548  
FXUS63 KLSX 192025  
AFDLSX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE SAINT LOUIS MO  
325 PM CDT FRI JUL 19 2019  
   
SHORT TERM
 
(THROUGH LATE SATURDAY AFTERNOON)  
ISSUED AT 322 PM CDT FRI JUL 19 2019  
 
LITTLE TO NO CHANGE IN THE FORECAST THROUGH SATURDAY AS THE ONGOING  
HEAT WAVE WILL CONTINUE. WELL ABOVE NORMAL TEMPERATURES ARE EXPECTED  
BOTH FOR TONIGHT AND ON SATURDAY, WITH BASICALLY A PERSISTENCE  
FORECAST. LOWS TONIGHT SHOULD BE IN THE 70S TO NEAR 80 DEGREES WITH  
HIGHS ON SATURDAY IN THE MID TO UPPER 90S. PEAK HEAT INDEX VALUES  
DURING THE AFTERNOON HOURS SHOULD REACH THE 100-110 RANGE SIMILAR TO  
THE PAST TWO DAYS.  
 
GOSSELIN  
 
   
LONG TERM
 
(SATURDAY NIGHT THROUGH NEXT FRIDAY)  
ISSUED AT 322 PM CDT FRI JUL 19 2019  
 
THE MAIN FOCUS IN THE SATURDAY NIGHT INTO SUNDAY TIMEFRAME CONTINUES  
TO BE ON THE TIMING OF AN APPROACHING COLD FRONT. THIS FRONTAL  
TIMING IS EXPECTED TO HAVE LARGE RAMIFICATIONS ON HIGH TEMPERATURES  
SUNDAY, AND THE POSSIBILITY OF ONE FINAL DAY OF HEAT/HUMIDITY.  
 
SUBTLE CHANGES HAVE BEEN NOTED SINCE YESTERDAY WITH RESPECT TO THE  
TIMING, WITH THE NAM STILL THE FASTEST SOLUTION AND THE ECMWF ON THE  
SLOWER SIDE. THE LATEST 1200 UTC GFS HAS SLOWED DOWN COMPARED TO  
YESTERDAY, MORE IN LINE WITH LAST NIGHT'S ECMWF. GIVEN THE  
UNCERTAINTY THAT STILL EXISTS WITH THIS FRONT, DID NOT DEVIATE MUCH  
FROM THE PREVIOUS FORECAST AND WILL ELECT TO NOT MAKE ANY CHANGES TO  
THE ONGOING HEAT PRODUCTS. HOWEVER, IT REMAINS POSSIBLE THAT ONE  
ADDITIONAL DAY MAY BE NEEDED FOR THESE PRODUCTS ACROSS THE  
SOUTHEASTERN HALF OR SO OF THE CWA DEPENDING ON THE EXACT SPEED OF  
THE AFOREMENTIONED FRONT. ANOTHER POSSIBILITY THAT WAS MENTIONED  
YESTERDAY IS THAT ORGANIZED CONVECTION TO OUR NORTH ACCELERATES  
SOUTHWARD FROM THE SYNOPTIC COLD FRONT AND PUSHES AN EFFECTIVE  
BOUNDARY EQUATORWARD. THIS WOULD HELP BRING STORM CHANCES AND  
PLENTY OF THICKER CLOUDS FAR ENOUGH SOUTH TO PRECLUDE THE  
NECESSITY OF ANY HEAT HEADLINE EXTENSIONS.  
 
STORMS SUNDAY AFTERNOON/EVENING MAY BE STRONG TO SEVERE, WITH HIGH  
CAPE AND MARGINAL SHEAR (NEAR 20 KNOTS). DAMAGING WINDS WOULD BE THE  
PRIMARY THREAT IN ANY MULTICELLULAR CLUSTERS THAT CAN OBTAIN AN  
ORGANIZED COLD POOL. AREAS THAT WOULD BE THREATENED WILL OF  
COURSE BE DETERMINED BY THE TIMING OF THE COLD FRONT AND WHAT  
HAPPENS OVERNIGHT SATURDAY NIGHT IN CASE AN EFFECTIVE FRONT  
DEVELOPS FURTHER TO THE SOUTH. AT THIS JUNCTURE, THE BEST GUESS  
ON THE AREAL EXTENT OF THE POSSIBLE STRONG TO SEVERE STORMS WITHIN  
THE CWA WOULD BE ACROSS THE SOUTHEASTERN HALF OF THE AREA.  
 
