923
FXUS63 KLSX 212353
AFDLSX
AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE SAINT LOUIS MO
653 PM CDT SUN JUN 21 2026
KEY MESSAGES
- DAMAGING WINDS AND TORNADOES ARE POSSIBLE THROUGH THIS EVENING
ACROSS EAST CENTRAL AND SOUTHEAST MISSOURI INTO SOUTHWEST ILLINOIS.
- LOCALLY HEAVY RAINFALL IS ALSO POSSIBLE THROUGH EARLY TONIGHT.
- SEASONABLY COOL CONDITIONS ARE FORECAST THIS WORK WEEK.
SHORT TERM
(THROUGH LATE MONDAY NIGHT)
ISSUED AT 608 PM CDT SUN JUN 21 2026
A SEVERE THUNDERSTORM WATCH HAS BEEN ISSUED FOR OUR SOUTHERN
MISSOURI COUNTIES. THE PRIMARY THREATS WILL BE LARGE HAIL,
DAMAGING WIND GUSTS, AND A POTENTIAL TORNADO OR TWO. SEVERE
THUNDERSTORM WATCH 366 IS IN EFFECT UNTIL 1 AM MONDAY MORNING.
A REMNANT MCV IS CURRENTLY IN SOUTHWEST ILLINOIS AND MOVING
EAST/NORTHEAST. THERE HAS BEEN A VERY SLOW AND GRADUAL UPTICK IN
CONVECTION OUT AHEAD OF THIS FEATURE ACROSS SOUTHWEST AND SOUTH-
CENTRAL ILLINOIS AS DIURNAL INSTABILITY CONTINUES TO INCREASE.
LOW- LEVEL SHEAR AND HELICITY REMAIN QUITE STRONG, SO MINI
SUPERCELLS MAY BE CAPABLE OF PRODUCING TORNADOES. THIS THREAT WILL
CONTINUE AT LEAST OVER THE NEXT FEW HOURS AS THE MCV PROGRESS
THROUGH SOUTH- CENTRAL ILLINOIS.
FARTHER SOUTHWEST, ADDITIONAL SHOWERS AND THUNDERSTORMS ARE EXPECTED
TO DEVELOP FARTHER SOUTHWEST ALONG THE TRAILING COLD FRONT. EXACTLY
WHERE AND WHEN IS NOT CERTAIN, BUT MY BEST GUESS WOULD BE NEAR THE
MISSOURI-KANSAS BORDER WHERE SURFACE CONVERGENCE IS LOCATED. AT
LEAST SCATTERED STORMS SHOULD DEVELOP FARTHER NORTHEAST EVENTUALLY
ALONG THE BOUNDARY, WITH STORMS MOVING EAST/SOUTHEAST IN TIME. HOW
ORGANIZED THIS CONVECTION WILL BE IS ALSO UNCERTAIN AS THERE ARE A
COUPLE OF LIMITING FACTORS INCLUDING: 1) WEAK SURFACE CONVERGENCE
ALONG THE BOUNDARY AND 2) MODEST HEIGHT RISES BEHIND THE MCV. IN
ADDITION, THE PRIOR STORMS HAVE AT LEAST HELPED LIMIT INSTABILITY
SLIGHTLY, WITH MLCAPE VALUES OF 1000-1500 J/KG. EFFECTIVE SHEAR ALSO
DECREASES BEHIND THE MCV, THOUGH IS STILL NEAR 30 KNOTS. A MIXED
MODE OF CONVECTION SEEMS MOST LIKELY, WITH MULTICELLULAR CLUSTERS,
SMALL BOWING SEGMENTS, AND TRANSIENT SUPERCELLS ALL POSSIBLE.
DAMAGING WINDS AND A TORNADO OR TWO ARE POSSIBLE THROUGH LATE
EVENING BEFORE STORMS BEGIN TO MOVE OUT TO THE SOUTHEAST. LOCALLY
HEAVY RAINFALL IS ALSO POSSIBLE GIVEN HIGH PRECIPITABLE WATER VALUES
(~1.9"). AFTERNOON/EVENING STORMS ARE HOWEVER FOCUSED FARTHER
SOUTHWEST. STORMS ALSO SHOULD BE PROGRESSIVE, SO OVERALL I THINK THE
FLASH FLOOD THREAT IS LOW AND LIKELY WOULD BE ISOLATED TO ANY AREAS
THAT DO EXPERIENCE SOME TRAINING.
BAH/ GOSSELIN
LONG TERM
(MONDAY THROUGH NEXT SUNDAY)
ISSUED AT 324 PM CDT SUN JUN 21 2026
(MONDAY - MONDAY NIGHT)
COOLER WEATHER ALONG WITH NORTHERLY WINDS AND CLOUDS ARE
EXPECTED ON MONDAY. HIGH TEMPERATURES ARE ONLY EXPECTED TO REACH
INTO THE MID 70S, OR ABOUT 10 DEGREES BELOW NORMAL FOR THE DATE.
