375
FXUS63 KLSX 291802
AFDLSX
AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE SAINT LOUIS MO
102 PM CDT SAT MAR 29 2025
KEY MESSAGES
- SHOWERS WILL IMPACT PORTIONS OF SOUTHEAST AND EAST-CENTRAL
MISSOURI AND SOUTHWEST ILLINOIS TODAY.
- A FEW SEVERE THUNDERSTORMS ARE POSSIBLE LATE TONIGHT IN CENTRAL
AND NORTHEAST MISSOURI AND WEST-CENTRAL ILLINOIS. DAMAGING WINDS AND
LARGE HAIL ARE THE MAIN THREAT.
- SEVERE THUNDERSTORMS ARE LIKELY ON SUNDAY AFTERNOON AND EARLY
EVENING WITH ALL HAZARDS POSSIBLE INCLUDING LARGE HAIL, DAMAGING
WINDS, AND A FEW TORNADOES.
SHORT TERM
(THROUGH LATE SUNDAY AFTERNOON)
ISSUED AT 338 AM CDT SAT MAR 29 2025
SHOWERS HAVE BEEN EXPANDING ACROSS SOUTHEAST MO AND SOUTHWEST IL
DURING THE LAST FEW HOURS AS THE SOUTHWESTERLY LLJ PROMOTES WAA
AND MOISTURE TRANSPORT/CONVERGENCE AND THE FIRST IN A SERIES OF
VORT MAXES LIFTS NORTHEASTWARD. ADDITIONAL VORT MAXES WILL TRACK
NORTHEAST ACROSS THE SOUTHEAST HALF OF THE CWA TODAY ATTENDANT
WITH THE WEAKENING/LIFTING UPPER TROF CENTERED THROUGH THE LOWER
MS VALLEY. THESE DISTURBANCES IN TANDEM WITH A PERSISTENT LLJ AND
INCREASING MOISTURE CONVERGENCE WILL RESULT IN EXPANDING COVERAGE
OF SHOWERS PEAKING LATER THIS MORNING, WITH AN EASTWARD SHIFT AND
DIMINISHING COVERAGE THIS AFTERNOON. THE GREATEST CONCENTRATION
WILL BE THROUGH SE MO AND SW IL WITH THE ST. LOUIS REGION ON THE
NORTHWEST PERIPHERY. THE CLOUDS AND PRECIPITATION WILL SUPPRESS
HIGHS TO ONLY IN THE UPPER 60S IN THE AFOREMENTIONED AREA WITH
READINGS IN THE 70S FURTHER WEST AND NORTHWEST THROUGHOUT CENTRAL
AND NORTHEAST MO.
A MORE CONVECTIVELY ACTIVE PERIOD AND OUR FIRST REAL THREAT OF ANY
SEVERE STORMS WILL COME LATER TONIGHT, PREDOMINATELY THROUGH CENTRAL
AND NORTHEAST MO AND PERHAPS WEST-CENTRAL IL. THE OVERALL SCENARIO
HAS NOT CHANGED DRAMATICALLY. STRONG-SEVERE THUNDERSTORMS INITIATING
WELL TO THE WEST ACROSS OK/EASTERN KS WILL ORGANIZE INTO A QLCS AND
MOVE INTO WESTERN MO AND EVENTUALLY TRACK INTO CENTRAL AND NORTHEAST
MO OVERNIGHT. HOW MUCH BARK IS LEFT WITH THE STORMS IS THE CENTRAL
QUESTION. THERE ARRIVAL SHOULD BE PRECEDED BY INCREASING LOW-LEVEL
MOISTURE TRANSPORT AND INCREASING INSTABILITY WITH THE SREF SHOWING
A 50+ PERCENT CHANCE OF 500+ J/KG OF SBCAPE MOVING INTO AT LEAST
CENTRAL MO IN ADVANCE OF THEM ALONG WITH INCREASING DEEP LAYER
SHEAR. CAMS ARE A BIT VARIED WITH ORGANIZATION AND INTENSITY,
HOWEVER IT IS GREATEST IN CENTRAL AND NORTHEAST MO, DIMINISHING AS
THE ACTIVITY QUICKLY MOVES EAST EARLY ON SUNDAY MORNING. PRESENT
INDICATIONS ARE THE REMNANT SHOWERS/STORMS WILL EITHER EXIT THE
CWA AND OR DISSIPATE THE 15Z OR SO. ANY SEVERE STORMS WILL POSE
MAINLY A THREAT OF DAMAGING WINDS AND LARGE HAIL.
