055  
FXUS63 KLSX 230835  
AFDLSX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE SAINT LOUIS MO  
335 AM CDT SAT JUN 23 2018  
   
SHORT TERM
 
(THROUGH LATE TONIGHT)  
ISSUED AT 332 AM CDT SAT JUN 23 2018  
 
PRIMARY CONCERN FOR TODAY AND TONIGHT IS POPS. THE LOW WHICH  
BROUGHT US CLOUDS AND RAIN OVER THE PAST SEVERAL DAYS HAS MOVED EAST  
INTO THE OHIO VALLEY. NORTHWEST FLOW ALOFT IN THE WAKE OF THE LOW  
WILL BECOME MORE ZONAL TODAY AS THE DAY PROGRESSES. THIS WILL ALLOW  
A SHORTWAVE CURRENTLY OVER KANSAS TO MOVE INTO MISSOURI DURING THE  
AFTERNOON. EXPECT THE GREATEST CHANCES FOR THUNDERSTORMS TO BE  
SOUTHWEST AND SOUTH OF THE FORECAST AREA TODAY ALONG WITH THE  
GREATEST INSTABILITY. FORECAST SOUNDINGS SHOW A DECENT CAPPING  
INVERSION OVER THE AREA THIS AFTERNOON, BUT THIS SHORTWAVE MOVING  
IN FROM THE WEST COULD WEAKEN THE CAP ENOUGH FOR ISOLATED  
AFTERNOON CONVECTION TO DEVELOP. ALL SHORT RANGE GUIDANCE  
INCLUDING THE CAMS SHOW SOME EVIDENCE OF THIS WITH ISOLATED LIGHT  
QPF AND ISOLATED CONVECTION THIS AFTERNOON. SHORT RANGE GUIDANCE  
SHOWS 1000-1500 J/KG MLCAPE THIS AFTERNOON SO THERE SHOULD BE MORE  
THAN ENOUGH INSTABILITY FOR ANY UPDRAFTS THAT GO UP TO PRODUCE  
THUNDER. HAVE THEREFORE BUMPED UP POPS ACROSS THE AREA TO AROUND  
20%.  
 
THE BEST CHANCE FOR STORMS TONIGHT STILL LOOKS WELL SOUTH OF OUR  
FORECAST AREA ALONG THE AXIS OF GREATEST BAROCLINICITY. SHORT RANGE  
GUIDANCE MEMBERS DO DEVELOP A 25-30KT LOW LEVEL JET OVER ARKANSAS  
WHICH MOVES THE BAROCLINIC ZONE A BIT NORTHWARD OVERNIGHT. CAN'T  
RULE OUT A FEW STORMS POKING UP INTO SOUTHEAST MISSOURI/SOUTHERN  
ILLINOIS LATE, SO HAVE SOME 20-30 POPS TO COVER. TEMPERATURES  
SHOULD BE CLOSER TO NORMAL IN THE LOW TO MID 80S TODAY WITH  
OCCASIONAL BREAKS IN THE CLOUDS AND MUCH LESS PRECIP COVERAGE THAN  
THE PAST COUPLE OF DAYS.  
 
