638  
FXUS63 KLSX 240459  
AFDLSX  
 
AREA FORECAST DISCUSSION...UPDATED AVIATION  
NATIONAL WEATHER SERVICE SAINT LOUIS MO  
1159 PM CDT SAT SEP 23 2017  
   
SHORT TERM
 
(THROUGH LATE SUNDAY AFTERNOON)  
ISSUED AT 307 PM CDT SAT SEP 23 2017  
 
EARLY THIS AFTERNOON, AN UPPER LEVEL RIDGE REMAINS DOMINANT OVER OUR  
REGION. UNDER THIS RIDGE, A COUPLE "AIRMASS" SHOWERS HAVE DEVELOPED  
BUT HAVE ALSO BEEN VERY SHORT LIVED. A LARGE SURFACE HIGH PRESSURE  
IS CENTERED OVER THE EASTERN GREAT LAKES, A BIT FURTHER NORTH THAN  
24HRS AGO, AND HAS RESULTED IN A MORE EASTERLY FLOW OVER OUR REGION  
VERSUS SOUTHERLY LIKE IT WAS YESTERDAY. THIS MORE EASTERLY FLOW HAS  
RESULTED IN TEMPS A DEG OR TWO COOLER THAN 24HRS AGO. A HEALTHY  
DIURNAL CUMULUS CLOUD FIELD WAS OVER MUCH OF OUR REGION. AS OF THIS  
WRITING, NO RECORD TEMPS HAVE BEEN TIED.  
 
SOME "AIRMASS" SHOWERS OR STORMS COULD STILL DEVELOP THRU SUNSET,  
PARTICULARLY IN NORTHEAST, CENTRAL, OR SOUTHEAST MO. OTHERWISE,  
LOOK FOR THE DIURNAL CUMULUS CLOUD FIELD TO DISSIPATE AROUND SUNSET  
WITH CLEAR SKIES OVERNIGHT. PERSISTENCE WILL BE HARD TO BEAT FOR  
MIN TEMPS OVERNIGHT, WITH MID TO UPPER 60S FOR MOST AREAS, AND  
LOW 70S FOR URBANIZED AREAS OF STL METRO.  
 
THE UPPER RIDGE'S INFLUENCE LOOKS TO FINALLY WEAKEN ON SUNDAY AS IT  
MOVES AWAY FURTHER TO THE EAST, WITH THE MODELS EVEN SHOWING A WEAK  
UPPER LEVEL DISTURBANCE ROTATING AROUND THE RIDGE INTO SOUTHERN IL  
BY SUNDAY AFTERNOON. ALREADY HAVE LOW POPS GOING FOR SOUTHEAST AND  
CENTRAL MO AGAIN BUT THIS MAY NEED TO BE EXPANDED IN COVERAGE IN  
SUBSEQUENT FORECAST PACKAGES.  
 
WITH THE DEPARTURE OF THE UPPER RIDGE, MAX TEMPS SHOULD CONTINUE TO  
TAKE MORE OF A HIT AND EDGED THEM DOWN ANOTHER DEG OR TWO FROM  
PERSISTENCE.  
 
TES  
   
LONG TERM
 
(SUNDAY NIGHT THROUGH NEXT SATURDAY)  
ISSUED AT 307 PM CDT SAT SEP 23 2017  
 
A VERY AMPLIFIED UPPER AIR PATTERN WILL BEGIN THE WORK WEEK WITH A  
DEEP TROUGH OF LOW PRESSURE ACROSS THE ROCKIES AND A STRONG RIDGE OF  
HIGH PRESSURE ACROSS THE NORTHEAST CONUS. DEEP SOUTH/SOUTHWESTERLY  
FLOW OVERHEAD WILL ENSURE UNSEASONABLY WARM TEMPERATURES CONTINUING  
UNTIL THE PASSAGE OF A COLD FRONT TUESDAY AFTERNOON.  
 
TROF OF LOW PRESSURE ATTEMPTS TO PUSH EAST BY MIDWEEK BUT REALLY  
GETS SHUNTED TO THE NORTH INTO THE UPPER MIDWEST WITH THE OVERALL  
FLOW BECOMING MORE ZONAL ACROSS THE CENTER OF THE CONUS. THE  
ACCOMPANYING SURFACE COLD FRONT IS STILL EXPECTED TO MOVE THROUGH  
THE CWA, BUT WITH THE BEST DYNAMICS STAYING WELL NORTH AND LIMITED  
LOW LEVEL MOISTURE, POPS CONTINUE TO SLOWLY DISSAPEAR IN THE  
EXTENDED. AT LEAST THE FRONT SHOULD KNOCK TEMPERATURES BACK TO  
NORMAL WITH HIGHS IN THE 70S.  
 
CVKING  

 
   
AVIATION
 
(FOR THE 06Z TAFS THROUGH 06Z SUNDAY NIGHT)  
ISSUED AT 1137 PM CDT SAT SEP 23 2017  
 
CLEAR SKIES AND LIGHT EAST WINDS TO PREVAIL TONIGHT, THEN WILL SEE  
SCATTERED DIURNAL CU DEVELOP BY MIDDAY TODAY WITH LIGHT SOUTHEAST  
WINDS.  
 
SPECIFICS FOR KSTL:  
CLEAR SKIES AND LIGHT EAST WINDS TO PREVAIL TONIGHT, THEN WILL SEE  
SCATTERED DIURNAL CU DEVELOP BY 18Z SUNDAY WITH LIGHT SOUTHEAST  
WINDS.  
 
BYRD  

 
   
CLIMATE
 
 
RECORD MAX TEMPERATURES THROUGH SATURDAY  
 
KSTL KCOU KUIN  
SEPT 23 94 (1891) 94 (2007) 95 (1937)  
SEPT 24 94 (1891) 95 (1891) 94 (1935)  
 
RECORD HIGH MIN TEMPERATURES THROUGH SATURDAY  
 
KSTL KCOU KUIN  
SEPT 22 73 (2005) 71 (2005) 71 (1930)  
SEPT 23 73 (1884) 73 (1937) 73 (1937)  
 

 
   
LSX WATCHES/WARNINGS/ADVISORIES
 
 
MO...NONE.  
IL...NONE.  

 
 

 
 
WFO LSX  
 
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