538
FXUS63 KLSX 311647
AFDLSX
AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE SAINT LOUIS MO
1147 AM CDT MON MAR 31 2025
KEY MESSAGES
- STRONG TO SEVERE THUNDERSTORMS ARE POSSIBLE AGAIN TUESDAY NIGHT,
AND SEVERE THUNDERSTORMS LOOK LIKELY ON WEDNESDAY.
- PERIODS OF HEAVY RAIN ARE LIKELY THURSDAY THROUGH SATURDAY,
MAINLY ACROSS SOUTHEAST MISSOURI INTO SOUTHWEST ILLINOIS. THESE
PERIODS OF HEAVY RAIN MAY CAUSE RIVER FLOODING AND FLASH
FLOODING.
SHORT TERM
(THROUGH LATE TUESDAY AFTERNOON)
ISSUED AT 344 AM CDT MON MAR 31 2025
A RIDGE OF HIGH PRESSURE OVER GREAT PLAINS WILL MOVE EAST TODAY AND
TONIGHT AND WILL BE OVER THE OHIO VALLEY AND GREAT LAKES REGION BY
12Z TUESDAY MORNING. NORTHWEST FLOW TODAY ON THE EASTERN SIDE OF
THE RIDGE AXIS WILL BRING COOLER AND DRIER AIR TO THE MISSISSIPPI
VALLEY. FORECAST SOUNDINGS SHOW COLD ADVECTION STRATO-CU HANGING
AROUND THROUGH MOST OF THE MORNING, BUT SCATTERING OUT BY EARLY TO
MID AFTERNOON. BETWEEN THE LOW CLOUDS AND COLD NORTHWEST FLOW,
HIGHS WILL AS MUCH AS 20 DEGREES LOWER THAN SUNDAY'S FOR MOST OF
EASTERN MISSOURI AND SOUTHWEST/SOUTH CENTRAL ILLINOIS.
WINDS BECOME LIGHT AND VARIABLE TONIGHT AS THE RIDGE TRANSITS THE
MISSISSIPPI VALLEY. LIGHT WINDS AND A CLEAR SKY SHOULD PRODUCE
EXCELLENT RADIATIONAL COOLING CONDITIONS. WITH THAT IN MIND, AM
LEANING ON THE COLD SIDE OF GUIDANCE WITH TEMPERATURES MAINLY IN THE
MID 30S, BUT SOME OF OUR COLDER SPOTS WILL LIKELY APPROACH OR FALL A
DEGREE OR TWO BELOW FREEZING. AT LEAST SOME PATCHY OR AREAS OF
FROST WILL BE POSSIBLE, PARTICULARLY ACROSS SOUTH CENTRAL ILLINOIS
WHERE THE WIND WILL BE LIGHT AND VARIABLE THE LONGEST DURING THE
COLDEST PART OF THE NIGHT. GUIDANCE SHOWS HIGH CLOUDS MOVING INTO
AREAS FARTHER WEST AFTER MIDNIGHT, SO FROST MAY NOT BE AS MUCH OF A
PROBLEM.
SOUTHERLY FLOW RETURNS TUESDAY WITH THE RIDGE AXIS EAST OF THE
MISSISSIPPI VALLEY. THE NEXT UPSTREAM MID/UPPER LEVEL TROUGH WILL
BE MOVING CROSS THE ROCKIES INTO THE GREAT PLAINS, WHICH WILL FORCE
CYCLOGENESIS OVER THE CENTRAL PLAINS RESULTING IN A STRENGTHENING
PRESSURE GRADIENT BETWEEN THE RIDGE OVER THE OHIO VALLEY AND THE
DEEPENING LOW OVER THE PLAINS. THIS WILL TRANSLATE TO ANOTHER
BREEZY DAY. FORECAST SOUNDINGS SHOW THE ATMOSPHERE MIXING UP TO
BETWEEN 900-850MB TUESDAY AFTERNOON WHERE WIND SPEEDS ARE FORECAST
TO BE IN THE 30-40KT RANGE. GIVEN HOW THE NBM HAS BEEN
UNDER-FORECASTING WINDS/GUSTS IN THESE SITUATIONS LATELY, WILL LEAN
ON THE 90TH PERCENTILE WHICH PRODUCES SUSTAINED WINDS OF 15-25KTS
WITH GUSTS ABOUT 10-12KTS HIGHER. LOW LEVEL WARM ADVECTION AND
RISING HEIGHTS ALOFT WILL LEAD TO WARMER HIGHS TUESDAY AFTERNOON.
