252
FXUS63 KLSX 241053
AFDLSX
AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE SAINT LOUIS MO
453 AM CST SAT JAN 24 2026
KEY MESSAGES
- A MAJOR WINTER STORM REMAINS ON TRACK TO IMPACT OUR AREA TODAY
THROUGH TOMORROW MORNING, WITH THE MOST SIGNIFICANT IMPACTS
EXPECTED OVERNIGHT AND TOMORROW MORNING DUE TO HEAVY SNOW. WHILE
THE MAJORITY OF THE AREA WILL SEE ENOUGH SNOW TO IMPACT TRAVEL,
THE MOST SIGNIFICANT IMPACTS ARE EXPECTED ACROSS THE SOUTHERN
HALF OF MISSOURI AND ILLINOIS.
- BITTER COLD TEMPERATURES AND WIND CHILLS WILL LARGELY CONTINUE
THROUGH MONDAY. SOME BRIEF MODERATION IS LIKELY TUESDAY AND
WEDNESDAY DURING THE DAY, BUT MORE COLD AIR ARRIVES OVER THE
LATTER HALF OF THE WEEK, CAUSING SNOW TO REMAIN ON THE GROUND
THROUGH AT LEAST THE END OF THE WEEK IN MANY AREAS.
SHORT TERM
(THROUGH LATE SUNDAY AFTERNOON)
ISSUED AT 349 AM CST SAT JAN 24 2026
WHILE THERE HAVE BEEN SOME SLIGHT CHANGES TO THE TIMING AND
DISTRIBUTION OF SNOW AMOUNTS IN THE LATEST FORECAST, FOR THE MOST
PART WE REMAIN ON TRACK TO SEE A SIGNIFICANT WINTER STORM ACROSS OUR
AREA BETWEEN LATER THIS MORNING AND SUNDAY MORNING. THIS INCLUDES
HEAVY SNOW IN MANY AREAS, PARTICULARLY ACROSS THE SOUTHERN HALF OF
MISSOURI AND ILLINOIS.
AS WE APPROACH THE ONSET OF OUR MUCH-ANTICIPATED WINTER STORM, VERY
COLD AND DRY LOW LEVEL AIR IS FIRMLY IN PLACE ACROSS MUCH OF
MISSOURI AND ILLINOIS, WITH ACTUAL TEMPERATURES GENERALLY BETWEEN 5
DEGREES ABOVE AND BELOW ZERO, AND WIND CHILLS OF ROUGHLY 5 AND 20
BELOW. MEANWHILE, SURFACE DEWPOINTS IN OUR FORECAST AREA REMAIN VERY
LOW, WITH OBSERVATIONS GENERALLY BETWEEN 10 AND 20 DEGREES BELOW
ZERO. EVEN WITH THE NEAR ZERO SURFACE TEMPERATURES, THESE EXTREMELY
LOW DEWPOINTS ARE MAINTAINING RELATIVE HUMIDITY VALUES OF ROUGHLY 30
TO 50 PERCENT, WHICH IS DIFFICULT TO ACHIEVE WITH SUCH COLD ACTUAL
TEMPERATURES. BELIEVE IT OR NOT, THOUGH, THIS IS ACTUALLY SLIGHTLY
LESS DRY THAN MOST MODELS PROJECTED, AND THIS IS EVIDENT IN 00Z-03Z
SOUNDINGS AT SGF AND COU (MIZZOU). IT'S STILL PLENTY DRY ENOUGH TO
EAT INTO INITIAL SNOW TOTALS, BUT NOT QUITE AS INSURMOUNTABLE AS
SOME DATA SUGGESTED, AND AS A RESULT WE ARE ALREADY SEEING SOME
LIGHT ACCUMULATING SNOW IN PARTS OF WESTERN AND SOUTHWESTERN
MISSOURI OVERNIGHT.
