977
FXUS63 KLSX 011049
AFDLSX
AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE SAINT LOUIS MO
549 AM CDT TUE APR 1 2025
KEY MESSAGES
- STRONG TO SEVERE THUNDERSTORMS ARE POSSIBLE AFTER MIDNIGHT
TONIGHT, PRIMARILY ACROSS PARTS OF CENTRAL AND NORTHEAST
MISSOURI. SEVERE THUNDERSTORMS ARE MORE LIKELY ON WEDNESDAY
AFTERNOON.
- PERIODS OF HEAVY RAIN ARE LIKELY THURSDAY THROUGH SATURDAY. THE
THREAT OF RIVER FLOODING IS BECOMING MORE LIKELY ACROSS PARTS OF
SOUTHEAST MISSOURI AND SOUTHERN ILLINOIS. FLASH FLOODING WILL
WILL ALSO BE POSSIBLE IN THESE AREAS.
SHORT TERM
(THROUGH LATE WEDNESDAY AFTERNOON)
ISSUED AT 425 AM CDT TUE APR 1 2025
A RIDGE OF HIGH PRESSURE HAS MOVED EAST OF THE FORECAST AREA THIS
MORNING, AND THE WIND HAS TURNED BACK TO THE EAST-SOUTHEAST. WINDS
WILL CONTINUE TO VEER TO THE SOUTHEAST AND BECOME INCREASE AS THE
PRESSURE GRADIENT TIGHTENS BETWEEN THE HIGH TO OUR EAST AND A
STRENGTHENING LOW PRESSURE SYSTEM OVER THE CENTRAL PLAINS. THE
SOUTHEAST FLOW WILL BOOST TEMPERATURES BACK INTO THE UPPER 50S TO
MID 60S THIS AFTERNOON.
THE LOW LEVEL JET INCREASES THIS EVENING AS THE LOW OVER THE PLAINS
CONTINUES TO DEEPEN AND MOVE EAST. ALL GUIDANCE SHOWS MODERATE TO
STRONG MOISTURE CONVERGENCE ACROSS MISSOURI AND ILLINOIS DURING THE
EVENING. HOWEVER ONLY THE GFS OF THE OPERATIONAL DETERMINISTIC
MODELS SPITS OUT A SIGNIFICANT AMOUNT OF QPF DURING THE EVENING. A
FEW OF THE CAMS DEVELOP SPOTTY SHOWERS AS WELL, MOSTLY OVER CENTRAL
AND NORTHEAST MISSOURI INTO WEST CENTRAL ILLINOIS. WITH MOST MODELS
STAYING DRY THROUGH THE EVENING, HAVE LOWERED POPS TO CHANCE BEFORE
MIDNIGHT. THE REAL CHANCE FOR PRECIP DEVELOPS OVERNIGHT INTO
WEDNESDAY MORNING. CONVECTION IS EXPECTED TO DEVELOP OVER THE
EASTERN PLAINS DURING THE EVENING ON THE NOSE OF THE LOW LEVEL JET
WHICH WILL BE SCREAMING AT 60-70KTS JUST AHEAD OF THE LOW. CAMS
SHOW THE STORMS GROWING UPSCALE INTO MULTIPLE LINES AS THEY MOVE
EAST THROUGH THE NIGHT. THERE ARE TIMING DIFFERENCES IN WHEN THE
STORMS REACH OUR AREA, BUT THE CONSENSUS IS SOMETIME BETWEEN 08-12Z
WEDNESDAY. LEANED TOWARD THE EARLIER SOLUTIONS AS THE MODELS CAN BE
A LITTLE SLOW IN THESE SITUATIONS. FORECAST SOUNDINGS SHOW A VERY
PRONOUNCED LOW LEVEL INVERSION, SO THE STORMS SHOULD BE ELEVATED BY
THE TIME THEY REACH OUR AREA. GIVEN THAT, LARGE HAIL SHOULD BE THE
PRIMARY SEVERE WEATHER THREAT WITH 1000-1500 J/KG OF MUCAPE AND
SHEAR IN THE 50-60KT RANGE. THE LOW LEVEL WIND FIELD WILL BE VERY
STRONG, WITH UP TO 60KTS ONLY 2500 FEET ABOVE THE GROUND, SO AN
ISOLATED DAMAGING WIND GUST WILL BE POSSIBLE AS WELL IF A STRONGER
STORM CAN MIX THAT DOWN THROUGH THE INVERSION.
