030  
FXUS63 KLSX 170106  
AFDLSX  
 
AREA FORECAST DISCUSSION...UPDATED  
NATIONAL WEATHER SERVICE SAINT LOUIS MO  
806 PM CDT MON OCT 16 2017  
   
UPDATE
 
 
ISSUED AT 742 PM CDT MON OCT 16 2017  
 
THE ELONGATED SURFACE HIGH PRESSURE CENTERED IN SOUTHWESTERN  
MISSOURI WILL SLIDE EASTWARD TONIGHT AND WILL BE IN CONTROL OVER  
THE REGION. A FEW HIGH CLOUDS ARE POSSIBLE OVERNIGHT OVER PARTS OF  
CENTRAL MISSOURI AND WESTERN ILLINOIS. A COMBINATION OF LIGHT  
WINDS AND GOOD RADIATIONAL COOLING WILL LEAD TO SOME STEAM FOG  
OVER THE RIVERS TONIGHT PARTICULARLY IN SOUTHEAST MISSOURI AND  
SOUTHWESTERN ILLINOIS. THERE ALSO COULD BE SOME PATCHY FROST  
OVERNIGHT, PARTICULARLY IN PARTS OF SOUTHEAST MISSOURI AND  
SOUTHWESTERN ILLINOIS. THE WINDS WILL LIKELY BE LIGHT OR CALM  
ALONG WITH THE DEVELOPMENT OF A STRONG SURFACE BASED INVERSION  
WHICH WILL ALLOW TEMPERATURES TO FALL INTO THE MID TO UPPER 30S  
OVER THOSE AREAS.  
 
KELLY  
 

 
   
SHORT TERM
 
(THROUGH LATE TUESDAY AFTERNOON)  
ISSUED AT 309 PM CDT MON OCT 16 2017  
 
THE ELONGATED SURFACE HIGH CURRENTLY CENTERED NEAR JOPLIN WILL  
SLIDE EASTWARD TONIGHT AND WILL BE THE CONTROLLING WEATHER  
FEATURE. AS IS TYPICAL WITH RETREATING SURFACE HIGHS IN THIS  
SCENARIO, THE SURFACE WINDS WILL ATTAIN A LIGHT SOUTHERLY  
COMPONENT IN CENTRAL AND NORTHEAST MO THIS EVENING. THIS WIND  
FLOW ALONG WITH WEAK LOW LEVEL WAA AND AN INCREASE IN HIGH CLOUDS  
LATE WILL BE SOMEWHAT BALANCED BY LOW SURFACE DEW POINTS LEADING  
TO MINS IN THE LOWER TO MID 40S. ELSEWHERE AND MORE SPECIFICALLY  
ACROSS SOUTHEAST MO AND SOUTHERN IL, THE WIND WILL BE LIGHT TO  
CALM, AND THERE SHOULD BE DECOUPLING AND THE DEVELOPMENT OF A  
STRONG SURFACE BASED INVERSION. THIS SHOULD ALLOW FOR MOST AREAS  
TO FALL NICELY AND IT WILL BE A COOL NIGHT WITH MINS IN THE MID-  
UPPER 30S. ATTENDANT WITH THESE COOL TEMPS ACROSS SOUTHEAST  
MO/SOUTHERN IL WILL BE FOG IN THE RIVER VALLEYS AND EVEN SOME  
PATCHY FROST. NOTE SOME PATCHY FROST WAS REPORTED THIS MORNING.  
 
TEMPS SHOULD MODERATE NICELY ON TUESDAY. THE PATTERN ALOFT WILL BE  
SOMEWHAT PROGRESSIVE AND FLATTENING IN GENERAL WITH THE EASTERN  
U.S. TROF SCOOTING INTO THE WESTERN ATLANTIC. THE LOWER TROPOSPHERIC  
HIGH WILL CONTINUE TO SLOWLY RETREAT WITH SOUTH-SOUTHWESTERLY LOW  
LEVEL FLOW AND PRONOUNCED WAA. THE DRY AIR MASS SHOULD RESPOND  
NICELY WITH HIGHS IN THE UPPER 60S - LOWER 70S.  
 
