764
FXUS63 KLSX 270945
AFDLSX
AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE SAINT LOUIS MO
345 AM CST FRI FEB 27 2026
KEY MESSAGES
- GUSTY SOUTHWEST WINDS, LOW HUMIDITY, AND VERY DRY VEGETATION
WILL CREATE DANGEROUS OUTDOOR BURNING CONDITIONS IN MUCH OF THE
AREA TODAY, AND A RED FLAG WARNING HAS BEEN ISSUED FOR THESE
AREAS.
- CONFIDENCE REMAINS HIGH (80%) THAT AT LEAST LIGHT (BUT
IMPACTFUL) WINTRY PRECIPITATION ACCUMULATIONS WILL OCCUR SUNDAY
EVENING THROUGH MONDAY MORNING, WITH BEST CHANCES REMAINING
ALONG AND NORTH OF I-70.
- A PROLONGED ACTIVE PATTERN REMAINS LIKELY NEXT WEEK, WITH
MULTIPLE OPPORTUNITIES FOR WIDESPREAD RAINFALL AND POSSIBLY
THUNDERSTORMS AS WELL.
SHORT TERM
(THROUGH LATE SATURDAY AFTERNOON)
ISSUED AT 310 AM CST FRI FEB 27 2026
AN ACTIVE WEEK OF WEATHER IS ON TAP FOR OUR AREA, WITH SEVERAL
POTENTIAL HAZARDS AND ITEMS OF INTEREST TO DISCUSS...RANGING FROM
FIRE WEATHER TOMORROW, TO WINTER WEATHER LATE SUNDAY / EARLY
MONDAY, TO WIDESPREAD RAINFALL AND POSSIBLY THUNDERSTORMS FROM
LATE MONDAY THROUGH MID WEEK (AND BEYOND). QUITE A SMORGASBORD,
TO BE SURE.
THE FIRST ITEM ON THE AGENDA IS THE POTENTIAL FOR CRITICAL FIRE
WEATHER CONDITIONS THIS AFTERNOON, THANKS TO GUSTY SOUTHWESTERLY
WINDS, LOW HUMIDITY, AND VERY DRY VEGETATION. DURING THE DAY TODAY,
A TIGHTENING PRESSURE GRADIENT AHEAD OF AN APPROACHING WEAK COLD
FRONT IS EXPECTED TO DRIVE BREEZY SOUTHWEST WINDS, WHICH WILL BE
AIDED BY FULL SUN AND DEEP MIXING TO NEARLY 800 MB. WHILE WIND
SPEEDS ALOFT DO NOT APPEAR TO BE PARTICULARLY EXTREME, CONFIDENCE IS
HIGH THAT THIS DEEP MIXING SHOULD ALLOW FOR SURFACE GUSTS TO REACH
THE 30 TO 35 MPH RANGE, WHICH IS NEAR THE 75TH-90TH PERCENTILES FOR
HREF GUST SPEEDS. MEANWHILE, THIS DEEP MIXING, COMBINED WITH ROBUST
WARM AIR ADVECTION, SHOULD RESULT IN MINIMUM RELATIVE HUMIDITY
VALUES OF NEAR AND BELOW 30% IN MOST OF THE AREA (NOT TO MENTION
AFTERNOON TEMPERATURES 20 TO 25 DEGREES ABOVE AVERAGE), WITH A
RELATIVELY LARGE FOOTPRINT OF SUB-25% RH VALUES AS WELL. NOT TO
MENTION, VEGETATION REMAINS VERY DRY THROUGHOUT THE AREA, BOTH DUE
TO THE TYPICAL SEASONAL CURING AND ALSO A GENERAL LACK OF
SIGNIFICANT RECENT RAINFALL.
AS SUCH, CONFIDENCE IS HIGH THAT SEVERAL HOURS OF CRITICAL FIRE
WEATHER CONDITIONS WILL BE ACHIEVED, AND WE HAVE BOTH UPGRADED THE
ONGOING FIRE WEATHER WATCH TO A RED FLAG WARNING, AND EXPANDED ITS
FOOTPRINT SOUTHWARD TO COVER MOST OF CENTRAL MISSOURI AND EVEN PARTS
OF THE ST. LOUIS METRO AREA. THIS ROUGHLY ALIGNS WITH THE HREF 75TH
PERCENTILE FOOTPRINT OF 15 MPH SUSTAINED WINDS, WHICH SHOULD BE
ACHIEVABLE THANKS TO THE EXPECTED DEEP MIXING. FARTHER SOUTH,
"ELEVATED" CONDITIONS WILL LIKELY BE MORE COMMON DUE TO THE SLIGHTLY
LOWER EXPECTED WINDS, BUT THIS WILL NEED TO BE MONITORED EVEN HERE.