AS THE MORNING WEARS ON, MODEST ISENTROPIC LIFT WILL CONTINUE TO
STEADILY INCREASE, AND SNOW WILL GRADUALLY EAT WAY AT THE LAST OF
THIS DRY LAYER. ONCE IT DOES, LIGHT FLUFFY SNOW IS EXPECTED TO
SPREAD INTO MOST OF THE AREA, ALTHOUGH LIKELY NOT ALL AT ONCE, AND
NOT EVENLY DISTRIBUTED. MODEL SOUNDINGS CONTINUE TO SUGGEST THAT
ONCE THE COLUMN SATURATES, MUCH OF THE CLOUD LAYER WILL FIT WITHIN
THE DENDRITIC GROWTH ZONE INITIALLY (-10 TO -20C), ESPECIALLY IN
THE NORTHERN HALF OF THE AREA, WHICH WILL SUPPORT VERY EFFICIENT
SNOW TO LIQUID RATIOS, PERHAPS NEAR OR ABOVE 20 TO 1. SO WHILE
SNOW RATES ARE NOT EXPECTED TO BE VERY HIGH (.5 INCH PER HOUR OR
LESS) AND IT WILL LIKELY STILL TAKE UNTIL EARLY AFTERNOON BEFORE
IT STARTS ACCUMULATING IN OUR NORTHERNMOST AREAS, THIS COULD
QUICKLY YIELD 1 TO 4 INCHES OF VERY FLUFFY SNOW ONCE IT FINALLY
BREAKS THROUGH THIS DRY LAYER IN THE LOW LEVELS. MEANWHILE, THE
ORIGINAL THINKING THAT TODAY WOULD FEATURE A DISTINCT LULL IN
PRECIPITATION APPEARS TO BE LESS SOUND, AS MORE RECENT DATA
SUGGESTS THAT LIGHT SNOW MAY PERSIST WELL INTO THE EVENING IN MANY
AREAS UNTIL THE NEXT SURGE IN SNOW ARRIVES RIGHT BEHIND IT
OVERNIGHT. OVERALL, THE HIGHEST SNOW AMOUNTS (2 TO 4 INCHES) WITH
THE INITIAL ROUND CONTINUE TO BE FAVORED IN CENTRAL AND SOUTHEAST
MISSOURI, BUT SNOW MAY BE MORE EVENLY DISTRIBUTED ACROSS THE AREA
TODAY THAN IT WILL BE DURING THE SECOND ROUND LATER TONIGHT.
OVERNIGHT, A POSITIVELY TILTED SHORTWAVE WILL KICK OUT OF THE
SOUTHERN/CENTRAL PLAINS AND ACROSS OUT AREA, BRINGING WITH IT A
SUBSTANTIAL BOOST IN MID LEVEL (500-700MB) FRONTOGENESIS AND OMEGA,
ALONG WITH INCREASING WARM AIR ADVECTION ALOFT. AS THIS OCCURS,
SNOWFALL RATES ARE EXPECTED TO INCREASE SUBSTANTIALLY, AND MOST
NOTABLY ACROSS THE SOUTHERN HALF OF MISSOURI AND ILLINOIS. IT IS
DURING THIS PERIOD THAT THE HEAVIEST SNOW OF THE EVENT IS EXPECTED
TO FALL, ALTHOUGH THIS WILL NOT BE EVENLY DISTRIBUTED ACROSS THE
AREA, AND WE MAY SEE A REDUCTION IN SNOW TO LIQUID RATIOS IN SOME
PLACES THANKS TO THE AFOREMENTIONED WARM AIR ADVECTION ALOFT.
IN TERMS OF THE DISTRIBUTION OF SNOW, MODEL GUIDANCE CONTINUES TO
TIGHTEN THE GRADIENT OF ACCUMULATING PRECIPITATION ALONG ITS
NORTHERN FLANK, AND SO MUCH SO THAT PARTS OF NORTHEAST MISSOURI AND
WEST-CENTRAL ILLINOIS MAY END UP SEEING LITTLE, IF ANY, NEW
ACCUMULATING SNOW WITH THE SECOND ROUND. IN FACT, IT'S ENTIRELY
POSSIBLE THAT PARTS OF THIS AREA MAY NOT SEE ANY NEW SNOW AFTER THIS
EVENING, OR PERHAPS EVEN NOT MUCH AT ALL IF DRY AIR WINS OUT DURING
THE INITIAL ROUND. THIS IS GENERALLY IN THE AREAS WHERE THE WINTER
WEATHER ADVISORY IS CURRENTLY IN EFFECT, WHICH REFLECTS THE LOWER
CEILING IN POTENTIAL SNOW AMOUNTS, AND LOWER CONFIDENCE IN IMPACTFUL
AMOUNTS AT ALL. WHILE IT'S POSSIBLE THAT SOME OF THESE AREAS LARGELY
MISS OUT, THE FACT THAT FORECAST SOUNDING PROFILES ARE SO FAVORABLE
FOR EFFICIENT SNOW TO LIQUID RATIOS IF SNOW DOES MANAGE TO BEAT THE
LOW LEVEL DRY AIR STILL KEEPS THE ADVISORY AREAS IN PLAY FOR LIGHT
ACCUMULATIONS ON ROADS.
