091
FXUS63 KLSX 080317
AFDLSX
AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE SAINT LOUIS MO
1017 PM CDT THU AUG 7 2025
KEY MESSAGES
- SEASONABLY HOT AND HUMID CONDITIONS ARE FORECAST THROUGH THE WEEKEND
WITH THE HIGHEST AFTERNOON HEAT INDEX VALUES NEAR OR JUST ABOVE
100 DEGREES.
- CHANCES OF SHOWERS AND THUNDERSTORMS INCREASES LATE THIS WEEKEND
INTO NEXT WEEK AS A COLD FRONT STALLS OUT IN/NEAR THE REGION.
SHORT TERM
(THROUGH LATE FRIDAY AFTERNOON)
ISSUED AT 159 PM CDT THU AUG 7 2025
SHOWERS AND THUNDERSTORMS HAVE CONTINUED INTO EARLY THIS
AFTERNOON, MAINLY ACROSS NORTHEAST MISSOURI AND WEST-CENTRAL
ILLINOIS NEAR A REMNANT MCV, AS WELL AS PARTS OF EASTERN MISSOURI
AND SOUTHWEST ILLINOIS ON THE WARM AIR ADVECTION WING OF THE MCV.
THESE STORMS HAVE BEEN MOSTLY ON THE WEAK SIDE, AND BELIEVE THAT
WILL CONTINUE GIVEN LATEST SPC MESOANALYSIS ONLY SHOWING ABOUT
15-20 KNOTS OF EFFECTIVE SHEAR. A FEW CORES MAY GET STRONG ENOUGH
TO PRODUCE SOME SMALL HAIL AND GUSTY WINDS IF INSTABILITY IS ABLE
TO INCREASE ENOUGH AHEAD OF THE MCV. THE BEST WINDOW FOR THIS
WOULD BE FROM ABOUT 2200 UTC TO 0100 UTC IN PARTS OF SOUTH-CENTRAL
ILLINOIS. THIS IS CONDITIONAL ON UPSTREAM SHOWERS/THICKER CLOUD
COVER HOWEVER DISSIPATING.
THE REMNANT MCV SHOULD TRACK ACROSS THE MISSISSIPPI RIVER INTO SOUTH-
CENTRAL ILLINOIS BY LATE THIS EVENING. SCATTERED SHOWERS AND A FEW
THUNDERSTORMS ARE FORECAST OVERNIGHT, MAINLY ALONG/EAST OF THE
MISSISSIPPI RIVER THROUGH ABOUT 0900 UTC. THE LOW-LEVEL JET TONIGHT
IS EXPECTED TO BE WEAKER THAN LAST NIGHT, WITH THE ASSOCIATED
MOISTURE CONVERGENCE NOT AS STRONG AND MORE BROAD.
DRY WEATHER IS FORECAST ON FRIDAY AS MID/UPPER LEVEL RIDGING
AMPLIFIES OVER THE MISSISSIPPI VALLEY. MUCH MORE SUNSHINE IS
FORECAST DURING THE DAY ON FRIDAY, WITH 850-HPA TEMPERATURES WARMING
ABOVE +20C FOR MOST OF THE AREA. HIGH TEMPERATURES IN THE LOW TO MID
90S ARE EXPECTED, AND COMBINED WITH SEASONABLY HIGH HUMIDITY LEVELS,
HEAT INDEX VALUES TOPPING OUT AT OR SLIGHTLY ABOVE 100 DEGREES ARE
FORECAST FOR MUCH OF THE AREA.
GOSSELIN
LONG TERM
(FRIDAY NIGHT THROUGH NEXT THURSDAY)
ISSUED AT 159 PM CDT THU AUG 7 2025
(FRIDAY NIGHT - SATURDAY NIGHT)
A CONTINUATION OF THE SEASONABLY HOT/HUMID PATTERN IS LIKELY INTO
EARLY THIS WEEKEND AS THE CENTER OF THE MID/UPPER LEVEL RIDGE
REMAINS LARGELY OVERHEAD. THE RIDGE DOES BEGIN TO WEAKEN EVER SO
SLIGHTLY LATE SATURDAY/SATURDAY NIGHT, WHICH COULD ALLOW FOR A COLD
FRONT TO AT LEAST DROP NEAR FAR NORTHERN SECTIONS OF THE AREA. THIS
IS WHERE THERE ARE LOW CHANCES (20-40%), BUT OTHERWISE DRY WEATHER
IS FORECAST FOR THE REMAINDER OF THE AREA.
(SUNDAY - NEXT THURSDAY)
THE MID/UPPER LEVEL RIDGE WEAKENS A BIT FURTHER LATE THIS WEEKEND
INTO EARLY NEXT WEEK, WITH ENSEMBLE GUIDANCE ALSO SHOWING A TROUGH
MOVING ACROSS THE GREAT LAKES/SOUTHEAST CANADA. THERE IS SOME
VARIABILITY WITH THIS LATTER FEATURE, MAINLY IN TERMS OF STRENGTH.
ABOUT 40% OF MEMBERS FROM THE GRAND ENSEMBLE SHOW A FAIRLY STRONG
TROUGH, WHICH WOULD ALLOW FOR A COLD FRONT TO AT LEAST MAKE IT
THROUGH PORTIONS OF THE AREA. THIS CLUSTER IS ALSO COMPRISED FAIRLY
EQUALLY AMONGST THE GEFS/EPS/GEPS SUITES. HOWEVER, TWO OTHER
CLUSTERS (~40%) OF MEMBERS BARELY SHOW A TROUGH AT ALL, AND WOULD
SUGGEST THE COLD FRONT MAY NOT EVEN MAKE IT INTO OUR NORTHERN
COUNTIES. THIS LEADS TO INCREASING UNCERTAINTY WITH RAIN CHANCES AND
TEMPERATURES OF COURSE. THE OVERALL PATTERN AND CLIMATOLOGY HOWEVER
WOULD FAVOR A STALLING OUT OF THE COLD FRONT SOMEWHERE IN OR NEAR
THE AREA, BRINGING AT LEAST LOW CHANCES (20-30%) OF SHOWERS AND
THUNDERSTORMS THROUGH THE PERIOD. RAIN CHANCES LIKELY WILL BE
FOCUSED IN/NEAR WHEREVER THE FRONTAL BOUNDARY IS DRAPED AND WHEN
SUBTLE DISTURBANCES EMBEDDED WITHIN QUASI-ZONAL FLOW ALOFT MOVE
ACROSS THE FRONT.
GOSSELIN
AVIATION
(FOR THE 06Z TAFS THROUGH 06Z FRIDAY NIGHT)
ISSUED AT 954 PM CDT THU AUG 7 2025
SHOWERS AND THUNDERSTORMS CONTINUE TO DIMINISH TONIGHT AND SHOULD
NO LONGER CAUSE ANY IMPACTS TO TERMINALS. ONCE CHANCES END
COMPLETELY LATE TONIGHT, DRY CONDITIONS WILL PREVAIL THROUGH THE
REST OF THE TAF PERIOD. OTHERWISE, WINDS WILL ELEVATE IN THE
MORNING, BECOMING GUSTY (UP TO 20 KTS) IN CENTRAL AND NORTHEAST
MO AS WELL AS WEST-CENTRAL IL. WINDS WILL DIMINISH IN THE EVENING.
JAJA
LSX WATCHES/WARNINGS/ADVISORIES
MO...NONE.
IL...NONE.
WFO LSX
CLICK HERE TO GO TO PREVIOUS BULLETINS.
Main Text Page