE 18Z TAFS THROUGH 18Z TUESDAY AFTERNOON)
ISSUED AT 1230 PM CDT MON OCT 27 2025
PERIODS OF DRIZZLE ARE EXPECTED TO DISSIPATE EARLY THIS
AFTERNOON, LEAVING DRY CONDITIONS UNTIL AT LEAST TOMORROW MORNING.
WIDESPREAD RAIN IS EXPECTED TO NEAR CENTRAL MISSOURI TOMORROW, SO
ADDED PROB30S FOR THE END OF THE PERIOD.
MORE NOTABLY, PESKY STRATUS CONTINUES TO SIT ATOP THE CWA WITH THE
GRADIENT BETWEEN MVFR AND IFR SITTING BASICALLY RIGHT OVER THE ST.
LOUIS METROPOLITAN TERMINALS. FOR THIS REASON, CEILINGS MAY BOUNCE
BETWEEN SUB-1000 FT AND 1000-1500 FT UNTIL LATE TONIGHT WHEN IFR
CEILINGS SPREAD NORTH AGAIN. MODELS SUGGEST WIDESPREAD LIFR
OVERNIGHT, BUT HOLDING OFF ON LOCKING THAT IN UNTIL NEWER GUIDANCE
COMES IN.
JAJA
LSX WATCHES/WARNINGS/ADVISORIES
MO...NONE.
IL...NONE.
WFO LSX
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