THE LATEST DETERMINISTIC NBM FALLS VERY NEAR THE MEAN OF GUIDANCE,
HOWEVER MOST OF THE BIAS-CORRECTED GUIDANCE IS 2-5 DEGREES WARMER,
AND THE NBM HAS BEEN TOO COOL IN THESE SITUATIONS. HAVE THEREFORE
BUMPED TEMPERATURES UP A FEW DEGREES OVER NBM TUESDAY AFTERNOON
YIELDING HIGHS RANGING FROM AROUND 60 IN NORTHEAST MISSOURI TO THE
MID AND UPPER 60S ACROSS CENTRAL AND EASTERN MISSOURI INTO SOUTHWEST
ILLINOIS.
CARNEY
LONG TERM
(TUESDAY NIGHT THROUGH SUNDAY)
ISSUED AT 344 AM CDT MON MAR 31 2025
TUESDAY NIGHT THROUGH SATURDAY CONTINUES TO LOOK LIKE AN ACTIVE/WET
PERIOD FOR MUCH OF THE FORECAST AREA. A 60+KT LOW LEVEL JET
DEVELOPS TUESDAY EVENING AHEAD OF THE SYSTEM IN THE PLAINS. THE
RESULTING LOW LEVEL MOISTURE CONVERGENCE WILL LIKELY PRODUCE
SCATTERED SHOWERS AND A FEW STORMS DURING THE EVENING, MAINLY ACROSS
CENTRAL AND NORTHEAST MISSOURI INTO WEST CENTRAL ILLINOIS. GUIDANCE
ALSO HINTS AT CONVECTION OVER THE SOUTHEAST PLAINS SPREADING
NORTHEAST IN THE WARM SECTOR OF THE SYSTEM OVERNIGHT TO AFFECT MORE
OF THE AREA BEFORE SUNRISE WEDNESDAY, SIMILAR TO WHAT HAPPENED LAST
SATURDAY NIGHT/SUNDAY MORNING. MUCAPE VALUES INCREASE TO 1000-1500
J/KG BETWEEN 09-12Z WEDNESDAY AND THE 0-6KM SHEAR IS FORECAST TO BE
50-70KTS. HOWEVER, FORECAST SOUNDINGS SHOW A STRONG LOW LEVEL
INVERSION OVER THE AREA, AND WHILE THE LOW LEVEL WIND FIELDS ARE
STRONG, THE CONVECTION SHOULD BE ELEVATED MAKING HAIL THE PRIMARY
SEVERE THREAT OVERNIGHT. CAN'T ENTIRELY RULE OUT DAMAGING WINDS IF
A STORM CAN MIX DOWN SOME OF THOSE HIGHER WINDS ALOFT, BUT THE
INVERSION LOOKS LIKE IT WILL BE PRETTY TOUGH TOUGH TO GET THROUGH,
AT LEAST UNTIL 12-15Z WEDNESDAY.
GUIDANCE PUSHES THE SURFACE COLD FRONT THROUGH THE AREA DURING THE
DAY WEDNESDAY AND COMBINATION OF DAYTIME HEATING AHEAD OF THE FRONT
AND SURGING DEW POINTS WIPES THE CAP OUT AHEAD OF IT. THE
DETERMINISTIC GFS AND ECMWF REALLY BLOW UP CONVECTION DURING THE
AFTERNOON AHEAD OF THE FRONT AND HAVE IT MOSTLY OUT OF OUR AREA BY
00Z. SBCAPE VALUES STAY IN THE 1000-1500 J/KG RANGE AND 0-6KM SHEAR
INCREASES TO 60-70KTS. THIS IS MORE THAN ENOUGH TO PRODUCE ROTATING
UPDRAFTS, THOUGH THE STORM MODE MAY BE MESSY WITH LOTS OF MERGERS
AND DISCRETE CELLS GROWING UPSCALE INTO CLUSTERS AND LINES AS THE
SHEAR LOOKS CLOSE TO PARALLEL TO THE BOUNDARY. LARGE HAIL AND
DAMAGING WINDS WILL LIKELY BE THE PRIMARY THREATS. ALSO SEEING SOME
CURVATURE IN THE LOWEST 2-3KM OF THE HODOGRAPHS FROM THE GFS SO
THERE WILL BE A TORNADO THREAT AS WELL.