LONG ADVERTISED MAJOR PATTERN CHANGE APPEARS RIGHT ON TRACK AS A  
STRONG LONGWAVE TROUGH AMPLIFIES ACROSS THE EASTERN HALF OF THE  
CONUS. MUCH COOLER AND LESS HUMID AIR IS IN STORE FOR NEXT WEEK,  
WITH THE COOLEST TEMPERATURES EARLY IN THE WEEK BEFORE SOME  
MODERATION OCCURS. TEMPERATURES MONDAY/TUESDAY SHOULD BE NEARLY 10  
DEGREES BELOW NORMAL FOR MID/LATE JULY AND WILL FEEL NEARLY 30  
DEGREES COOLER WHEN THE HUMIDITY IS FACTORED IN COMPARED TO THE  
ONGOING HEAT WAVE.  
 
GOSSELIN  
 

 
   
AVIATION
 
(FOR THE 18Z TAFS THROUGH 18Z SATURDAY AFTERNOON)  
ISSUED AT 1151 AM CDT FRI JUL 19 2019  
 
DRY/VFR CONDITIONS ARE FORECAST THROUGH SATURDAY MORNING UNDER A  
CLEAR SKY. WEST/SOUTHWEST WINDS MAY GUST TO AROUND 20 KNOTS  
THROUGH EARLY THIS AFTERNOON AT KCOU/KUIN/KSTL, BUT SHOULD SUBSIDE  
AND BACK MORE TO THE SOUTH OVERNIGHT TONIGHT.  
 
SPECIFICS FOR KSTL:  
 
DRY/VFR THROUGH SATURDAY AFTERNOON UNDER A CLEAR OR MOSTLY CLEAR  
SKY. WEST/SOUTHWEST WINDS MAY GUST TO AROUND 20 KNOTS THROUGH  
EARLY THIS AFTERNOON BEFORE THEY SUBSIDE AND BACK MORE TO THE  
SOUTH. THIS PATTERN SHOULD LARGELY REPEAT ON SATURDAY, WITH WINDS  
VEERING TO THE SOUTHWEST OR WEST/SOUTHWEST DURING THE MORNING  
BEFORE BACKING ONCE AGAIN TO THE SOUTH SATURDAY AFTERNOON.  
 
 
GOSSELIN  
 

 
   
LSX WATCHES/WARNINGS/ADVISORIES
 
 
MO...EXCESSIVE HEAT WARNING UNTIL 8 PM CDT SATURDAY FOR AUDRAIN MO-  
BOONE MO-CALLAWAY MO-COLE MO-CRAWFORD MO-FRANKLIN MO-  
GASCONADE MO-JEFFERSON MO-KNOX MO-LEWIS MO-LINCOLN MO-  
MARION MO-MONITEAU MO-MONROE MO-MONTGOMERY MO-OSAGE MO-PIKE  
MO-RALLS MO-SAINT CHARLES MO-SAINT FRANCOIS MO-SAINT LOUIS  
CITY MO-SAINT LOUIS MO-SAINTE GENEVIEVE MO-SHELBY MO-WARREN  
MO-WASHINGTON MO.  
 
HEAT ADVISORY UNTIL 8 PM CDT SATURDAY FOR IRON MO-MADISON MO-  
REYNOLDS MO.  
 
IL...EXCESSIVE HEAT WARNING UNTIL 8 PM CDT SATURDAY FOR ADAMS IL-BOND  
IL-BROWN IL-CALHOUN IL-CLINTON IL-FAYETTE IL-GREENE IL-  
JERSEY IL-MACOUPIN IL-MADISON IL-MARION IL-MONROE IL-  
MONTGOMERY IL-PIKE IL-RANDOLPH IL-SAINT CLAIR IL-WASHINGTON  
IL.  
 

 
 

 
 
WFO LSX  
 
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