TOMORROW EVENING, WIND SPEEDS ARE EXPECTED TO WEAKEN QUICKLY, AND
OVERNIGHT A WEAK COLD FRONT IS EXPECTED TO SINK INTO THE AREA AND
STALL, AND IT WILL REMAIN DRAPED ACROSS THE AREA THROUGH THE DAY
SATURDAY. MEANWHILE, A SUBTLE SHORTWAVE AND ATTENDANT SURFACE LOW IS
EXPECTED TO TRAVERSE THIS STALLED BOUNDARY DURING THE AFTERNOON,
BRINGING SOME MODEST MID-LEVEL MOISTURE AND LIFT THAT COULD SQUEEZE
OUT A FEW LIGHT SHOWERS DURING THE DAY. CONSIDERING THAT THE LOW
LEVELS WILL BE VERY DRY AS THIS OCCURS, WE DON'T EXPECT THIS TO
AMOUNT TO MUCH MORE THAN A FEW POCKETS OF SHOWERS AND A LOT OF
VIRGA. IN FACT, WHILE SURFACE WINDS ARE EXPECTED TO BE WEAKER THAN
FRIDAY OVERALL, IT'S NOT ENTIRELY OUT OF THE QUESTION THAT A FEW
AREAS COULD SEE BRIEF PERIODS OF ELEVATED FIRE WEATHER CONDITIONS
AGAIN SATURDAY (RH 30-35%, SUSTAINED SURFACE WINDS 10-15 MPH). THIS
CURRENTLY APPEARS TO BE A LIMITED THREAT, BUT SOMETHING TO KEEP AN
EYE ON. MEANWHILE, THE PRESENCE OF THE STALLED COLD FRONT DOES
COMPLICATE THE TEMPERATURE FORECAST A BIT, AS AREAS NORTH OF THE
BOUNDARY ARE LIKELY TO SEE SOME NOTABLE COOLING WHILE AREAS TO THE
SOUTH ONCE AGAIN CLIMB INTO THE UPPER 60S TO LOW 70S. EXACTLY WHERE
THIS BOUNDARY STALLS WILL DETERMINE EXACTLY HOW THOSE TEMPERATURES
WILL BE DISTRIBUTED.
BRC
LONG TERM
(SATURDAY NIGHT THROUGH THURSDAY)
ISSUED AT 310 AM CST FRI FEB 27 2026
THERE ARE TWO MAIN ITEMS TO DISCUSS DURING THE EXTENDED FORECAST
PERIOD (SUNDAY - WEDNESDAY): THE FIRST IS THE POTENTIAL FOR
IMPACTFUL FROZEN PRECIPITATION ACCUMULATIONS BETWEEN LATE SUNDAY AND
EARLY MONDAY, WHICH WILL BE FOLLOWED BY WHAT APPEARS TO BE MULTIPLE
OPPORTUNITIES FOR WIDESPREAD RAINFALL AND POSSIBLY THUNDERSTORMS
MONDAY THROUGH MID-WEEK (AND LIKELY BEYOND).
WINTRY PRECIPITATION SUN/MON:
