942
FXUS63 KLSX 180859
AFDLSX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE SAINT LOUIS MO
359 AM CDT SUN MAY 18 2025
KEY MESSAGES
- STRONG TO SEVERE STORMS ARE POSSIBLE TONIGHT. SOME OF THE STORMS
MAY PRODUCE LOCALLY HEAVY RAIN.
- THE CHANCE FOR STRONG TO SEVERE THUNDERSTORMS CONTINUES MONDAY
AFTERNOON AND MONDAY NIGHT. LOCALLY HEAVY RAIN CONTINUES TO BE
POSSIBLE WITH THESE STORMS.
SHORT TERM
(THROUGH TUESDAY)
ISSUED AT 357 AM CDT SUN MAY 18 2025
AN AREA OF MAINLY STRATIFORM RAIN IS MOVING THROUGH SOUTH CENTRAL IN
TO SOUTHEAST MISSOURI THIS MORNING. THERE IS AN ISOLATED
THUNDERSTORM OR TWO, BUT THIS PRECIP HAS BEEN WEAKENING ALL MORNING,
AND I EXPECT THIS TREND TO CONTINUE UNTIL THE PRECIPITATION
DISSIPATES ENTIRELY BETWEEN 12Z-15Z. EXPECT THE REMAINDER OF THE
DAY TO BE DRY UNDER THE INFLUENCE OF UPPER LEVEL RIDGING, WITH
TEMPERATURES NEAR NORMAL IN THE MID TO UPPER 70S.
SHORT RANGE DETERMINISTIC MODELS VARY IN HOW THE NEXT ROUND OF
CONVECTION DEVELOPS TONIGHT. THE GENERAL CONSENSUS IS THAT
THUNDERSTORMS WILL FORM OVER EASTERN KANSAS LATE THIS AFTERNOON IN
RESPONSE TO CONVERGENCE ALONG THE WARM FRONT, AND AN INCREASING LOW
LEVEL JET. DISCRETE STORMS THEN GROW UPSCALE INTO AN MCS DURING THE
EVENING, AND THIS MCS MOVES EAST THROUGH THE NIGHT. THE EVOLUTION
OF THE MCS THROUGH THE NIGHT VARIES PRETTY WIDELY THOUGH. THE MCS
WILL BE RUNNING INTO MID/UPPER LEVEL RIDGING AND BROAD SCALE
SUBSIDENCE OVER THE MISSISSIPPI VALLEY THE FARTHER EAST IT MOVES.
WHILE MOST MODELS SHOW THE MCS MAKING IT INTO OUR FORECAST AREA BY
04Z-06Z MONDAY, THERE ARE SEVERAL THAT WEAKEN THE CONVECTION TO
LITTLE MORE THAN DISSIPATING SHOWERS DUE TO THE INFLUENCE OF THE
RIDGE AND WEAKENING INSTABILITY BY THE TIME IT GETS TO CENTRAL
MISSOURI. THE RAP MAY BE THE MOST EXTREME EXAMPLE OF THIS WEAKENING
TREND WITH ONLY ISOLATED SPOTS OF A TENTH OR TWO OF QPF IN OUR AREA
TONIGHT. THIS IS IN CONTRAST TO THE VERY WET GFS THAT PRINTS OUT
AREAS 2-3 INCHES OF QPF ACROSS PARTS OF MISSOURI TONIGHT. NOT QUITE
READY TO EITHER ISSUE A FLOOD WATCH, OR PULL ALL THE POPS. HOWEVER
THE SEVERE WEATHER THREAT FOR TONIGHT DOES NOT LOOK AS SERIOUS AS IT
DID IN PREVIOUS MODEL RUNS WITH MUCAPE STRUGGLING TO CRACK 1000 J/KG
IN MOST LOCATIONS. WEAKER CONVECTION ALSO LENDS TO A LOWER HEAVY
RAIN THREAT.
