138  
FXUS63 KLSX 202320  
AFDLSX  
 
AREA FORECAST DISCUSSION...UPDATED AVIATION  
NATIONAL WEATHER SERVICE SAINT LOUIS MO  
620 PM CDT FRI APR 20 2018  
   
SHORT TERM
 
(THROUGH LATE SATURDAY AFTERNOON)  
ISSUED AT 243 PM CDT FRI APR 20 2018  
 
AFTER AN UNSEASONABLY COLD AND FROSTY EARLY MORNING, TEMPERATURES  
HAVE QUICKLY WARMED INTO THE LOWER 60S ACROSS MUCH OF THE REGION.  
THIS RAPID WARMING WAS DUE TO PLENTY OF SOLAR INSOLATION ALONG  
WITH A VERY DRY ATMOSPHERE WITH VERY LOW RELATIVE HUMIDITY. LOWS  
TONIGHT WILL BE WARMER THAN THE PREVIOUS NIGHT, ALBEIT STILL A  
LITTLE BELOW NORMAL. THE CLOUD COVER WILL INCREASE ON SATURDAY  
WELL AHEAD OF AN UPPER LEVEL LOW AND ASSOCIATED SURFACE LOW OVER  
THE CENTRAL PLAINS, BUT IT APPEARS THAT ANY PRECIPITATION WILL  
REMAIN WEST OF THE FORECAST AREA WITH THE LOWER LEVELS OF THE  
ATMOSPHERE STILL RELATIVELY DRY. EVEN THOUGH THERE WILL BE MORE  
CLOUD COVER ON SATURDAY, HIGH TEMPERATURES SHOULD BE SIMILAR TO  
FRIDAY.  
 
GKS  
   
LONG TERM
 
(SATURDAY NIGHT THROUGH NEXT FRIDAY)  
ISSUED AT 243 PM CDT FRI APR 20 2018  
 
THE UPPER LEVEL LOW AND ASSOCIATED SURFACE LOW WILL DROP  
SOUTHEASTWARD THROUGH THE SOUTHERN PLAINS AND PASS WELL SOUTH OF  
THE FORECAST AREA ON SUNDAY, MOVING THROUGH AR WITH SHOWERS MOVING  
INTO SOUTHEAST MO SATURDAY NIGHT AND INTO SOUTHWEST IL ON SUNDAY.  
THE NORTHERN FRINGES OF THE PRECIPITATION SHIELD WILL MOVE  
THROUGH THE INTERSTATE 70 CORRIDOR, ALTHOUGH THE BETTER QPF WILL  
STILL BE CONFINED TO SOUTHEAST MO AND SOUTHWEST IL. THERE IS STILL  
SOME UNCERTAINTY AS TO HOW QUICKLY THE UPPER LEVEL LOW WILL  
DEPART OUR REGION, BUT WITH THE TYPICAL SLOW NATURE OF THESE  
WEATHER SYSTEMS SHOWERS WILL LIKELY LINGER ACROSS SOUTHEAST MO AND  
SOUTHWEST IL SUNDAY NIGHT AND MONDAY. THERE SHOULD BE A BREAK IN  
THE THREAT FOR RAIN MONDAY NIGHT AND TUESDAY, BUT THEN A NORTHERN  
STREAM UPPER LEVEL TROUGH AND ASSOCIATED COLD FRONT WILL DROP  
SOUTHEASTWARD THROUGH THE FORECAST AREA WITH SHOWERS TUESDAY NIGHT  
AND WEDNESDAY. THE OPERATIONAL GFS MODEL IS A LITTLE STRONGER AND  
QUICKER WITH THE PROGRESSION OF THE UPPER LEVEL TROUGH AND COLD  
FRONT COMPARED TO THE SLOWER AND WEAKER SOLUTION OF THE ECMWF. THE  
MODELS THEN BRING A DEEPENING UPPER LEVEL TROUGH AND ANOTHER COLD  
FRONT THROUGH OUR AREA WITH SHOWERS THURSDAY NIGHT INTO FRIDAY.  
THIS UPPER LEVEL TROUGHING AND SUCCESSIVE COLD FRONTS WILL KEEP  
THE TEMPERATURES FROM GETTING TOO WARM WITH THE TENDENCY TO  
REMAIN AT OR AT LEAST SLIGHTLY BELOW NORMAL FOR LATE APRIL.  
 
GKS  
 

 
   
AVIATION
 
(FOR THE 00Z TAFS THROUGH 00Z SATURDAY EVENING)  
ISSUED AT 614 PM CDT FRI APR 20 2018  
 
VFR AND DRY THRU THE TAF PERIOD. WINDS, ELY TO ESELY, WILL  
DIMINISH SLIGHTLY WITH SUNSET. THESE WINDS WILL PICK UP AGAIN MID  
SAT MORNING. WIND DIRECTION WILL REMAIN ELY TO ESELY.  
 
TILLY  
 

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

 
 

 
 
WFO LSX  
 
CLICK HERE TO GO TO PREVIOUS BULLETINS.

The Nexlab MO Page
The Nexlab IL Page Main Text Page