CUMULATIVELY THE LATEST GUIDANCE CONTINUES TO SUPPORT THE GREATEST
SEVERE WEATHER THREAT ON SUNDAY AFTERNOON AND EVENING, HOWEVER THERE
ARE SOME INTRICATE DETAILS THAT COULD ULTIMATELY MODULATE THE
EXPANSE OF THE THREAT AND INTENSITY, AND ALSO FAILURE MODES WHICH
COULD LIMIT THE SEVERE THREAT.
A BROAD AND PROGRESSIVE UPPER TROF WITH EMBEDDED SERIES OF LOW-
AMPLITUDE DISTURBANCES WILL MOVE ACROSS THE AREA DURING THE DAY
AND EVENING AND OF COURSE THE MODELS HAVE DIFFERENCES WITH THESE
DISTURBANCES. THE DISTURBANCES SHOULD AT LEAST PARTIALLY GUIDE THE
CONVECTION AND MORESO THE PROGRESS OF THE ADVANCING COLD FRONT.
THE MOST UNCOMPLICATED SCENARIO IS THE AIR MASS RECOVERS IN THE
WAKE OF THE MORNING STORMS WITH ROBUST INSTABILITY BY EARLY-MID
AFTERNOON AND SEVERE STORMS INITIATING ALONG THE COLD FRONT AS
ADVANCES ACROSS ERN MO/SERN MO AND SW IL FROM THE AFTERNOON INTO
THE EARLY EVENING. THE DEEP LAYER SHEAR VECTORS HAVE A BIT MORE
FRONT PARALLEL ORIENTATION PRIOR TO 00Z BUT THEN GET INCREASINGLY
ORTHOGONAL AFTER 00Z. I THINK ULTIMATELY THE ORIENTATION WILL BE
TIED TO THE DISTURBANCES AND THEIR MOTION. AT LEAST SEMI-DISCRETE
SUPERCELLS SEEM PROBABLE AND SOME OF THE CAMS SHOW EVEN A MORE
DISCRETE MODE ACROSS SE MO/SW IL AND POSSIBLY A LINE OF BROKEN
SUPERCELLS.
ALL SEVERE HAZARDS REMAIN POSSIBLE: LARGE HAIL, DAMAGING WINDS
AND A FEW TORNADOES. SANS SE MO AND SW IL, THE GENERAL CONSENSUS
IS THE SURFACE WINDS IN THE WARM SECTOR AHEAD OF THE FRONT WILL BE
A BIT MORE VEERED THUS LIMITING HODOGRAPH CURVATURE AND SRH, AND
A LOWER TORNADO THREAT THAN WE THOUGHT 24 HOURS AGO. THE WINDS
REMAIN A BIT MORE BACKED IN SE MO AND SW IL SUGGESTING A HIGHER
TORNADO THREAT IN THAT AREA.
SO WHAT ARE THE LIMITING FACTORS AND POTENTIAL FAILURE MODES:
1) FASTER SPEED OF THE COLD FRONT. SOME OF THE MODELS HAVE A ST.
LOUIS FROPA AROUND 18Z AND A CWA-WIDE FROPA BY 00Z. THIS WOULD
PROBABLY LIMIT SEVERE STORMS TO MAINLY SE MO AND SW IL.
2) A RESIDUAL BOUNDARY FROM THE MORNING STORMS CHOPPING INTO THE
SYNOPTIC WARM SECTOR, LIMITING THE NORTHWARD EXTENT ACROSS EASTERN
MO. AGAIN WOULD PROBABLY FAVOR SOUTH/EAST OF ST. LOUIS FOR BEST
SEVERE THREAT.
3) A GRAVITY WAVE/EXTENSIVE CLOUDS FROM THE MORNING MCS COULD
SUPPRESS THINGS SOUTHWARD BY LIMITING AIR MASS RECOVERY.