BY SATURDAY EVENING, A REINFORCING SHOT OF COLD AIR ADVECTION WILL
OCCUR AS A SHORTWAVE PASSES THROUGH THE MID AND UPPER MISSISSIPPI
RIVER VALLEY AND GREAT LAKES. THIS WILL DRIVE THE STALLED FRONT
SOUTHWARD AND USHER IN A MUCH COOLER AIRMASS SUNDAY, WITH PERHAPS A
20 TO 25 DEGREE TEMPERATURE DROP IN MOST AREAS FROM THE DAY BEFORE.
WHILE INITIALLY SUNDAY AFTERNOON THE MAIN IMPLICATION WILL BE SIMPLY
THE ABRUPT END OF SPRING-LIKE WARMTH, THIS COLDER AIRMASS WILL SET
THE STAGE FOR POTENTIAL WINTRY PRECIPITATION SUNDAY EVENING THROUGH
EARLY MONDAY. DURING THIS PERIOD, ANOTHER SHORTWAVE IS EXPECTED TO
MOVE THROUGH THE AREA, DRIVEN BY A SOUTHERN STREAM JET STREAK THAT
WILL BEGIN TO MERGE WITH THE POLAR JET ACROSS OUR AREA. WHILE THE
SHORTWAVE ITSELF IS A FAIRLY SMALL-SCALE FEATURE, THE UPPER LEVEL
DYNAMICS INVOLVED WITH THIS SETUP ARE RATHER COMPLEX, AND AS A
RESULT, DETERMINISTIC MODELS DISPLAY A RATHER IRREGULAR FORCING
PROFILE ACROSS THE AREA. WHEN COMBINED WITH OUR LOCATION NEAR THE
LOW LEVEL BAROCLINIC ZONE, OUR CONFIDENCE IN BOTH THE COVERAGE OF
FROZEN PRECIPITATION AND PRECIPITATION TYPES IS BELOW AVERAGE. TO
MAKE MATTERS WORSE, CLUSTER ANALYSIS DISPLAYS A WIDE RANGE OF
POSSIBLE PRECIPITATION DISTRIBUTIONS, BUT WITH LITTLE IN THE
SYNOPTIC FLOW PATTERN TO DISTINGUISH THESE CLUSTERS DUE TO THE
SMALL SCALE OF THE PRIMARY FORCING MECHANISM (THE AFOREMENTIONED
SHORTWAVE). IN OTHER WORDS, WHILE WE STILL EXPECT SOME LIGHT
WINTRY PRECIPITATION ACCUMULATIONS IN PARTS OF OUR AREA SUNDAY
EVENING THROUGH MONDAY MORNING, EXACTLY HOW MUCH FALLS AND WHERE
IS STILL SOMEWHAT UNCERTAIN.
HOWEVER, IT ALSO APPEARS THAT ONE TREND ESTABLISHED IN THE PREVIOUS
FORECAST CONTINUES, AND THAT IS A SLIGHT REDUCTION IN THE POTENTIAL
SNOW AMOUNTS. THIS APPEARS TO BE LARGELY DRIVEN BY AN OVERALL
REDUCTION IN MODEL QPF, AND MAY BE THE RESULT OF LOW-LEVEL DRY AIR
THAT WILL BE IN PLACE AT THE ONSET OF THE EVENT. ON THE OTHER HAND,
THIS LOW LEVEL DRY AIR MAY ALSO LEAD TO WET-BULB COOLING, AND MAY
ASSIST IN THE TRANSITION FROM RAIN TO SNOW. IT SHOULD ALSO BE
MENTIONED THAT WHILE THE ENSEMBLE MEDIAN/MEAN SNOW AMOUNTS HAVE
REDUCED SLIGHTLY IN LATEST FORECASTS, AMOUNTS REMAIN HIGH ENOUGH TO
PRODUCE TRAVEL IMPACTS, PARTICULARLY IF ANY LOCALLY HEAVIER BANDS
CAN DEVELOP AND PRODUCE HIGHER RATES. 75TH TO 90TH PERCENTILE SNOW
AMOUNTS REMAIN RELATIVELY HIGH (3 TO 5"), SO THIS POSSIBILITY CAN'T
BE DISCOUNTED. THERE HAS ALSO BEEN A CONTINUED SHIFT AWAY FROM THE
POTENTIAL FOR FREEZING RAIN, WITH SNOW THE FAVORED FROZEN
PRECIPITATION TYPE FOLLOWED BY SLEET. WHILE SOME FREEZING RAIN CAN'T
BE DISCOUNTED YET, THERE IS NOT MUCH SUPPORT IN MODEL PROFILES FOR
THIS AS OF NOW, WITH A LACK OF A DEEP WARM NOSE ALOFT.
FINALLY, THE OTHER FACTOR AT PLAY HERE WILL BE ROAD SURFACE
TEMPERATURES, WHICH MAY STILL BE RATHER WARM AS FROZEN PRECIPITATION
BEGINS TO FALL. AS SUCH, IT'S POSSIBLE THAT IMPACTFUL ACCUMULATIONS
ARE LIMITED ONLY TO NARROW SNOW/SLEET BANDS WHERE HIGHER RATES CAN
OVERCOME MELTING ON SURFACES, WHICH WOULD LIMIT THE OVERALL SCOPE OF
IMPACTS. IN ANY CASE, THE GREATEST POTENTIAL FOR THIS TO OCCUR
REMAINS FROM ROUGHLY THE I-70 CORRIDOR NORTHWARD, WITH LOW
CONFIDENCE REGARDING EXACTLY WHERE THOSE LOCALLY ENHANCED IMPACTS
WILL OCCUR.