WEDNESDAY LOOKS LIKE OUR LAST CHANCE FOR SEVERE WEATHER FOR A WHILE.
HOWEVER, IT LOOKS LIKE THERE IS AN INCREASING LIKELIHOOD OF HEAVY
RAIN AND POSSIBLY FLOODING FOR THE LATTER HALF OF THE WEEK INTO THE
WEEKEND. THE LOW WHICH PUSHES WEDNESDAY'S COLD FRONT THROUGH OUR
AREA MOVES RAPIDLY NORTHEAST, AND THE LOW LEVEL FRONT BECOMES QUASI-
STATIONARY OVER ARKANSAS EARLY THURSDAY MORNING. PERSISTENT
SOUTHERLY LOW LEVEL FLOW PUSHES GULF MOISTURE INTO THE BOUNDARY
THURSDAY THROUGH SATURDAY. THIS RESULTS IN WAVES OF CONVECTION
THROUGH THAT PERIOD. THERE'S SOME DISAGREEMENT BETWEEN THE
DETERMINISTIC GFS AND ECMWF ON THE TIMING AND LOCATIONS OF THE WAVES
OF HEAVIER RAIN, BUT THE CONSENSUS IN THE LREF IS THAT THE FIRST WILL
BE THURSDAY AFTERNOON/NIGHT, THE SECOND FRIDAY NIGHT, AND THE THIRD
SATURDAY AFTERNOON/EVENING, WITH MOST OF THE QPF ACROSS THE EASTERN
OZARKS. WPC HAS SLIGHT TO MODERATE RISKS FOR EXCESSIVE RAINFALL IN
THEIR OUTLOOKS FOR THAT PERIOD, AND AS MUCH AS 6-8 INCHES OF TOTAL
RAINFALL BY THE TIME THE PATTERN SHIFTS SATURDAY NIGHT. THIS IS
CLOSE TO THE LREF 75TH PERCENTILE QPF, BUT GIVEN AN ENSEMBLE MODEL'S
TENDENCY TO SPREAD OUT THE FOOTPRINT OF QPF AND HAVE AMOUNTS LOWER
THAN WHAT ACTUALLY FALLS, THE 75TH PERCENTILE IS A REASONABLE
FORECAST AT THESE TIME RANGES.
CARNEY
AVIATION
(FOR THE 18Z TAFS THROUGH 18Z TUESDAY AFTERNOON)
ISSUED AT 1144 AM CDT MON MAR 31 2025
THE AREA OF WIDESPREAD STRATUS HAS REALLY BEGUN TO SCATTER OUT THE
PAST COUPLE OF HOURS. THE EXPECTATION IS FOR ALL OF THE TERMINALS
TO BE VFR WITHIN THE NEXT 1-2 HOURS, AND ANY REMNANT MVFR STRATUS
SCATTERING OUT OF SOUTH-CENTRAL ILLINOIS BY MID AFTERNOON.
NORTHWEST WINDS WILL WEAKEN THIS AFTERNOON AS A SURFACE HIGH
APPROACHES. LIGHT/VARIABLE WINDS ARE FORECAST NEAR THIS HIGH
THROUGH MOST OF TONIGHT, WITH WINDS TURNING TO THE SOUTHEAST INTO
TUESDAY MORNING. BY MID MORNING, GUSTS ARE EXPECTED AS WELL NEAR
20 KNOTS.
GOSSELIN
LSX WATCHES/WARNINGS/ADVISORIES
MO...NONE.
IL...NONE.
WFO LSX
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page