4) EARLY DEVELOPMENT OF CONVECTION IN THE MORNING ACROSS SW MO
THAT WOULD MOVE NORTHEASTWARD THROUGH THE WARM SECTOR AND LIMIT
INSTABILITY AND THE NORTHWARD EXTENT OF SEVERE CHANCES.
CURRENT THINKING IS THE BEST SEVERE WEATHER CHANCES WILL RESIDE
ALONG AND SOUTH OF A LINE FROM AROUND BLAND MO TO WENTZVILLE MO
TO LITCHFIELD IL. SE MO AND SW IL SEEMS ESPECIALLY VULNERABLE WITH
POTENTIALLY SEVERAL LONG-LIVED SUPERCELLS.
GLASS
LONG TERM
(SUNDAY NIGHT THROUGH FRIDAY)
ISSUED AT 338 AM CDT SAT MAR 29 2025
NORTHWEST WINDS WILL ADVECT DRIER AND MUCH COOLER AIR INTO THE
CWA IN THE WAKE OF THE COLD FRONT LATER SUNDAY NIGHT, CONTINUING
INTO MONDAY AS SURFACE HIGH PRESSURE MOVES INTO THE MS VALLEY.
HIGH TEMPERATURES WILL FALL TO BELOW NORMAL LEVELS AND WILL MAINLY
BE IN THE 50S. RISING HEIGHTS ALOFT ON TUESDAY AND THE RETREAT OF
THE SURFACE RIDGE/HIGH WILL ALLOW FOR THE ONSET OF A EVOLVING WAA
REGIME WITH SE-S LOW-LEVEL FLOW. ACCORDINGLY TEMPERATURES WILL
BEGIN TO MODERATE UPWARD.
GUIDANCE IS BEGINNING TO HONE IN ON ANOTHER DYNAMIC SYSTEM FEATURING
A POTENT UPPER TROF LIFTING THROUGH THE CENTRAL U.S., AND A
NORTHEASTWARD TRACKING SURFACE LOW AND TRAILING/ADVANCING COLD FRONT
ON WEDNESDAY. LIKE YESTERDAY, DIFFERENCES PERSIST IN THE ENSEMBLES
SUCH AS MOISTURE RECOVERY AND AVAILABLE INSTABILITY, AS WELL AS
TIMING AND STRENGTH OF THE UPPER TROF AND BOUNDARY. THIS SYSTEM WILL
NEED TO BE CLOSELY MONITORED FOR POSSIBLY ANOTHER BOUT OF STRONG-
SEVERE STORMS BUT CONFIDENCE IS MEASURED AT THIS TIME.
GLASS
AVIATION
(FOR THE 18Z TAFS THROUGH 18Z SUNDAY AFTERNOON)
ISSUED AT 1247 PM CDT SAT MAR 29 2025
THE LIGHT RAIN HAS MOVED OUT OF THE ST. LOUIS AREA AIRPORTS AND
MAINLY DRY CONDITIONS ARE NOW EXPECTED THROUGH THIS EVENING. OTHER
THAN SOME LOW VFR CEILINGS EARLY THIS EVENING AT COU/JEF/UIN,
MAINLY MVFR CEILINGS ARE EXPECTED DURING THE PERIOD WITH CEILINGS
FALLING BELOW 2000 FEET AGL BY LATE TONIGHT. SHOWERS AND
THUNDERSTORMS WILL MOVE INTO COU/JEF AROUND 08Z AND MOVE EAST INTO
UIN/STL/SUS/CPS BY 10-12Z. SOME OF THE HEAVIER SHOWERS AND
THUNDERSTORMS WILL BE CAPABLE OF REDUCING CEILINGS AND
VISIBILITIES TO IFR CONDITIONS AND PRODUCE WIND GUSTS OVER 35
KNOTS. WINDS WILL BE OUT OF THE SOUTH TODAY, BUT WILL TURN OUT OF
THE SOUTHWEST AND WEST ON SUNDAY MORNING. THERE IS CHANCE OF
ADDITIONAL THUNDERSTORMS EARLY ON SUNDAY AFTERNOON, BUT I HAVE NOT
INCLUDED THEM IN THE STL TAF AS THEY MAY DEVELOP JUST TO THE
SOUTH AND EAST OF THE TERMINAL.
BRITT
LSX WATCHES/WARNINGS/ADVISORIES
MO...NONE.
IL...NONE.
WFO LSX
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page