RAINFALL NEXT WEEK:
WHILE THERE WILL BE A BRIEF LULL IN PRECIPITATION AFTER
SUNDAY/MONDAY'S WINTER EVENT, ENSEMBLE GUIDANCE CONTINUES TO SUGGEST
THAT THE UPPER FLOW PATTERN WILL TRANSITION FROM ZONAL TO
SOUTHWESTERLY FROM EARLY TO MID WEEK, AND REMAIN SOUTHWESTERLY
POTENTIALLY THROUGH THE END OF THE WEEK (OR LONGER). THIS PLACES
OUR AREA WITHIN AN ACTIVE STORM TRACK, AND ALSO ALLOWS FOR
PERSISTENT MOISTURE ADVECTION. ENSEMBLE MEAN PRECIPITABLE WATER
VALUES IN BOTH THE NAEFS AND ECMWF REACH OR EXCEED THE 90TH
PERCENTILE BY TUESDAY AND REMAIN THERE THROUGH THE END OF THE
WEEK, WITH MULTIPLE POTENTIAL SHORTWAVES MOVING THROUGH THE AREA
FROM WEDNESDAY ONWARD. NOT SURPRISINGLY, ENSEMBLE GUIDANCE
CONTINUES TO DEPICT MULTIPLE ROUNDS OF WIDESPREAD AND SUBSTANTIAL
RAINFALL THROUGHOUT THE EXTENDED PERIOD, AND THIS APPEARS TO BE
RATHER REASONABLE CONSIDERING THE LARGE SCALE PATTERN AT HAND.
CONFIDENCE IN THE CEILING OF THIS RAINFALL AND THE POTENTIAL
IMPACTS REMAINS LOW, BUT WE DO EXPECT A RETURN TO AN ACTIVE AND
WET PATTERN OVERALL. MEANWHILE, THERE IS ALSO THE POTENTIAL FOR
THE RETURN OF THUNDERSTORMS DURING THIS PERIOD, PARTICULARLY BY
WEDNESDAY, PENDING THE DEGREE OF INSTABILITY THAT IS REALIZED.
THESE DETAILS WILL NEED TO BE IRONED OUT IN THE COMING DAYS.
BRC
AVIATION
(FOR THE 12Z TAFS THROUGH 12Z SATURDAY MORNING)
ISSUED AT 341 AM CST FRI FEB 27 2026
VFR CONDITIONS ARE EXPECTED THROUGHOUT THE 12Z TAF PERIOD, AND
WINDS WILL BE THE PRIMARY FOCUS. WHILE WINDS WILL BE LIGHT AT THE
START OF THE PERIOD, BREEZY SOUTHWESTERLY WINDS WILL DEVELOP BY
LATE MORNING AND PERSIST THROUGH LATE AFTERNOON. WIND SPEEDS WILL
DIMINISH QUICKLY JUST PRIOR TO SUNSET, AND A WEAK COLD FRONT WILL
SINK INTO THE AREA. AS A RESULT, LIGHT WINDS WITH A VARIABLE
DIRECTION ARE EXPECTED OVERNIGHT THROUGH EARLY TOMORROW MORNING.
NO PRECIPITATION IS EXPECTED, AND SKIES ARE EXPECTED TO REMAIN
MOSTLY CLEAR.
BRC
LSX WATCHES/WARNINGS/ADVISORIES
MO...RED FLAG WARNING FROM NOON TODAY TO 6 PM CST THIS EVENING FOR
AUDRAIN MO-BOONE MO-CALLAWAY MO-COLE MO-FRANKLIN MO-
GASCONADE MO-KNOX MO-LEWIS MO-LINCOLN MO-MARION MO-MONITEAU
MO-MONROE MO-MONTGOMERY MO-OSAGE MO-PIKE MO-RALLS MO-SAINT
CHARLES MO-SAINT LOUIS CITY MO-SAINT LOUIS MO-SHELBY MO-
WARREN MO.
IL...RED FLAG WARNING FROM NOON TODAY TO 6 PM CST THIS EVENING FOR
ADAMS IL-BROWN IL-CALHOUN IL-GREENE IL-JERSEY IL-MACOUPIN
IL-MADISON IL-PIKE IL.
WFO LSX
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