870
FXUS63 KLSX 311115
AFDLSX
AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE SAINT LOUIS MO
615 AM CDT FRI OCT 31 2025
KEY MESSAGES
- COOL AND LARGELY DRY CONDITIONS ARE EXPECTED THROUGH THIS
WEEKEND. A FREEZE ADVISORY IS IN EFFECT IN MOST OF THE EASTERN
HALF OF MISSOURI AND IN WEST-CENTRAL ILLINOIS SUNDAY NIGHT.
- A WARM-UP IS FORECAST TO BEGIN ON MONDAY. MOST LOCATIONS SOUTH
OF I-70 HAVE A >50% CHANCE AT SEEING HIGHS IN THE LOW 70S ON
WEDNESDAY.
SHORT TERM
(THROUGH LATE SATURDAY AFTERNOON)
ISSUED AT 344 AM CDT FRI OCT 31 2025
DESPITE THE COLD START TO THE MORNING, ABUNDANT SUNSHINE AND WEAK
WARM AIR ADVECTION WILL MAKE TODAY SLIGHTLY WARMER THAN YESTERDAY
FOR MOST OF THE CWA. MOST LOCATIONS ARE FORECAST TO HIT AT LEAST 60
DEGREES, WITH PORTIONS OF SOUTHEAST MISSOURI APPROACHING 65. THE
EXCEPTION TO TODAY'S 60S HIGHS LIE IN NORTHEAST MISSOURI AND WEST-
CENTRAL ILLINOIS WHERE CLOUD COVER AHEAD OF AN INCOMING MID-LEVEL
LONGWAVE TROUGH WILL KEEP HIGHS IN THE UPPER 50S.
THIS TROUGH WILL PUSH A COLD FRONT THROUGH THE MID-MISSISSIPPI
VALLEY TONIGHT. WITH LITTLE MOISTURE PRESENT AND A NOCTURNAL
PASSAGE, RAIN CHANCES REMAIN VERY LOW (<20%) FOR TONIGHT. CHANCES
INCREASE SLIGHTLY (20-30%) IN SOUTHWEST ILLINOIS AND SOUTHEAST
MISSOURI SATURDAY AFTERNOON AS MORE POTENT MID-LEVEL FORCING
INCREASES COVERAGE ALONG THE FRONT. HOWEVER, RECENT TRENDS HAVE BEEN
PUSHING THE FRONT OUT OF OUR CWA BY THIS POINT, SO WE'RE UNLIKELY TO
REAP ANY BENEFITS. INCOMING MOISTURE ASSOCIATED WITH THE CLOSED
UPPER LOW DOES PROVIDE MUCH MORE OF THE AREA WITH A SLIGHT CHANCE OF
LIGHT RAIN SATURDAY AFTERNOON, BUT MOST LOCATIONS WILL STAY DRY.
THE LARGER IMPACT OF THE COLD FRONT WILL BE THE ARRIVAL OF COOLER
AIR, BUT THERE IS UNCERTAINTY REGARDING HOW COOL PORTIONS OF
NORTHEAST MISSOURI AND WEST-CENTRAL ILLINOIS BECOME TONIGHT.