THERE ARE STILL A LOT OF UNCERTAINTY IN THE SEVERE FORECAST FOR
WEDNESDAY. MORNING CONVECTION WILL CONTINUE EAST THROUGH THE DAY,
FED BY THE LOW LEVEL JET WHICH WILL CONTINUE TO RIP ALONG AT 50-60TS
UNTIL THE LOW BEGINS ACCELERATING NORTHEAST DURING THE LATE
AFTERNOON. THE CLOUDS AND SHOWERS COULD REALLY LIMIT INSTABILITY,
THEREBY LIMITING THE STRENGTH OF AFTERNOON CONVECTION. SEVERAL CAMS
SEEM TO SHOW THIS WITH WEAKER AFTERNOON CONVECTION THAN OTHERS. MOST
NOTABLY THOUGH, THE GFS AND RAP SHOW A NARROW CORRIDOR OF RECOVERING
INSTABILITY DURING THE AFTERNOON JUST AHEAD OF THE FRONT IN A
VIRTUALLY UNCAPPED ATMOSPHERE. BY 21-22Z MLCAPE HITS 1400-1800 J/KG
AND SBCAPE HITS 1800-2200 J/KG. IF ANYTHING THE SHEAR WILL BE
STRONGER DURING THE AFTERNOON THAN IT WAS IN THE MORNING. THIS
ENVIRONMENT WOULD PROMOTE ROTATING UPDRAFTS THEREFORE DAMAGING
WINDS, VERY LARGE HAIL AND TORNADOES WOULD ALL BE POSSIBLE. THE
MODE STILL LOOKS MESSY SINCE THE SHEAR IS NEARLY PARALLEL TO THE
BOUNDARY, BUT LINES/CLUSTERS OF SUPERCELLS AND MERGERS LOOK LIKELY
IF THE INSTABILITY CAN BE REALIZED WEDNESDAY AFTERNOON. THE FRONT
WILL SLOWING DOWN WEDNESDAY AFTERNOON AS THE LOW DRIVING IT MOVES
NORTHEAST AWAY FROM US. TIMING THE END OF THE THUNDERSTORM THREAT
IN OUR EASTERN AND SOUTHERN COUNTIES IS THEREFORE DIFFICULT. MOST
GUIDANCE HAS IT ENDING IN SOUTHEAST MISSOURI AND SOUTH CENTRAL
ILLINOIS BETWEEN 00-03Z.
ONE LAST HAZARD TO MENTION BEFORE MOVING BEYOND WEDNESDAY. GRADIENT
WINDS WILL BE VERY STRONG ON WEDNESDAY DUE TO THE TIGHT PRESSURE
GRADIENT BETWEEN THE LOW WHICH WILL BE MOVING INTO THE UPPER MIDWEST
AND THE RIDGE OF HIGH PRESSURE OVER THE EASTERN U.S. CURRENT
FORECAST IS FOR SUSTAINED WINDS OF 20-25KTS WITH GUSTS TO 40+ KTS
UNTIL THE GRADIENT SLACKENS DURING THE LATE AFTERNOON AND EVENING.
CARNEY
LONG TERM
(WEDNESDAY NIGHT THROUGH MONDAY)
ISSUED AT 425 AM CDT TUE APR 1 2025
THE REMAINDER OF THE WEEK LOOKS NO LESS BUSY THAN WEDNESDAY, THOUGH
FOR DIFFERENT REASONS. THE COLD FRONT STALLS OVER ARKANSAS/WEST
TENNESSEE WEDNESDAY NIGHT, WHERE IT STAYS UNTIL SATURDAY NIGHT. A
LARGE TROUGH OVER THE DESERT SOUTHWEST EJECTS SEVERAL WAVES OF
VORTICITY WHICH RIPPLE OVER THE FRONT THURSDAY THROUGH SATURDAY,
INCREASING THE SYNOPTIC SCALE LIFT. ALL THE WHILE A STRONG PRESSURE
GRADIENT BETWEEN THE TROUGH TO THE WEST AND HIGH PRESSURE OVER THE
WESTERN ATLANTIC AND GULF WILL KEEP THE LOW LEVEL JET POINTED RIGHT
AT THE BAROCLINIC ZONE OVER NORTHERN ARKANSAS AND SOUTHERN MISSOURI.
