883
FXUS63 KLSX 160810
AFDLSX
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ST LOUIS MO
ISSUED BY NATIONAL WEATHER SERVICE KANSAS CITY/PLEASANT HILL MO
310 AM CDT WED JUL 16 2025
KEY MESSAGES
- TODAY WILL BE HOT AND HUMID, WITH HEAT INDEX VALUES OVER 100.
THUNDERSTORMS MOVE IN FROM THE NORTH TONIGHT WITH A LOW
THREAT FOR SEVERE STORMS AND FLASH FLOODING.
- A STALLED FRONT KEEPS SHOWERS AND STORMS AROUND THURSDAY AND
FRIDAY.
- HEAT BUILDS THIS WEEKEND INTO NEXT WEEK, WITH A PROLONGED
STRETCH OF HOT AND HUMID WEATHER LIKELY.
SHORT TERM /THROUGH THURSDAY/
ISSUED AT 310 AM CDT WED JUL 16 2025
RIDGING BECOMES MORE DOMINANT TODAY LEADING TO HOTTER
TEMPERATURES THAN WE HAVE SEEN IN A WHILE. HIGHS AREA WIDE
REACH UP INTO THE 90S. WITH CONTINUED HUMIDITY, THE HEAT INDEX
RISES INTO THE 100 TO 105 DEGREE RANGE THIS AFTERNOON. WHILE
THIS IS CLOSING IN ON DANGEROUS LEVELS, THE DURATION OF THIS
HEAT IS EXPECTED TO ONLY BE ONE DAY, SO WE HAVE OPTED NOT TO
ISSUE A HEAT ADVISORY.
WITH THE RIDGE MORE DOMINANT, WE WONT SEE NEARLY AS MUCH POP
UP SHOWER AND THUNDERSTORM ACTIVITY THIS AFTERNOON. A FEW PULSE
STORMS MAY DEVELOP, BUT THEY WILL BE FEW AND FAR BETWEEN. A
REMNANT CONVECTIVE COMPLEX MOVES BY TO OUR NORTH, STRENGTHENING
AS IT NEARS THE GREAT LAKES, BUT IT IS EXPECTED TO REMAIN NORTH
OF OUR FORECAST AREA TODAY. THE GREATER THREAT FOR THUNDERSTORMS
COMES TONIGHT WHEN THUNDERSTORMS FORM ALONG A SOUTHWARD MOVING
COLD FRONT. THIS ACTIVITY IS EXPECTED TO INITIATE IN THE EVENING,
PUSHING SOUTHWARD INTO THE OVERNIGHT HOURS. SHEAR DOES INCREASE
AS THE FRONT APPROACHES, WITH JUST ENOUGH COMBINATION OF
INSTABILITY AND SHEAR TO PRODUCE A THREAT FOR SOME STORM
ORGANIZATION DURING THE EVENING, BUT STORMS ARE EXPECTED TO
WEAKEN AS THE NIGHT GOES ON AND INSTABILITY WANES. THUS THE
GREATEST THREAT FOR SEVERE THUNDERSTORMS IN OUR AREA IS IN THE
FAR NORTHERN PORTION OF THE FORECAST AREA FROM ABOUT 8PM TO
MIDNIGHT. DAMAGING WINDS ARE THE PRIMARY SEVERE WEATHER THREAT,
THOUGH SLOW MOVING STORMS IN A MOISTURE-RICH ENVIRONMENT MAY ALSO
POSE A THREAT FOR FLASH FLOODING. BOTH OF THESE THREATS WANE AS
THE NIGHT GOES ON AND AS STORMS SHIFT SOUTHWARD.
THE FRONT STALLS IN THE REGION ON THURSDAY, WITH SIGNIFICANTLY
COOLER WEATHER NORTH OF THE FRONT. SOUTH OF THE FRONT, THE HEAT
CONTINUES. THE FRONT SERVES AS A FOCUS FOR ANOTHER ROUND OF
SHOWERS AND STORMS DURING THE AFTERNOON AND EVENING. WHILE THERE
MAY BE JUST ENOUGH SHEAR FOR A LOW SEVERE WEATHER THREAT, THE
GREATER THREAT IS LIKELY LOCALLY HEAVY RAINFALL AND FLASH
FLOODING. THERE IS STILL CONSIDERABLE UNCERTAINTY ON WHERE THE
FRONT STALLS AND THUS WHERE THE GREATEST THUNDERSTORM THREATS
WILL EXIST.