THE GUIDANCE IS ALSO SHOWING LOWER INSTABILITY OVER CENTRAL AND
EASTERN MISSOURI INTO SOUTHWEST ILLINOIS THAN PREVIOUS RUNS FOR
MONDAY AND MONDAY NIGHT. MODELS NOW SHOW THE WARM FRONT STRETCHING
FROM FAR SOUTHERN ILLINOIS NORTHWEST TO NEAR ST. JOSEPH MISSOURI
MONDAY AFTERNOON WHERE IT WAS FARTHER NORTH ALONG THE MISSOURI/IOWA
BORDER IN PREVIOUS RUNS. AFTERNOON MLCAPE VALUES OVER MUCH OF OUR
FORECAST AREA ARE ANYWHERE FROM 500-1000 J/KG LOWER ACROSS CENTRAL
AND NORTHEAST MISSOURI THAN PREVIOUSLY FORECAST. THE CAPE PROFILES
IN FORECAST SOUNDINGS ARE NOT AS WIDE, AND THERE APPEARS TO NOT BE
AS MUCH CAPE IN THE HAIL GROWTH ZONE. DEEP LAYER SHEAR IS ALSO NOT
QUITE AS IMPRESSIVE, BUT STILL RESPECTABLE AT AROUND 40KTS. TO BE
CLEAR, THE PARAMETER SPACE IS STILL SUFFICIENTLY STRONG TO PRODUCE
SEVERE THUNDERSTORMS MONDAY AFTERNOON AND EVENING, BUT THE TREND IS
FOR CONDITIONS TO BE A LITTLE LESS FAVORABLE. HODOGRAPHS SHOW MORE
LOW LEVEL CURVATURE OVER OUR AREA DUE TO BACKED WINDS IN THE VICINITY
OF THE WARM FRONT, SO THERE MAY ACTUALLY BE MORE OF A TORNADO THREAT
IN THIS SCENARIO DESPITE THERE BEING LESS INSTABILITY. THUNDERSTORMS
WILL BE CAPABLE OF PRODUCING LOCALLY HEAVY RAIN AGAIN WHICH COULD
LEAD TO MINOR FLOODING ON SMALLER RIVERS AND STREAMS.
THE STACKED LOW PRESSURE SYSTEM WILL FINALLY MOVE INTO THE MIDWEST
AND PUSH THE ASSOCIATED COLD FRONT THROUGH THE MISSISSIPPI VALLEY.
AFTERNOON MLCAPE RISES TO 1500-2000 J/KG AGAIN AHEAD OF THE FRONT
ALONG AND EAST OF THE MISSISSIPPI RIVER WHICH ALONG WITH 0-6KM SHEAR
WOULD BE SUFFICIENT FOR ANOTHER ROUND OF SEVERE THUNDERSTORMS
TUESDAY AFTERNOON. HOWEVER FORECAST SOUNDINGS SHOW A WEAK CAP THAT
WILL NEED TO BE BROKEN. CONVERGENCE ALONG THE FRONT DOESN'T LOOK
LIKE THE BEST AS LOW LEVEL FLOW IN THE WARM SECTOR IS FROM THE
SOUTHWEST AND FLOW BEHIND THE FRONT IS FROM THE WEST. THE THREAT
FOR SEVERE STORMS WILL THEREFORE BE CONDITIONAL ON IF AND WHEN
STORMS ACTUALLY DEVELOP.
CARNEY
LONG TERM
(WEDNESDAY THROUGH SATURDAY)
ISSUED AT 357 AM CDT SUN MAY 18 2025
MEDIUM RANGE GUIDANCE SHOWS THE PRIMARY COLD FRONT WELL SOUTH OF THE
AREA BY 12Z WEDNESDAY AND A SECONDARY COLD FRONT MOVING THROUGH
DURING THE DAY. THE FRONT WILL BE PUSHED THROUGH BY ONE LAST VORT
MAX ROTATING AROUND THE THE MID/UPPER LOW OVER THE GREAT LAKES. GFS
AND ECMWF SHOW ENOUGH MOISTURE REMAINING TO PRODUCE SCATTERED
SHOWERS AS THE FRONT AND VORT MAX MOVE THROUGH ON WEDNESDAY, BUT
ADDITIONAL RAINFALL AMOUNTS SHOULD BE INCONSEQUENTIAL COMPARED TO
EARLIER IN THE WEEK. COOL HIGH PRESSURE BUILDS INTO THE MISSISSIPPI
VALLEY FOR THE END OF THE WEEK. THOUGH WEDNESDAY WILL LIKELY BE THE
COOLEST DAY DUE TO CLOUD COVER AND POTENTIAL SHOWERS, THURSDAY AND
FRIDAY'S TEMPERATURES WILL ALSO BE BETWEEN 5 TO 10 DEGREES BELOW
NORMAL IN THE MID 60S TO LOW AND MID 70S. THE HIGH MOVES INTO THE
OHIO VALLEY ON SATURDAY WHICH TURNS THE LOW LEVEL FLOW BACK TO A
SOUTHERLY DIRECTION BRINGING WARMER TEMPERATURES IN THE MID TO UPPER
70S, ALONG WITH MOISTURE RETURN AND A CHANCE FOR PRECIPITATION.
