442  
FXUS63 KLSX 231130 AAB  
AFDLSX  
 
AREA FORECAST DISCUSSION...UPDATED  
NATIONAL WEATHER SERVICE SAINT LOUIS MO  
630 AM CDT SUN APR 23 2017  
   
SHORT TERM
 
(THROUGH LATE TONIGHT)  
ISSUED AT 315 AM CDT SUN APR 23 2017  
 
RIDGE AXIS EXTENDING ACROSS NORTH CENTRAL KANSAS INTO CENTRAL IOWA  
WILL DRIFT SOUTHEAST INTO THE AREA TODAY. NORTH-NORTHEAST FLOW WILL  
PREVAIL AHEAD OF THE RIDGE CONTINUING TO PROVIDE WEAK COLD  
ADVECTION. REGARDLESS...FULL SUNSHINE AND AND STRONG LATE  
APRIL INSOLATION WILL WARM OUR EARLY MORNING LOWS FROM THE LOW TO  
MID 40S UP INTO THE UPPER 60S AND LOWER 70S THIS AFTERNOON. THE  
RIDGE WILL CONTINUE DRIFTING EAST TONIGHT. WIND WILL TURN AROUND TO  
THE SOUTH OVER CENTRAL AND NORTHEAST MISSOURI AS WELL AS WEST  
CENTRAL ILLINOIS TONIGHT. LOWS TONIGHT WILL BE A LITTLE TRICKY  
DUE TO THE WIND SHIFT. AFOREMENTIONED AREAS MAY SEE LOWS AROUND  
MIDNIGHT WITH STEADY OR SLOWLY RISING TEMPERATURES TOWARD MORNING  
WHILE THE REMAINDER OF THE AREA MAY HAVE A MORE NORMAL DIURNAL  
TEMPERATURE CURVE. IT DOES LOOK LIKE LOWS WILL BE A BIT WARMER ON  
MONDAY MORNING ACROSS THE AREA DUE TO THE WARMER START TO THE  
EVENING. GENERALLY STUCK PRETTY CLOSE TO MOS GUIDANCE...THOUGH I  
DID KNOCK A FEW DEGREES OFF TEMPERATURES IN RIVER VALLEYS DUE TO  
LIGHT WIND AND CLEAR SKY RESULTING IN EXCELLENT RADIATIONAL COOLING  
CONDITIONS.  
 
CARNEY  
   
LONG TERM
 
(MONDAY THROUGH SATURDAY)  
ISSUED AT 315 AM CDT SUN APR 23 2017  
 
CLOSED UPPER LOW THAT WILL BE OVER THE SOUTHEAST CONUS EARLY ON  
MONDAY MORNING WILL MOVE OFFSHORE AND UP THE EAST COAST BY MIDWEEK.  
IN THE MEANTIME, WHAT WILL START OUT AS QUASI-ZONAL FLOW OVER THE  
WESTERN TWO-THIRDS OF COUNTRY WILL AMPLIFY AS A TROUGH ENTERS THE  
WESTERN CONUS ON MONDAY AND DEEPENS INTO A LONGWAVE OVER THE CENTRAL  
PLAINS BY WEDNESDAY. AHEAD OF THIS TROUGH, MONDAY AND TUESDAY STILL  
LOOK WARM AND DRY AS THE UPPER FLOW TURNS OUT OF THE SOUTHWEST AND  
850MB TEMPERATURES CLIMB INTO THE 10-15C RANGE. THERE IS RELATIVELY  
GOOD AGREEMENT BETWEEN THE GFS/ECMWF/CANADIAN THAT A COLD FRONT WILL  
MOVE THROUGH MO/IL AHEAD OF THIS TROUGH ON WEDNESDAY. GFS AND ECMWF  
ARE SHOWING ENOUGH INSTABILITY AND SHEAR FOR A FEW ORGANIZED  
THUNDERSTORMS ON WEDNESDAY AS THE FRONT MOVES THROUGH THE AREA.  
 
THE FRONT WILL MOVE EAST OF THE AREA BY WEDNESDAY NIGHT AND A  
SURFACE HIGH WILL MOVE ACROSS THE AREA ON THURSDAY. TEMPERATURES  
WILL BE COOLER WITH 850MB TEMPERATURES ONLY AROUND 5C WITH A SLIGHT  
CHANCE OF SHOWERS AND THUNDERSTORMS AS BOTH GFS/ECMWF SHOW A WEAK  
SHORTWAVE MOVING ACROSS THE MIDWEST. BETTER CHANCE OF SHOWERS AND  
THUNDERSTORMS WILL COME BY NEXT FRIDAY AND SATURDAY WHEN A DEEPER  
CLOSED LOW WILL SET UP OVER THE SOUTHWESTERN CONUS. THIS WILL CAUSE  
LOW PRESSURE TO DEEPEN OVER THE PLAINS AND A WARM FRONT TO MOVE  
NORTH INTO MISSOURI AND ILLINOIS BY FRIDAY NIGHT. SHOWERS AND  
THUNDERSTORMS WILL START OVER THE MISSOURI AND ILLINOIS AHEAD OF THE  
WARM FRONT ON THURSDAY NIGHT AND FRIDAY AS STRONG LOW LEVEL MOISTURE  
CONVERGENCE SETS UP ON THE NOSE OF A LOW LEVEL JET. THE GFS/ECMWF  
SHOWS THE WARM FRONT MOVING INTO THE REGION BY NEXT SATURDAY WITH  
THE CHANCE OF THUNDERSTORMS CONTINUING.  
 
BRITT  
 

 
   
AVIATION
 
(FOR THE 12Z TAFS THROUGH 12Z MONDAY MORNING)  
ISSUED AT 625 AM CDT SUN APR 23 2017  
 
HIGH PRESSURE WILL CONTROL THE WEATHER TODAY AND TONIGHT. NORTH-  
NORTHEAST FLOW AND VFR FLIGHT CONDITIONS WILL PREVAIL TODAY WITH  
LIGHT AND VARIABLE WIND TONIGHT...TURNING TO THE SOUTHEAST LATE  
TONIGHT OVER CENTRAL AND NORTHEAST MISSOURI AS WELL AS WEST  
CENTRAL ILLINOIS AS THE RIDGE AXIS MOVES THROUGH.  
 
SPECIFICS FOR KSTL:  
 
VFR FLIGHT CONDITIONS AND NORTH-NORTHEAST FLOW WILL PREVAIL AT  
LAMBERT THROUGH THE EVENING. THERE MAY BE AN OCCASIONAL WIND GUST  
TO AROUND 15KTS THIS MORNING, BUT GUSTS SHOULD SUBSIDE BY EARLY TO  
MID AFTERNOON. VFR CONDITIONS WILL CONTINUE TONIGHT...AND THE WIND  
WILL BECOME LIGHT AND VARIABLE, THEN TURN TO THE SOUTHEAST ON  
MONDAY MORNING AS THE RIDGE AXIS MOVES EAST OF THE TERMINAL.  
 
CARNEY  
 

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

 
 

 
 
WFO LSX  
 
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