LONG TERM /THURSDAY NIGHT THROUGH TUESDAY/
ISSUED AT 308 AM CDT WED JUL 16 2025
THE FRONT IS LIKELY STILL WITH US ON FRIDAY, BUT IT WILL BE
LOSING ITS DEFINITION WITH TIME AND GRADUALLY LIFTING BACK
TO THE NORTH. SO WHILE WE ARE LIKELY TO SEE ANOTHER ROUND OF
SHOWERS AND STORMS DURING THE AFTERNOON AND EVENING, THEY MAY
NOT BE QUITE AS WIDESPREAD AS THEY ARE ON THURSDAY.
AS WE GET INTO THE WEEKEND, RIDGING BUILDS EVEN MORE OVER THE
SOUTH CENTRAL US, BRINGING THE HOT AND HUMID WEATHER BACK INTO
THE REGION. TEMPERATURES IN THE MID 90S AND DEWPOINTS IN THE
MID 70S WILL COMBINE TO PUSH THE HEAT INDEX BACK OVER 100 AGAIN
AS EARLY AS SATURDAY. THERES MORE UNCERTAINTY ON THIS ACROSS
THE NORTHERN AND EASTERN PORTIONS OF THE AREA THIS WEEKEND AS
SHORTWAVE TROUGHS ROUNDING THE TOP OF THE RIDGE MAY BRING
ROUNDS OF CLOUDS AND THUNDERSTORMS. IF THERE ARE MORE EXTENSIVE
CLOUDS THEN THE HIGHER TEMPERATURES MAY NOT BE REACHED. HOWEVER,
CONFIDENCE IS GREATER IN SOUTHERN AREAS THAT THE HEAT WILL BE
BUILDING BACK IN AGAIN THIS WEEKEND. THE RIDGE CONTINUES TO
BUILD THROUGH NEXT WEEK, WITH GREATER CONFIDENCE THAT THE
WHOLE FORECAST AREA WILL GET IN ON THE HOT AND HUMID WEATHER.
AN EXTENDED PERIOD OF HEAT INDEX VALUES OVER 100 IS
INCREASINGLY LIKELY AS WE GO INTO NEXT WEEK, WHICH WOULD
NECESSITATE A HEAT ADVISORY OR AN EXTREME HEAT WARNING
DEPENDING ON HOW EXTREME THOSE HEAT INDEX VALUES GET. WHILE
THERE MAY BE SOME DAILY VARIATION, THE POSITION AND STRENGTH
OF THE RIDGE NEXT WEEK GIVES US THE STRONGER CONFIDENCE THAT
WE WILL SEE A LONG DURATION PERIOD OF HEAT.
AVIATION /06Z TAFS THROUGH 12Z THURSDAY/
ISSUED AT 308 AM CDT WED JUL 16 2025
(FOR THE 06Z TAFS THROUGH 06Z WEDNESDAY NIGHT)
ISSUED AT 1003 PM CDT TUE JUL 15 2025
SOME PATCHY FOG WILL BE POSSIBLE OVERNIGHT TONIGHT THROUGH EARLY
TOMORROW MORNING, PARTICULARLY AT RIVER VALLEY LOCATIONS.
CONFIDENCE IS LOW THAT WE WILL OBSERVE DENSE FOG LIKE THE PAST TWO
NIGHTS, BUT AT LEAST A BRIEF PERIOD OF VISIBILITY REDUCTIONS WILL
BE POSSIBLE AT FOG PRONE LOCATIONS.
EARLY TOMORROW MORNING, A FEW WEAK SHOWERS WILL BE POSSIBLE,
FIRST AT COU/JEF/UIN, AND FOLLOWED SHORTLY THEREAFTER AT ST. LOUIS
TERMINALS. HOWEVER, THIS ACTIVITY IS NOT LIKELY TO BE IMPACTFUL,
AND PROBABILITIES REMAIN TOO LOW FOR INCLUSION. ADDITIONAL
SHOWERS AND STORMS WILL BE POSSIBLE IN THE AFTERNOON, WITH BEST
CHANCES AT UIN WHERE A PROB30 GROUP HAS BEEN MAINTAINED.
SHOWERS AND THUNDERSTORMS MAY BE MORE LIKELY OVERNIGHT,
PARTICULARLY AT UIN, AND POSSIBLY AT OTHER TERMINALS AS WELL.
HOWEVER, CONFIDENCE IN THE TIMING AND GEOGRAPHIC COVERAGE OF THESE
STORMS REMAINS LOW, AND THIS HAS ONLY BEEN INCLUDED AT UIN FOR
THE TIME BEING WHERE CHANCES ARE GREATEST.
LSX WATCHES/WARNINGS/ADVISORIES
MO...NONE.
IL...NONE.
SHORT TERM...KIMBLE
LONG TERM...KIMBLE
AVIATION...
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