CARNEY
AVIATION
(FOR THE 06Z TAFS THROUGH 06Z SUNDAY NIGHT)
ISSUED AT 1050 PM CDT SAT MAY 17 2025
LIGHT AND VARIABLE SURFACE FLOW WILL PERSIST INTO SUNDAY WITH A
SLIGHT UPTICK IN WIND SPEEDS AFTER SUNRISE. DESPITE THIS,
KUIN AND METRO TERMINALS WILL REMAIN NEAR OR BELOW 5 KNOTS AS
WINDS VEER OUT OF THE SOUTHEAST AHEAD OF A WARM FRONT SUNDAY
EVENING. KJEF/KCOU SHOULD SEE WIND CREEP UP A BIT SOONER WITH
EASTERLY WIND OF 5-10 KNOTS CONTINUING TO VEER THROUGH 00Z. WE
WILL BE WATCHING A FEW SHOWERS AND WEAKENING THUNDERSTORMS THAT
ARE EXPECTED TO GLANCE CENTRAL MISSOURI OVERNIGHT INTO EARLY
SUNDAY MORNING. WHILE KJEF/KCOU COULD BE IMPACTED, IT DOESN'T LOOK
LIKE A WIDESPREAD, LONG DURATION EVENT AND HIT OR MISS ACTIVITY
MAKES IT DIFFICULT TO PINPOINT WHEN OR IF EITHER SITE WILL BE
DIRECTLY IMPACTED. THEREFORE, PREVAILING CONDITIONS LEAVE THIS
MENTION OUT, ESPECIALLY SINCE LATEST DATA CONTINUES TO TRENDS
SLIGHTLY SOUTH WITH THIS ACTIVITY.
THE WARM FRONT PREVIOUSLY MENTIONED WILL APPROACH LATE SUNDAY
AFTERNOON INTO THE EVENING WITH THUNDERSTORMS DEVELOPING ALONG AND
AHEAD OF THE BOUNDARY. SOME THUNDERSTORMS COULD BE STRONG TO
SEVERE AS THEY INITIALIZE TO THE WEST. GUIDANCE DEPICTS A VARIETY
OF SOLUTIONS, WHICH ISN'T ALL THAT ATYPICAL HEADING INTO SUMMER-
LIKE CONVECTION, LEAVING UNCERTAINTY IN THE EXACT TIME OF ARRIVAL
AND INTENSITY. GENERAL TRENDS WOULD SUGGEST THUNDERSTORM POTENTIAL
WILL REACH CENTRAL MISSOURI AROUND 00Z AT THE EARLIEST, SPREADING
EASTWARD INTO THE METRO TERMINALS THROUGH THE MIDNIGHT HOUR. SOME
SOLUTIONS LAG WELL BEHIND THIS TIMING, BUT ARE OUTLIERS.
THUNDERSTORMS WILL LIKELY RESULT IN IMPACTS VIA LOWERING CLOUD
BASES, POTENTIAL FOR VISIBILITY REDUCTION WITHIN THUNDERSTORMS AND
GUSTY WINDS. MVFR CONDITIONS ARE LIKELY WITH LOWER CATEGORIES
POSSIBLE IF THUNDERSTORMS MAINTAIN INTENSITY SUNDAY NIGHT.
MAPLES
LSX WATCHES/WARNINGS/ADVISORIES
MO...NONE.
IL...NONE.
WFO LSX
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