MEANWHILE, AREAS FARTHER SOUTH (CENTRAL, EAST-CENTRAL, SOUTHEAST
MISSOURI AND SOUTHWEST, CENTRAL ILLINOIS) REMAIN IN LINE TO SEE
HEAVY SNOW DURING THE SECOND ROUND OVERNIGHT TONIGHT THROUGH
TOMORROW MORNING (ROUGHLY MIDNIGHT TO NOON). THERE IS LIKELY TO BE A
SHARP GRADIENT BETWEEN THESE HEAVIER ACCUMULATIONS AND THE MUCH
LIGHTER AMOUNTS TO THE NORTH, AND THERE REMAINS SOME UNCERTAINTY
REGARDING EXACTLY WHERE THIS GRADIENT WILL SET UP JUST DUE TO SLIGHT
MODEL DIFFERENCES IN THE TRACK OF THE APPROACHING SHORTWAVE. AS
SUCH, WHILE SOME OF THE NORTHERNMOST COUNTIES IN THE WINTER STORM
WARNING MAY END UP FALLING SHORT OF WARNING LEVEL AMOUNTS (5+
INCHES), CONFIDENCE REMAINS HIGH THAT A SUBSTANTIAL CORRIDOR OF
HEAVY SNOW WILL MATERIALIZE IN THE WARNING AREA. THIS IS ALSO VERY
LIKELY (70-80%) TO INCLUDE THE ST. LOUIS METRO AREA AS WELL,
ALTHOUGH WE WILL BE KEEPING A CLOSE EYE ON THAT NORTHERN GRADIENT
FOR SIGNS OF SHIFTING FARTHER TO THE SOUTH.
WITHIN THE FOOTPRINT OF HEAVIER SNOW, FINAL AMOUNTS WILL LIKELY BE
DICTATED BY A COMBINATION OF MESOSCALE FACTORS, INCLUDING VARIABLE
SNOW TO LIQUID RATIOS AND LOCALLY HIGHER PRECIPITATION RATES WITHIN
MESOSCALE BANDS. AS MENTIONED PREVIOUSLY, WARM AIR ADVECTION ALOFT
IS EXPECTED TO DRIVE SOME WARMING IN THE MID-LEVELS OF THE COLUMN IN
MANY AREAS OVERNIGHT AND TOMORROW MORNING, PARTICULARLY ALONG OUR
SOUTHEASTERN BORDER. WHILE MODEL GUIDANCE HAS BACKED OFF ENOUGH ON
THIS TO SIGNIFICANTLY REDUCE THE POTENTIAL FOR SLEET TO MIX IN, THIS
WARMING ALOFT STILL PUSHES A SIGNIFICANT PORTION OF THE CLOUD LAYER
OUTSIDE OF THE DENDRITIC GROWTH ZONE IN OUR SOUTHEASTERN AREAS, AND
LIKELY WOULD REDUCE OUR SNOW TO LIQUID RATIOS AS A RESULT.
INCREASING LIQUID EQUIVALENT AMOUNTS WILL ALMOST CERTAINLY MAKE
UP FOR SOME OF THIS, BUT THESE REDUCED SLRS MAY PREVENT SOME OF
THESE AREAS FROM QUITE REACHING THOSE UPPER END (75TH TO 90TH
PERCENTILE) AMOUNTS, ALBEIT STILL ENOUGH TO CAUSE SIGNIFICANT
IMPACTS.
HOWEVER, SOMEWHERE IN BETWEEN THAT ZONE AND THE SHARP GRADIENT ON
THE NORTHERN FLANK OF THE PRECIPITATION SHIELD IS WHERE SNOW AMOUNTS
WILL LIKELY BE MAXIMIZED, AS THIS IS WHERE MORE FAVORABLE SNOW TO
LIQUID RATIOS ARE MOST LIKELY TO OVERLAP WITH HIGHER
PRECIPITATION RATES. IN THESE AREAS, SNOWFALL RATES OF 1 TO 2
INCHES PER HOUR WILL BE ACHIEVABLE, PARTICULARLY WITHIN ANY
MESOSCALE BANDS THAT FORM, AND IT IS ALSO WHERE FINAL AMOUNTS ARE
MOST LIKELY TO REACH THE UPPER END OF THE FORECAST RANGE (9 TO 12
INCHES).
