188
FXUS63 KLSX 161748
AFDLSX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ST LOUIS MO
1248 PM CDT FRI OCT 16 2026
KEY MESSAGES
- A FROST ADVISORY IS IN EFFECT FRIDAY NIGHT ACROSS PORTIONS OF
NORTHEASTERN MISSOURI AND WEST-CENTRAL ILLINOIS WHERE
CONFIDENCE IS HIGHEST IN WIDESPREAD TEMPERATURES IN THE MID
30S.
SHORT TERM /THROUGH SATURDAY NIGHT/
ISSUED AT 215 AM CDT FRI OCT 16 2026
A HIGHLY AMPLIFIED TROUGH CAN BE SEEN IN WATER VAPOR IMAGERY
CURRENTLY DIGGING EQUATORWARD INTO THE MIDWEST. THE COLD FRONT
ASSOCIATED WITH THIS TROUGH AND THE ONE RESPONSIBLE FOR YESTERDAY'S
RAIN HAS CLEARED THE CWA TO THE SOUTHEAST, WITH DEEPENING
NORTHWESTERLY FLOW USHERING IN A FALL-LIKE AIR MASS. THIS AIR MASS
WILL BRING NOTABLY COOLER TEMPERATURES COMPARED TO WHAT WE'VE BEEN
EXPERIENCING AS OF LATE, WITH A MUTED DIURNAL CURVE TODAY LEADING TO
TEMPERATURES TOPPING OUT IN THE LOW TO MID 50S; SOME 20-30 DEGREES
COOLER THAN VALUES ON THURSDAY. DRY CONDITIONS ARE EXPECTED FOR
MOST LOCATIONS TODAY, WITH THE AXIS OF THE UPPER-LEVEL TROUGH
ONLY PRODUCING A 20- 30% CHANCE OF LIGHT RAIN FOR AREAS EAST OF
THE MISSISSIPPI RIVER AS IT PIVOTS OVERHEAD DURING THE
AFTERNOON.
TONIGHT, HIGH PRESSURE AT THE SURFACE WILL SETTLE INTO THE CENTRAL
AND SOUTHERN PLAINS; NOSING INTO THE MIDDLE MISSISSIPPI VALLEY. AS A
RESULT, THE PRESSURE GRADIENT WILL SLACKEN AND WINDS BECOME LIGHT TO
CALM AS SKIES GRADUALLY CLEAR FROM NORTH TO SOUTH. THIS WILL MAKE
FOR IDEAL FROST CONDITIONS ACROSS PORTIONS OF NORTHEASTERN MISSOURI
AND WEST-CENTRAL ILLINOIS, WHERE RADIATIONAL COOLING WILL ALLOW FOR
WIDESPREAD LOWS IN THE MID-30S - THE TEMPERATURE THRESHOLD
GENERALLY NEEDED FOR FROST DEVELOPMENT. WHERE CONFIDENCE IS
HIGHEST IN THESE CONDITIONS OCCURRING, A FROST ADVISORY IS NOW
IN EFFECT LATE FRIDAY NIGHT THROUGH EARLY SATURDAY MORNING.
THANKS TO THE UPPER-LEVEL TROUGH MOVING FURTHER EASTWARD OF THE
REGION SATURDAY, LOW TO MID-LEVEL TEMPERATURES WILL BOUNCE BACK BY A
FEW DEGREES C COMPARED TO THEIR FRIDAY MINIMUM. BETWEEN THIS AND
CLEAR SKIES ALLOWING FOR ABUNDANT INSOLATION, AFTERNOON TEMPERATURES
WILL WARM TO AROUND 60 DEGREES, WHICH IS STILL ABOUT 10 DEGREES
BELOW SEASONAL NORMALS. THERE IS A LOW THREAT (40%) FOR ADDITIONAL
FROST ACROSS PORTIONS OF SOUTHEASTERN MISSOURI AND SOUTHWESTERN
ILLINOIS SATURDAY NIGHT, AND WILL BE DEPENDENT ON WHERE THE
AFOREMENTIONED SURFACE HIGH IS RELATIVE TO THE CWA THEN.