LOWS MONDAY NIGHT ARE FORECAST TO DROP INTO THE MID 50S TO NEAR THE
60 DEGREE MARK.
(TUESDAY - NEXT SUNDAY)
NOT MUCH HAS CHANGED WITH RESPECT TO THE WORK WEEK FORECAST WITH
BROAD NORTHWEST FLOW ALOFT ACROSS THE MISSISSIPPI VALLEY. THERE IS
HIGH CONFIDENCE IN SEASONALLY COOL TEMPERATURES WITH MOSTLY DRY
WEATHER EXPECTED OUTSIDE OF A COLD FRONTAL PASSAGE
WEDNESDAY/WEDNESDAY NIGHT.
MODERATING TEMPERATURES ARE FORECAST HEADING INTO NEXT WEEKEND WITH
FLOW ALOFT BECOMING MORE ZONAL. THAT MEANS INCREASING
MOISTURE/INSTABILITY AS WELL AND INCREASING CHANCES OF SHOWERS AND
THUNDERSTORMS.
GOSSELIN
AVIATION
(FOR THE 00Z TAFS THROUGH 00Z MONDAY EVENING)
ISSUED AT 632 PM CDT SUN JUN 21 2026
THERE CURRENTLY ARE TWO SURFACE COLD FRONTS ACROSS THE REGION. THE
FIRST COLD FRONT IS LOCATED SOUTHEAST OF KUIN AND NORTHWEST OF
KSTL. SHOWERS AND THUNDERSTORMS HAVE GENERALLY STRUGGLED TO
MAINTAIN THEMSELVES WITH THIS NORTHERN FRONT, WITH NOT MUCH
LIGHTNING BEING OBSERVED. THIS IS LIKELY DUE TO THE MORE LIMITED
INSTABILITY AND WEAK SUBSIDENCE UPSTREAM OF THE MCV. THE SECONDARY
COLD FRONT, IS LOCATED NEAR A CRAWFORD TO RANDOLPH COUNTY LINE
AND IS WHERE MORE ROBUST AND EVEN SEVERE THUNDERSTORMS EXIST.
THE SURFACE COLD FRONT TO THE NORTHWEST IS WHAT WILL AFFECT THE
STL TERMINALS OVERNIGHT. HOWEVER, HAVE NOT INCLUDED THE MENTION OF
THUNDER IN THE STL TERMINALS GIVEN THE WANING INSTABILITY. BEHIND
THE COLD FRONT, WINDS WILL VEER AROUND FROM THE NORTHWEST AT ABOUT
10 KTS WITH SOME GUSTS POSSIBLE. THE OTHER IMPACT TO THE TERMINALS
WILL BE THE RAPIDLY DECREASING CIGS AS IFR FILTERS IN FROM THE
NORTHWEST. FORECAST SOUNDINGS SHOW ALL TERMINALS GOING IFR
OVERNIGHT INTO THE MONDAY MORNING HOURS. A SLOW RECOVERY TO VFR
IS EXPECTED IN THE AFTERNOON HOURS FROM NORTHWEST TO SOUTHEAST.
BAH
LSX WATCHES/WARNINGS/ADVISORIES
MO...FLOOD WATCH UNTIL 1 AM CDT MONDAY FOR FRANKLIN MO-SAINT CHARLES
MO-SAINT LOUIS CITY MO-SAINT LOUIS MO.
FLOOD WATCH THROUGH MONDAY MORNING FOR CRAWFORD MO-IRON MO-
JEFFERSON MO-MADISON MO-REYNOLDS MO-SAINT FRANCOIS MO-
SAINTE GENEVIEVE MO-WASHINGTON MO.
FLOOD WATCH UNTIL 7 PM CDT THIS EVENING FOR BOONE MO-CALLAWAY MO-
COLE MO-GASCONADE MO-LINCOLN MO-MONITEAU MO-MONTGOMERY MO-
OSAGE MO-WARREN MO.
IL...FLOOD WATCH UNTIL 1 AM CDT MONDAY FOR BOND IL-FAYETTE IL-GREENE
IL-JERSEY IL-MACOUPIN IL-MADISON IL-MONTGOMERY IL.
FLOOD WATCH THROUGH MONDAY MORNING FOR CLINTON IL-MARION IL-
MONROE IL-RANDOLPH IL-SAINT CLAIR IL-WASHINGTON IL.
FLOOD WATCH UNTIL 7 PM CDT THIS EVENING FOR CALHOUN IL.
WFO LSX
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