IN ANY CASE, SIGNIFICANT IMPACTS TO TRAVEL ARE EXPECTED THROUGHOUT
THIS FOOTPRINT OVERNIGHT TONIGHT THROUGH THE DAY TOMORROW. SNOW
SHOULD BEGIN WINDING DOWN BY LATE MORNING AND LARGELY END BY
SUNSET, BUT IN THE AREAS WHERE THE HEAVIEST SNOW FALLS IT WILL
TAKE TIME TO REMOVE SNOW FROM ROADS AND TRAVEL IMPACTS ARE LIKELY
TO PERSIST AS A RESULT. FORTUNATELY, MODEST WIND SPEEDS WILL
REDUCE THE POTENTIAL FOR BLOWING AND DRIFTING SNOW, BUT
REGARDLESS, SNOW WILL READILY STICK TO UNTREATED ROADS WHEREVER
IT FALLS, AND WHERE HEAVY SNOW FALLS IT WILL PERSIST UNTIL IT IS
CLEARED OR UNTIL WARMER TEMPERATURES AND/OR SUN ARRIVE.
FINALLY, ANOTHER FACTOR AT PLAY THROUGHOUT ALL OF THIS IS THE
CONTINUATION OF BITTER COLD TEMPERATURES (LOW TEENS TO SINGLE
DIGITS), WHICH WILL PREVENT SNOW FROM MELTING PRETTY MUCH EVERYWHERE
EXCEPT WHERE ROADS ARE TREATED. TEMPERATURES AND WIND CHILLS REMAIN
LIKELY TO RISE JUST ENOUGH DURING THE DAY TODAY TO ALLOW FOR OUR
ONGOING COLD WEATHER ADVISORY TO EXPIRE, BUT THIS WILL ONLY BE A
MARGINAL IMPROVEMENT, AND IT IS GOING TO REMAIN PLENTY COLD ENOUGH
TO PREVENT SNOW FROM MELTING ON ITS OWN. THEN, ONCE SNOW IS FIRMLY
IN PLACE BY SUNDAY NIGHT, EFFICIENT RADIATIVE COOLING THANKS TO THE
FRESH SNOWPACK IS LIKELY TO RESULT IN NEAR TO SLIGHT BELOW ZERO LOW
TEMPERATURES SUNDAY NIGHT AND MONDAY MORNING, WITH WIND CHILLS ONCE
AGAIN LIKELY TO FALL TO NEAR 15 BELOW ACROSS ALMOST THE ENTIRE AREA.
AS SUCH, IT'S LIKELY THAT WE WILL END UP WITH ANOTHER WIDESPREAD
COLD WEATHER ADVISORY AT THE VERY LEAST FOR SUNDAY NIGHT AND MONDAY
MORNING, ALTHOUGH THIS WILL LIKELY WAIT UNTIL AFTER OUR CURRENT COLD
WEATHER HEADLINES EXPIRE LATER THIS AFTERNOON.
BRC
LONG TERM
(SUNDAY NIGHT THROUGH FRIDAY)
ISSUED AT 349 AM CST SAT JAN 24 2026
AFTER THIS WEEKEND'S EVENT, THE PRIMARY IMPACT FOR THE REST OF THE
WEEK WILL BE THE CONTINUATION OF COLD TEMPERATURES, WHICH WILL ONLY
BE BRIEFLY INTERRUPTED BY MODERATING TEMPERATURES TUESDAY AND
WEDNESDAY AFTERNOONS, WHEN WE MAY APPROACH THE FREEZING MARK IN SOME
AREAS, ALTHOUGH EVEN THIS MAY BE A STRETCH WHEREVER WE HAVE A DEEP
SNOWPACK. THEN, NORTHWEST FLOW WILL DRIVE ANOTHER COLD FRONT THROUGH
THE AREA, AND KEEP TEMPERATURES SUPPRESSED AND LIKELY BELOW FREEZING
THROUGH THE END OF THE WEEK. WHILE WE'LL LIKELY SEE JUST ENOUGH
WARMING AND SUN THROUGHOUT THE WEEK DURING THE DAY TO HELP WITH SNOW
ON THE ROADS, WE ARE LIKELY TO HANG ON TO SNOW COVER THROUGHOUT THE
WEEK WHERE THE HEAVIEST SNOW FALLS. MEANWHILE, MORNING LOWS ARE
LIKELY TO REMAIN IN THE TEENS AND SINGLE DIGITS THROUGHOUT THIS
PERIOD. PRECIPITATION CHANCES REMAIN LOW AFTER SUNDAY AFTERNOON,
ALTHOUGH THERE ARE HINTS OF A WEAK CLIPPER AND SOME LIGHT SNOW
AROUND MID-WEEK.