GLASS  
   
LONG TERM
 
(TUESDAY NIGHT THROUGH NEXT MONDAY)  
ISSUED AT 309 PM CDT MON OCT 16 2017  
 
THE REMAINDER OF THE WEAK SHOULD BE TRANQUIL WITH MODERATING,  
ABOVE AVERAGE TEMPERATURES. THE FLOW ALOFT GENERALLY REMAINS  
QUASI-ZONAL WITH PERIODIC BOUTS OF HIGH CLOUDS. THE LOW LEVEL WAA  
REGIME REMAINS INTACT WITH SOUTH-SOUTHWEST LOW LEVEL FLOW. A COLD  
FRONT WILL ENCROACH INTO THE NORTHERN CWA ON THURSDAY MORNING,  
BUT ITS PRESENCE WILL BE SHORT-LIVED AS IT BOUNCES NORTH AND  
UNDERGOES FRONTOLYSIS WITH HEIGHTS ON THE RISE ALOFT.  
 
THESE HEIGHT RISES ALOFT WILL BE PART OF SIGNIFICANT  
AMPLIFICATION/CHANGE IN THE LARGE SCALE PATTERN BEGINNING DURING  
THE LATER PART OF THE WEEK AND CONTINUING THROUGH THE WEEKEND.  
INITIALLY AN UPPER TROF WILL DEEPEN ACROSS THE WESTERN U.S. WITH  
AN UPPER RIDGE BUILDING FROM THE DIXIE REGION INTO THE OH VALLEY.  
THIS WILL BRING A RETURN OF SOUTHWEST FLOW ALOFT TO THE MID MS  
VALLEY AND STRENGTHENING LOW LEVEL SOUTH-SOUTHWEST FLOW ON FRIDAY.  
THE PRESENCE OF THE EXPANSIVE SURFACE/LOW LEVEL ANTICYCLONE IN THE  
EASTERN U.S. WILL SLOW THE RETURN OF MOISTURE RETURN DESPITE THIS  
FLOW REGIME. PRESENT INDICATIONS ARE THAT THE COMBO OF THE MOBILE  
WESTERN UPPER TROF AND EASTWARD PROGESSION OF THE ANTICYCLONE  
WILL ALLOW FOR MOISTURE RETURN INTO THE AREA BEGINNING ON  
SATURDAY, INCREASING SATURDAY NIGHT INTO SUNDAY AHEAD OF AN  
ADVANCING COLD FRONT. STEEP LAPSE RATES WILL BE PRESENT THANKS TO  
THE SOUTHWEST FLOW AHEAD OF THE PROGRESSIVE UPPER TROF, CONTRIBUTING  
TO SUFFICIENT INSTABILITY FOR SHOWERS/THUNDERSTORMS WITH THE COLD  
FRONT AND AHEAD IT.  
 
GLASS  
 

 
   
AVIATION
 
(FOR THE 00Z TAFS THROUGH 00Z TUESDAY EVENING)  
ISSUED AT 552 PM CDT MON OCT 16 2017  
 
VFR FLIGHT CONDITIONS EXPECTED THROUGH TUESDAY EVENING. AN AREA OF  
HIGH PRESSURE WILL SLIDE SOUTH OF THE AREA WITH A FEW HIGH  
CLOUDS POSSIBLE TONIGHT OVER CENTRAL MISSOURI AND WESTERN  
ILLINOIS. A COMBINATION OF LIGHT WINDS AND GOOD RADIATIONAL  
COOLING WILL LIKELY LEAD TO SOME STEAM FOG TONIGHT PARTICULARLY  
AT KSUS AND KCPS. THE TIMING OF THE STEAM FOG DEVELOPMENT WILL  
ROUGHLY BE IN THE 9Z TO 15Z TIME FRAME WITH VISIBILITIES OF 1 TO  
2SM POSSIBLE WITHIN THE VICINITY OF RIVERS. WINDS WILL PICKUP BY  
TUESDAY MORNING AND BE OUT OF THE SOUTH.  
 
SPECIFICS FOR KSTL: VFR FLIGHT CONDITIONS ARE EXPECTED THROUGH  
TUESDAY EVENING. A FEW HIGH CLOUDS ARE POSSIBLE LATE TONIGHT INTO  
EARLY TUESDAY MORNING OVER THE TERMINAL. WINDS WILL BE LIGHT  
OVERNIGHT, BUT PICK UP TUESDAY MORNING OUT OF THE SOUTH.  
 
KELLY  
 

 
   
PRELIMINARY POINT TEMPS/POPS
 
 
SAINT LOUIS 43 72 48 75 / 0 0 0 0  
QUINCY 44 70 47 72 / 0 0 0 0  
COLUMBIA 44 72 45 74 / 0 0 0 0  
JEFFERSON CITY 42 72 45 75 / 0 0 0 0  
SALEM 38 70 45 73 / 0 0 0 0  
FARMINGTON 35 69 43 73 / 0 0 0 0  
 

 
   
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