878  
FXUS63 KLSX 291725  
AFDLSX  
 
AREA FORECAST DISCUSSION...UPDATED AVIATION  
NATIONAL WEATHER SERVICE SAINT LOUIS MO  
1225 PM CDT THU JUL 29 2021  
   
SHORT TERM
 
(THROUGH LATE TONIGHT)  
ISSUED AT 332 AM CDT THU JUL 29 2021  
 
THE STRONG UPPER LEVEL RIDGE REMAINS IN PLACE ACROSS THE WESTERN TWO  
THIRDS OF THE CONUS WITH A SHORTWAVE MOVING THROUGH THE NW FLOW OVER  
THE GREAT LAKES. AT THE SURFACE, THE CENTER OF A BROAD HIGH IS  
SITUATED NEAR THE MISSOURI BOOTHEEL. TO OUR NORTH, THERE IS A LOW  
CENTERED NEAR THE WI/MN/IA BORDERS ASSOCIATED WITH THE SHORTWAVE,  
A COLD FRONT EXTENDING TO THE WSW OF THE LOW, AND A RATHER ROBUST  
QLCS MOVING SOUTH THROUGH NORTHERN ILLINOIS.  
 
THE QLCS HAS FINALLY BEGUN TO WEAKEN, BUT IT IS MOVING IN A MUCH  
FURTHER SOUTH THAN ANY GUIDANCE ANTICIPATED. WHILE THE ODDS OF  
ANY OF THIS PRECIPITATION REACHING OUR CWA ARE LOW, WE'RE LIKELY  
GOING TO SEE QUITE A BIT OF CLOUD COVERAGE THIS MORNING, ESPECIALLY  
OVER OUR ILLINOIS COUNTIES. THESE CLOUDS WILL LIKELY LIMIT TEMPERATURES  
A BIT, BUT WSW SURFACE AND LOW LEVEL WINDS WILL CONTINUE TO ADVECT  
VERY WARM AND MOIST AIR INTO THE REGION. GIVEN A WARM START TO THE  
DAY AND DEWPOINTS IN THE 70S, HEAT ADVISORY CRITERIA (HX OVER 105)  
STILL SEEMS LIKE A SAFE BET DESPITE MORE CLOUDS THAN EXPECTED,  
ESPECIALLY ALONG AND WEST OF THE MISSISSIPPI. THEREFORE WILL BE  
KEEPING THE HEAT ADVISORY IN PLACE AS-IS.  
 
THE ABOVE COLD FRONT IS EXPECTED TO PUSH INTO THE REGION SOMETIME  
THIS EVENING AS THE UPPER RIDGE BEGINS TO BREAK DOWN. MOST OF THE  
CAMS DEVELOP AT LEAST ISOLATED/SCATTERED STORMS ALONG THE FRONT,  
WHICH SEEMS REASONABLE GIVEN THE FRONTAL FORCING AND MID/UPPER  
LEVEL HEIGHT FALLS. WHILE STORM COVERAGE MAY BE LIMITED A BIT BY  
VERY WARM TEMPS JUST ABOVE THE SURFACE, STORMS SEEM PRETTY LIKELY  
AT THIS POINT. THESE STORMS WILL DEVELOP IN A VERY UNSTABLE AND  
MODERATELY SHEARED ATMOSPHERE, WHICH MAY ALLOW A FEW STORMS TO  
BECOME STRONG TO SEVERE. HOWEVER, WITH ONLY 20-25KT 0-3KM BULK  
SHEAR, STORM ORGANIZATION AND SEVERE POTENTIAL WILL BE LIMITED,  
WITH DAMAGING WINDS AND LARGE HAIL BEING THE INITIAL THREATS. AS  
THE FRONT BEGINS TO STALL OVERNIGHT, WE MAY SEE SOME STORM  
TRAINING. MOST STORMS SHOULD BE VERY EFFICIENT RAINFALL PRODUCERS  
GIVEN PRECIPITABLE WATER NEAR 2" AND WARM CLOUD DEPTHS NEAR 4KM.  
IF ANY AREAS ARE HIT BY MULTIPLE ROUNDS OF STORMS, SOME FLOODING  
MAY BE POSSIBLE.  
 
