718
FXUS63 KLSX 300931
AFDLSX
AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE SAINT LOUIS MO
431 AM CDT THU APR 30 2026
KEY MESSAGES
-THERE IS A 30-60% CHANCE FOR SHOWERS AND A THUNDERSTORM OR TWO THIS
AFTERNOON AND EARLY EVENING.
-SEASONABLY COOL TEMPERATURES WILL CONTINUE THROUGH SATURDAY, NEAR
NORMAL TEMPERATURES AND RAIN CHANCES RETURN SUNDAY THROUGH MID-
WEEK.
SHORT TERM
(THROUGH LATE FRIDAY AFTERNOON)
ISSUED AT 234 AM CDT THU APR 30 2026
THE CENTER OF THE BROAD MID-LEVEL TROUGH HAS SHIFTED INTO THE GREAT
LAKES REGION AND WILL SEND ANOTHER DISTURBANCE THROUGH THE NORTHWEST
FLOW INTO THE MID-MISSISSIPPI VALLEY. THIS FEATURE WILL GENERATE
SHOWERS AND A FEW THUNDERSTORMS ALONG A SOUTHWARD SINKING COLD FRONT
THIS AFTERNOON INTO THE EVENING. POOR MID-LEVEL LAPSE RATES WILL
LIMIT INSTABILITY, ILLUSTRATED BY THE HREF MAX SBCAPE, WHICH PEAKS
AROUND 200 J/KG ALONG AND NORTH OF I-70 DURING THE AFTERNOON. THIS
WILL LIMIT THUNDERSTORM DEVELOPMENT AND KEEP THE REGION FREE FROM
SEVERE THUNDERSTORMS. TEMPERATURES WILL PEAK IN THE 60S TODAY,
WITHIN A DEGREE OR TWO OF YESTERDAY.
THE FRONT WILL BRING ANOTHER SURGE OF BELOW NORMAL AIR INTO THE
REGION OVERNIGHT INTO FRIDAY, COOLING 850 MB TEMPERATURES TO NEAR 0-
2C. THIS WILL RESULT IN EVEN COOLER HIGH TEMPERATURES FRIDAY,
PEAKING IN THE UPPER 50S TO LOW 60S. ANOTHER SURFACE BOUNDARY WILL
DROP SOUTH THROUGH THE REGION FRIDAY AFTERNOON, DRIVEN ALOFT BY YET
ANOTHER MID-LEVEL DISTURBANCE, WITH A 20% CHANCE OF PRODUCING
LIGHT SHOWERS NORTH OF I-70.
DELIA
LONG TERM
(FRIDAY NIGHT THROUGH WEDNESDAY)
ISSUED AT 234 AM CDT THU APR 30 2026
A BROAD SURFACE HIGH WILL PUSH THROUGH THE REGION FRIDAY NIGHT INTO
SATURDAY, SUPPORTING EFFICIENT RADIATIONAL COOLING. COMBINED WITH
THE COOL AIRMASS IN PLACE ACROSS THE REGION, SATURDAY MORNING'S LOWS
WILL BE SOME OF THE COOLEST THIS PERIOD. PORTIONS OF NORTHEAST
MISSOURI, WEST-CENTRAL ILLINOIS, AND THE HOLLOWS OF THE OZARKS ARE
AT GREATEST RISK FOR LIGHT FROST SATURDAY MORNING, WITH A 30-50%
CHANCE OF LOWS 36F OR LOWER.
ENSEMBLE GUIDANCE IS COMING INTO AGREEMENT THAT ANOTHER MID-LEVEL
LOW WILL SURGE SOUTHWARD AND FUJIWARA WITH THE CENTER OF THE MID-
LEVEL TROUGH, RESULTING IN A VERY BROAD TROUGH THAT COVERS THE
EASTERN TWO THIRDS OF THE CONUS FOR THE FIRST HALF OF NEXT WEEK. AT
THE BEGINNING OF THE WORK WEEK A MID-LEVEL DISTURBANCE WILL MOVE
THROUGH THE SOUTHERN PERIPHERY OF THE TROUGH INTO THE MID-
MISSISSIPPI VALLEY. THE RESULTING SURFACE LOW WILL FORM ON THE LEE-
SIDE OF THE ROCKIES AND PUSH EASTWARD THROUGH THE MISSISSIPPI
VALLEY. GUIDANCE IS STARTING TO KEY IN ON SHOWERS AND THUNDERSTORMS
FORMING IN ASSOCIATION WITH THIS LOW AND IT'S ASSOCIATED WARM FRONT
TUESDAY INTO WEDNESDAY.
GUIDANCE DIVERGES IN HOW TO HANDLE THE SURFACE PATTERN BEYOND THE
PASSAGE OF THIS FEATURE, THOUGH AS THE REGION REMAINS ON THE
SOUTHERN PERIPHERY OF THE MID-LEVEL TROUGH, MULTIPLE CHANCES FOR
SHOWERS AND THUNDERSTORMS ARE POSSIBLE THROUGH THE END OF THE PERIOD.
TEMPERATURES WILL RETURN TO NEAR NORMAL VALUES STARTING SUNDAY AS
THE LOW-LEVEL FLOW BECOMES SOUTHWESTERLY, ADVECTING WARM AIR BACK
INTO THE REGION. CONFIDENCE IS HIGH THAT THESE NEAR NORMAL
TEMPERATURES WILL LAST THROUGH THE FIRST PORTION OF THE WEEK, BUT
THE PASSAGE OF THE MID-WEEK SYSTEM HAS THE POTENTIAL BRING COOLER
TEMPERATURES BACK TO THE AREA.
DELIA
AVIATION
(FOR THE 12Z TAFS THROUGH 12Z FRIDAY MORNING)
ISSUED AT 426 AM CDT THU APR 30 2026
RIVER VALLEY FOG HAS FORMED ALONG AND SOUTH OF THE MISSOURI RIVER,
IMPACTING KSUS AND KJEF. THIS FOG WILL LIFT WITH SUNRISE AND THE
ONSET OF DAYTIME MIXING. SHOWERS AND A THUNDERSTORM OR TWO WILL
MOVE THROUGH THE FORECAST AREA ALONG A SOUTHWARD MOVING COLD FRONT
THIS AFTERNOON INTO THE EVENING. THE BEST CHANCE FOR RAIN IS AT
KUIN, WITH LOWER CONFIDENCE FURTHER SOUTH. CONFIDENCE IS LOW IN
THUNDERSTORM DEVELOPMENT, SO HAVE LEFT THE MENTION OF TSRA OUT OF
THE TAFS ENTIRELY FOR THE MOMENT.
WESTERLY WINDS WILL BECOME NORTHWESTERLY BEHIND THE FRONT, AND
THEN LIGHT AND VARIABLE AS A SURFACE HIGH MOVES BACK INTO THE
REGION OVERNIGHT.
DELIA
LSX WATCHES/WARNINGS/ADVISORIES
MO...NONE.
IL...NONE.
WFO LSX
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