BECAUSE OF THIS, WE'VE HELD OFF ON ISSUING A FROST ADVISORY OR
FREEZE WATCH FOR TONIGHT. IF THE CLOUDS ASSOCIATED WITH THE FRONT
ARE SLOWER TO EXIT OR TREND FURTHER NORTH, FROST WILL NOT FORM AND
TEMPERATURES COULD WARM AS MUCH AS 5 DEGREES. A SIMILAR SOLUTION
IS TRUE IF CLOUDS TO OUR NORTH ARE QUICKER TO ARRIVE OR TREND
FURTHER SOUTH. CONFIDENCE IS MUCH HIGHER IN THE LOW TEMPERATURE
FORECAST FOR SATURDAY NIGHT/SUNDAY MORNING, AND THUS A FREEZE
WATCH HAS BEEN ISSUED FOR MOST OF EASTERN MISSOURI AND PORTIONS OF
WEST-CENTRAL ILLINOIS. CONSENSUS AMONG GUIDANCE IS THAT HIGH
PRESSURE WILL CENTER VERY CLOSE TO IF NOT WITHIN THE CWA SUNDAY
NIGHT, ALLOWING SKIES TO CLEAR AND RADIATIONAL COOLING TO TAKE
EFFECT. THE LOCATIONS MENTIONED HAVE SPREADS OF ~3 DEGREES WITH
THEIR NBM 25TH/75TH PERCENTILE LOWS WITH THE WARMEST 75TH
PERCENTILE TEMPERATURE BEING 34 DEGREES. GIVEN THE NBM'S WARM BIAS
AND REALITY OFTEN BEING BETTER REFLECTED BY THE 25TH PERCENTILE
DURING RADIATIONAL COOLING EVENTS, I HAVE VERY HIGH CONFIDENCE IN
A WIDESPREAD FREEZE OCCURRING SUNDAY MORNING.
JAJA
LONG TERM
(SATURDAY NIGHT THROUGH THURSDAY)
ISSUED AT 344 AM CDT FRI OCT 31 2025
UPPER LEVEL RIDGING WILL BUILD IN BRIEFLY ON MONDAY, BUT IT WON'T
STAY FOR LONG. DETERMINISTIC GUIDANCE SHOWS A DYNAMIC UPPER LEVEL
FLOW MARKED BY MULTIPLE SHORTWAVES GLIDING THROUGH THE REGION
THROUGH NEXT WEEKEND. THESE SHORTWAVES WILL FAIL TO IMPACT OUR
SENSIBLE WEATHER BEYOND ADDITIONAL CLOUD COVER DUE TO DRY AIR IN
PLACE. A MORE POTENT TROUGH ENTERING THE MID-MISSISSIPPI VALLEY LATE
NEXT WEEK MAY THREATEN THIS REGIME.
DRY AIR IN PLACE, INSOLATION, AND SOME WARM AIR ADVECTION WILL ALLOW
THE REGION TO WARM NEXT WEEK, THOUGH TO WHAT DEGREE IS UNCERTAIN.
LOW NBM 25TH/75TH PERCENTILE SPREADS ON MONDAY AND TUESDAY GIVE
CONFIDENCE TO HIGH TEMPERATURES CLIMBING INTO THE 60S. BEYOND THAT,
MULTIPLE COLD FRONTS ASSOCIATED WITH PASSING SHORTWAVES THWART THE
TEMPERATURE FORECAST BOTH IN WARM AND COOL DIRECTIONS THROUGH THE
WEEK. THIS IS DUE TO UNCERTAINTIES IN HOW MUCH WARM AIR WILL BE
PULLED INTO THE REGION AHEAD OF A FRONT, HOW MUCH COLD AIR WILL
FOLLOW IT, WHAT TIME EACH COLD FRONT PASSES, ETC., WHICH ALL STEM
FROM THE CHARACTERISTICS OF EACH SHORTWAVE.
JAJA
AVIATION
(FOR THE 12Z TAFS THROUGH 12Z SATURDAY MORNING)
ISSUED AT 613 AM CDT FRI OCT 31 2025
AFTER PATCHY FOG BURNS OFF SHORTLY AFTER SUNRISE, DRY AND VFR
CONDITIONS WILL PREVAIL THROUGH THE TAF PERIOD.
JAJA
LSX WATCHES/WARNINGS/ADVISORIES
MO...FROST ADVISORY UNTIL 8 AM CDT THIS MORNING 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.
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-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 UNTIL 8 AM CDT THIS MORNING FOR ADAMS IL-BROWN IL-
PIKE IL.
FREEZE WATCH FROM LATE SATURDAY NIGHT THROUGH SUNDAY MORNING FOR
ADAMS IL-BROWN IL-PIKE IL.
WFO LSX
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