BSH  
   
LONG TERM
 
(FRIDAY THROUGH WEDNESDAY)  
ISSUED AT 332 AM CDT THU JUL 29 2021  
 
THE UPPER RIDGE WILL FINALLY BREAK DOWN AS WE MOVE INTO THE WEEKEND  
THANKS TO AN AMPLIFYING TROUGH OVER THE EASTERN CONUS. A SERIES  
OF SHORTWAVES WILL BRING REINFORCING SHOTS OF SEASONABLY COOL AIR  
INTO THE REGION, KEEPING THE FRONT LAID OUT SOMEWHERE IN THE  
VICINITY OF THE MIDDLE MISSISSIPPI/LOWER MISSOURI RIVER VALLIES.  
WHILE UNCERTAINTY REMAINS REGARDING FRONTAL POSITIONING, THE  
STALLED/SLOW MOVING FRONT MAY RESULT IN MULTIPLE ROUNDS OF SHOWERS  
AND STORMS FOR SOME AREAS. WHILE THE LATEST GUIDANCE IS  
HIGHLIGHTING SATURDAY WITH THE HIGHEST ODDS FOR PRECIPITATION,  
THERE IS AT LEAST A CHANCE OF PRECIPITATION SOMEWHERE IN THE CWA  
FROM FRIDAY THROUGH SATURDAY. ANY STORMS THAT DO DEVELOP WILL ALSO  
LIKELY BE RATHER EFFICIENT RAINFALL PRODUCERS GIVEN AMPLE PRECIPITABLE  
WATER ALONG AND SOUTH OF THE FRONT. THIS AGAIN MAY RESULT IN AT  
LEAST ISOLATED FLASH FLOODING IN AREAS THAT DO SEE MULTIPLE ROUNDS  
OF STORMS.  
 
THE UPPER TROUGH TO OUR EAST WILL CONTINUE TO DEEPEN INTO NEXT WEEK,  
EVENTUALLY PUSHING THE FRONT OUT OF THE REGION. THIS WILL PUT AN  
END TO OUR RAINFALL CHANCES AND RESULT IN A CONTINUED PERIOD OF  
COOLER CONDITIONS THROUGH MIDWEEK.  
 
BSH  
 

 
   
AVIATION
 
(FOR THE 18Z TAFS THROUGH 18Z FRIDAY AFTERNOON)  
ISSUED AT 1224 PM CDT THU JUL 29 2021  
 
THE MAIN FOCUS FOR IMPACTS THIS PERIOD WILL BE A SOUTHWARD MOVING  
COLD FRONT AND ASSOCIATED STORM POTENTIAL. THIS FRONT IS CURRENTLY  
ACROSS SOUTHERN IOWA AND NORTHERN MISSOURI, AND IS EXPECTED TO MOVE  
OVER THE KUIN TERMINAL LATER THIS AFTERNOON. AT THAT TIME, STORMS  
WILL FORM ALONG THE FRONT, BUT COVERAGE IS EXPECTED TO BE ISOLATED  
TO SCATTERED, SO CONFIDENCE IS NOT HIGH ENOUGH TO HAVE DIRECT IMPACT  
TO THE TERMINAL MENTIONED IN THE TAF AT THE MOMENT. AS THE FRONT AND  
ASSOCIATED STORMS MOVE FURTHER SOUTH THIS EVENING, STORM COVERAGE IS  
EXPECTED TO LESSEN, DECREASING CONFIDENCE FURTHER IN DIRECT IMPACTS  
TO THE REMAINING LOCAL TERMINALS, INCLUDING KSTL. FOR ALL LOCAL  
TERMINALS, STORMS THAT DO DIRECTLY IMPACT TERMINALS WILL BE CAPABLE  
OF HEAVY RAINFALL AND GUSTY WINDS, SO SUB-VFR FLIGHT CONDITIONS ARE  
POSSIBLE. THE FRONT IS ANTICIPATED TO CLEAR ALL LOCAL TERMINALS BY  
TOMORROW MORNING EXCEPT KCOU AND KJEF WHERE THE FRONT MAY LINGER, SO  
I'VE LEFT VCSH IN THE TAF FOR NOW. WITH THE FRONT'S PASSAGE, WINDS  
WILL SHIFT TO OUT OF THE NORTH AND REMAIN LIGHT.  
 
ELMORE  
 

 
   
PRELIMINARY POINT TEMPS/POPS
 
 
SAINT LOUIS 98 74 86 67 / 5 40 30 40  
QUINCY 93 71 82 64 / 40 50 20 70  
COLUMBIA 96 74 87 70 / 0 20 30 40  
JEFFERSON CITY 97 76 89 71 / 0 20 30 30  
SALEM 97 70 84 63 / 20 40 10 20  
FARMINGTON 97 72 88 67 / 0 20 40 10  
 

 
   
LSX WATCHES/WARNINGS/ADVISORIES
 
 
MO...HEAT ADVISORY UNTIL 9 PM CDT THIS EVENING FOR AUDRAIN MO-BOONE  
MO-CALLAWAY MO-COLE MO-CRAWFORD MO-FRANKLIN MO-GASCONADE MO-  
IRON MO-JEFFERSON MO-KNOX MO-LEWIS MO-LINCOLN MO-MADISON MO-  
MARION MO-MONITEAU MO-MONROE MO-MONTGOMERY MO-OSAGE MO-PIKE  
MO-RALLS MO-REYNOLDS MO-SAINT CHARLES MO-SAINT FRANCOIS MO-  
SAINT LOUIS CITY MO-SAINT LOUIS MO-SAINTE GENEVIEVE MO-  
SHELBY MO-WARREN MO-WASHINGTON MO.  
 
IL...HEAT ADVISORY UNTIL 9 PM CDT THIS EVENING 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-WASHINGTON IL.  
 

 
 

 
 
WFO LSX  
 
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