LONG TERM /SUNDAY THROUGH FRIDAY/
ISSUED AT 215 AM CDT FRI OCT 16 2026
THANKS TO CONSENSUS AMONG ENSEMBLE CLUSTERS AND DETERMINISTIC
GUIDANCE, CONFIDENCE IS HIGH IN A BENIGN AND UNEVENTFUL PATTERN
THROUGH THE UPCOMING WORKWEEK. CONTINUOUS TROUGHING OVER THE WEST
COAST AND RIDGING TO OUR EAST-SOUTHEAST WILL KEEP UPPER-LEVEL FLOW
WEAKLY SOUTHWESTERLY THROUGH THIS PORTION OF THE PERIOD. THIS
SUPPORTS WARM AIR ADVECTION, THOUGH SUBTLY GIVEN THE WEAKNESS OF THE
FLOW. AS A RESULT, DAILY TEMPERATURES WILL ONLY GRADUALLY WARM
THROUGH THE WORKWEEK. VALUES CLOSER TO SEASONAL NORMALS ARE AT LEAST
EXPECTED THROUGH THE FIRST HALF OF THE WORKWEEK, BUT HOW MUCH WARMER
WE CLIMB TOWARD THE END OF THE WEEK IS UNCERTAIN. THE NBM
PUSHES AFTERNOON HIGHS TO AROUND 80 DEGREES THURSDAY AND FRIDAY,
THOUGH THAT IS ROUGHLY 5 DEGREES WARMER THAN THE 75TH
PERCENTILE OF ENSEMBLE GUIDANCE. THIS IS DUE TO THE BIAS-
CORRECTED GUIDANCE COMPOSING THE NBM, AND THIS GUIDANCE IS
SEVERAL DEGREES WARMER THAN THEIR NON-BIASED COUNTERPARTS. GIVEN
THE BIAS FACTOR APPLIED HERE MAY BE TOO WARM GIVEN OUR SEASONAL
COOLING, CONFIDENCE IS LOW IN THE NBM'S LATE-WEEK TEMPERATURE
FORECAST.
GIVEN THE WEAKNESS OF THE FLOW ALOFT AND LACK OF ANY NOTABLE
DISTURBANCES IN DETERMINISTIC GUIDANCE, CONFIDENCE IS HIGH IN DRY
CONDITIONS PREVAILING THROUGH THIS PORTION OF THE PERIOD. THIS IS
SUPPORTED BY NEARLY ALL ENSEMBLE MEMBERS SHOWING THIS STRETCH BEING
RAIN-FREE.
AVIATION /18Z TAFS THROUGH 00Z SUNDAY/
ISSUED AT 1247 PM CDT FRI OCT 16 2026
LOW STRATUS ASSOCIATED WITH AN UPPER-LEVEL TROUGH IS IMPACTING
THE REGION CREATING MVFR CEILINGS. THESE MVFR CEILINGS ARE TO
THE NORTHWEST OF THE ST. LOUIS METRO TERMINALS, BUT ARE MOVING
TO THE SOUTHEAST AND WILL IMPACT THE TERMINALS THIS AFTERNOON.
THERE ARE SOME ISOLATED SHOWERS THAT COULD IMPACT THE ST. LOUIS
METRO TERMINALS, BUT CONFIDENCE IS LOW THAT THEY WILL BE
DIRECTLY IMPACTED. AS A RESULT, VCSH WAS INCLUDED TO ACCOUNT FOR
THE POSSIBILITY. WINDS AT ALL TERMINALS ARE EXPECTED TO REMAIN
GUSTY THROUGH THE DAY. AS HIGH PRESSURE MOVES INTO THE REGION
FROM THE WEST OVERNIGHT, WINDS WILL BECOME CALM AND THE CEILINGS
WILL RISE TO VFR EVENTUALLY GIVING WAY TO CLEAR SKIES.
LSX WATCHES/WARNINGS/ADVISORIES
MO...FROST ADVISORY FROM 1 AM TO 9 AM CDT SATURDAY FOR MOZ018-019-
026-027-034>036-042-052.
IL...FROST ADVISORY FROM 1 AM TO 9 AM CDT SATURDAY FOR ILZ058>060-
095>099.
SHORT TERM...ELMORE
LONG TERM...ELMORE
AVIATION...ASEL/BSH
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