429
FXUS63 KLSX 161730
AFDLSX
AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE SAINT LOUIS MO
1230 PM 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...HURST 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. THERE'S 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
(FOR THE 18Z TAFS THROUGH 18Z THURSDAY AFTERNOON)
ISSUED AT 1224 PM CDT WED JUL 16 2025
CONVECTION HAS BEGUN TO SPECKLE THE FORECAST AREA THIS AFTERNOON
AND IS EXPECTED TO PERSIST UNTIL SUNDOWN. THE GREATEST POTENTIAL
FOR IMPACTS TODAY WILL BE LATE THIS AFTERNOON INTO THIS EVENING AT
THE ST. LOUIS METROPOLITAN TERMINALS, BUT EVEN SO CONFIDENCE IN A
DIRECT HIT BY A THUNDERSTORM IS LOW. A COLD FRONT WILL INCH ITS
WAY SOUTH TONIGHT, SWITCHING WINDS FROM SOUTHWESTERLY TO NORTHERLY
AS IT PASSES. THIS FRONT WILL BRING ANOTHER ROUND OF SHOWERS AND
THUNDERSTORMS TO THE AREA, IMPACTING MAINLY AREAS NORTH OF I-70
THROUGH TOMORROW MORNING. OTHERWISE, DRY AND VFR CONDITIONS WILL
EXIST FOR ALL SITES THAT ARE NOT IMPACTED BY SHOWERS OR THUNDERSTORMS
DURING THE PERIOD.
JAJA
LSX WATCHES/WARNINGS/ADVISORIES
MO...NONE.
IL...NONE.
WFO LSX
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