BRC
AVIATION
(FOR THE 12Z TAFS THROUGH 12Z SUNDAY MORNING)
ISSUED AT 445 AM CST SAT JAN 24 2026
A SIGNIFICANT WINTER STORM WILL IMPACT ALL LOCAL TERMINALS TO
VARYING DEGREES THIS TAF CYCLE DUE TO ACCUMULATING SNOWFALL.
WIDESPREAD AND MOSTLY LIGHT ACCUMULATING SNOW IS EXPECTED TO
IMPACT ALL TERMINALS BEGINNING EARLY THIS MORNING AT COU/JEF, AND
SPREAD TO TERMINALS IN THE AFTERNOON. THIS INITIAL ROUND WILL BE
MOSTLY LIGHT, BUT WILL READILY ACCUMULATE ON UNTREATED PAVEMENT
DUE TO EXPECTED COLD TEMPERATURES. VISIBILITY REDUCTIONS ARE ALSO
LIKELY, ALONG WITH CEILING REDUCTIONS TO MVFR LEVELS.
SNOW RATES MAY REDUCE THIS EVENING AND OVERNIGHT, ESPECIALLY AT
UIN. HOWEVER, ANOTHER ROUND OF SNOW IS EXPECTED FROM ROUGHLY 06Z
ONWARD TOMORROW, BRINGING THE POTENTIAL FOR HEAVIER ACCUMULATIONS.
THE MOST SIGNIFICANT ACCUMULATIONS AND VISIBILITY REDUCTIONS ARE
EXPECTED AT ST. LOUIS AREA TERMINALS (STL/SUS/CPS), WITH
IMPACTS ALSO LIKELY AT COU/JEF. UIN IS LESS LIKELY TO SEE IMPACTS
FROM THIS SECOND ROUND, BUT SOME LIGHT ADDITIONAL SNOW IS
POSSIBLE HERE TOO.
BRC
LSX WATCHES/WARNINGS/ADVISORIES
MO...COLD WEATHER ADVISORY UNTIL NOON CST TODAY 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.
WINTER STORM WARNING FROM 9 AM THIS MORNING TO 6 PM CST SUNDAY
FOR AUDRAIN MO-LINCOLN MO-PIKE MO-RALLS MO.
WINTER STORM WARNING UNTIL 6 PM CST SUNDAY FOR BOONE MO-CALLAWAY
MO-COLE MO-CRAWFORD MO-FRANKLIN MO-GASCONADE MO-IRON MO-
JEFFERSON MO-MADISON MO-MONITEAU MO-MONTGOMERY MO-OSAGE MO-
REYNOLDS MO-SAINT CHARLES MO-SAINT FRANCOIS MO-SAINT LOUIS
CITY MO-SAINT LOUIS MO-SAINTE GENEVIEVE MO-WARREN MO-
WASHINGTON MO.
WINTER WEATHER ADVISORY FROM 9 AM THIS MORNING TO 6 PM CST
SUNDAY FOR KNOX MO-LEWIS MO-MARION MO-MONROE MO-SHELBY MO.
IL...COLD WEATHER ADVISORY UNTIL NOON CST TODAY 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.
WINTER STORM WARNING FROM 9 AM THIS MORNING TO 6 PM CST SUNDAY
FOR CALHOUN IL-GREENE IL-JERSEY IL-MACOUPIN IL-MONTGOMERY
IL-PIKE IL.
WINTER STORM WARNING UNTIL 6 PM CST SUNDAY FOR BOND IL-CLINTON
IL-FAYETTE IL-MADISON IL-MARION IL-MONROE IL-RANDOLPH IL-
SAINT CLAIR IL-WASHINGTON IL.
WINTER WEATHER ADVISORY FROM 9 AM THIS MORNING TO 6 PM CST
SUNDAY FOR ADAMS IL-BROWN IL.
WFO LSX
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