DETERMINISTIC GUIDANCE SHOWS WAVES OF VERY STRONG MOISTURE
CONVERGENCE MOVING ACROSS NORTHERN ARKANSAS AND SOUTHERN MISSOURI
THURSDAY THROUGH SATURDAY WHICH WILL PRODUCE PERIODS OF HEAVY RAIN.
NAEFS P-WAT FORECASTS ARE SHOWING 1.50+ INCHES AT TIMES WHICH IS IN
THE 99.9TH TO MAX CLIMATOLOGICAL PERCENTILE FOR EARLY APRIL. TIMING
THE WAVES OF HEAVIEST PRECIP IS TOUGH AS THE MODELS NEVER REALLY
STOP PRECIPITATING AND ARE CONSTANTLY CONTAMINATED WITH CONVECTIVE
FEEDBACK. THE LATEST QPF FROM WPC FOR WEDNESDAY THROUGH EARLY SUNDAY
MORNING RANGES FROM AROUND 2 INCHES IN NORTHEAST MISSOURI TO 9+ IN
SOUTHEAST MISSOURI WITH AS 8+ IN SOUTHWEST AND SOUTH CENTRAL
ILLINOIS. IF THESE AMOUNTS ARE REALIZED, RIVER FLOODING IS A
VIRTUAL CERTAINTY ACROSS THE EASTERN OZARKS INTO SOUTHERN ILLINOIS
AND FLASH FLOODING IS A REAL POSSIBILITY. ADDITIONALLY, THE ECMWF
ENSEMBLE EXTREME FORECAST INDEX QPF HIGHLIGHTS MUCH OF SOUTHEAST
MISSOURI FRIDAY NIGHT WITH ABNORMALLY HIGH QPF, AND THE SHIFT OF
TAILS IS +2 INDICATING THE THERE'S SOME PROBABILITY THAT SOME
MEMBERS OF THE ENSEMBLE ARE FORECASTING QPF GREATER THAN THE 99TH
CLIMATE PERCENTILE, WHICH ADDS CONFIDENCE THAT THIS COULD BE AN
EXTREME EVENT.
THE HEAVY RAIN THREAT ENDS SUNDAY AS THE LONG WAVE TROUGH MOVES EAST
INTO THE PLAINS AND MIDWEST. ASIDE FROM A CHANCE OF LINGERING LIGHT
RAIN SUNDAY, THE REMAINDER OF THE FORECAST LOOKS DRY. THE DEEP
TROUGH DRAGS A COLD HIGH INTO THE MISSISSIPPI VALLEY SUNDAY NIGHT
INTO MONDAY, WHICH HAS THE POTENTIAL TO DROP TEMPERATURES BELOW
FREEZING MONDAY AND TUESDAY MORNING.
CARNEY
AVIATION
(FOR THE 12Z TAFS THROUGH 12Z WEDNESDAY MORNING)
ISSUED AT 544 AM CDT TUE APR 1 2025
WINDS WILL INCREASE FROM THE SOUTHEAST AND BECOME GUSTY TODAY.
WIND GUSTS OF 20-30KTS ARE LIKELY BY 00Z AND WILL CONTINUE THROUGH
THE NIGHT. IF GUSTS CEASE AT ANY TIME TONIGHT, LOW LEVEL WIND
SHEAR WILL BECOME A PROBLEM ACROSS THE AREA, HOWEVER GUIDANCE
SUGGESTS THAT GUSTS WILL PERSIST ALL NIGHT. OTHERWISE, VFR FLIGHT
CONDITIONS ARE EXPECTED TO PREVAIL UNTIL AFTER 06Z WHEN CEILINGS
ARE LIKELY TO FALL TO MVFR AS AN AREA OF SHOWERS AND THUNDERSTORMS
MOVES IN FROM THE WEST.
VFR FLIGHT CONDITIONS ARE EXPECTED THROUGH THE
CARNEY
LSX WATCHES/WARNINGS/ADVISORIES
MO...NONE.
IL...NONE.
WFO LSX
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