CARNEY  
 
   
LONG TERM
 
(SUNDAY THROUGH FRIDAY)  
ISSUED AT 332 AM CDT SAT JUN 23 2018  
 
WARMER, NEAR NORMAL TEMPERATURES CAN BE EXPECTED ON SUNDAY AS AN  
UPPER LEVEL RIDGE BUILDS OVER THE REGION. AN MCS MAY MOVE EASTWARD  
THROUGH PARTS OF THE FORECAST AREA SUNDAY NIGHT AHEAD OF AN  
APPROACHING SOUTHWEST FLOW SHORTWAVE AND ALONG AND NORTH OF A WARM  
FRONT LIFTING SLOWLY NORTH-NORTHEASTWARD INTO THE AREA. A BACKDOOR  
TYPE COLD FRONT WILL ALSO SAG SOUTH-SOUTHWESTWARD INTO PARTS OF  
NORTHEAST MO AND SOUTHERN IL BY 12Z MONDAY AS A SURFACE RIDGE BUILDS  
SOUTHWARD THROUGH THE GREAT LAKES REGION. THE CHANCE OF CONVECTION  
CONTINUES MONDAY AND MONDAY NIGHT AS A WARM FRONT LIFTS NORTH-  
NORTHEASTWARD THROUGH THE FORECAST AREA, WHILE AN UPPER LEVEL  
TROUGH/LOW MOVES EASTWARD THROUGH THE NORTHERN PLAINS. THIS UPPER  
LEVEL TROUGH/LOW WILL MOVE INTO THE GREAT LAKES REGION TUESDAY AND  
TUESDAY NIGHT AND SEND A WEAK COLD FRONT/SURFACE TROUGH  
SOUTHEASTWARD INTO THE FORECAST AREA WHICH WILL BE THE FOCUS FOR THE  
DEVELOPMENT OF SHOWERS/STORMS TUESDAY/TUESDAY NIGHT. AN UPPER LEVEL  
RIDGE WILL BUILD NORTHEASTWARD INTO THE REGION ON WEDNESDAY  
BEGINNING A PERIOD OF HOT AND HUMID CONDITIONS WITH AFTERNOON HEAT  
INDICES POSSIBLY REACHING 100-105 ACROSS PARTS OF THE FORECAST AREA.  
IT APPEARS THAT MOST OF THE CONVECTION WILL REMAIN NORTH OF THE  
FORECAST AREA, ALTHOUGH COULD NOT RULE OUT SHOWERS AND STORMS  
CLIPPING NORTHEAST MO AND WEST CENTRAL IL WEDNESDAY NIGHT THROUGH  
THURSDAY NIGHT DUE TO WEAK "RIDGE RUNNER" SHORTWAVES OVER-TOPPING  
THE UPPER LEVEL RIDGE. THE WARMEST TEMPERATURES SHOULD OCCUR  
THURSDAY AND FRIDAY WITH PERSISTENT SOUTHERLY SURFACE WINDS AND  
SOUTHWESTERLY LOW LEVEL WINDS.  
 
GKS  
 

 
   
AVIATION
 
(FOR THE 06Z TAFS THROUGH 06Z SATURDAY NIGHT)  
ISSUED AT 1139 PM CDT FRI JUN 22 2018  
 
THE POTENTIAL FOR MVFR CIGS WILL BE THE MAIN FOCUS OF THE TAF  
PERIOD. CIGS HAVE BEEN SLOWER THAN ORIGINALLY FORECAST TO FILL IN  
ACROSS THE AREA, CASTING SOME UNCERTAINTY ON HOW THE REST OF THE  
OVERNIGHT HOURS WILL PLAY OUT. HAVE BACKED OFF THE POTENTIAL FOR  
MVFR CIGS A BIT OVERNIGHT MAINLY IN THE ST. LOUIS METRO SITES, BUT  
STILL EXPECT AT LEAST SOME RESTRICTIONS LATE TONIGHT INTO SATURDAY  
MORNING. HAVE HIGHER CONFIDENCE AT UIN IN MVFR CIGS, WITH EVEN A  
BRIEF FORAY INTO IFR NOT OUT OF THE QUESTION. CAN'T COMPLETELY  
RULE OUT SOME LIGHT FOG TONIGHT AT ALL SITES AS WELL, BUT THINK  
ANY VSBY IMPACTS SHOULD BE FAIRLY SHORT-LIVED GIVEN THE WIDESPREAD  
NATURE OF THE CLOUD COVER. CONDITIONS WILL RETURN TO VFR ON  
SATURDAY, WITH GENERALLY LIGHT AND VARIABLE WINDS EXPECTED.  
 
SPECIFICS FOR KSTL:  
THE POTENTIAL FOR MVFR CIGS WILL BE THE MAIN FOCUS OF THE TAF  
PERIOD. CIGS HAVE BEEN SLOWER THAN ORIGINALLY FORECAST TO FILL IN  
OVER STL, CASTING SOME UNCERTAINTY ON HOW THE REST OF THE  
OVERNIGHT HOURS WILL PLAY OUT. HAVE BACKED OFF THE POTENTIAL FOR  
MVFR CIGS A BIT OVERNIGHT, BUT STILL EXPECT AT LEAST SOME  
RESTRICTIONS LATE TONIGHT INTO SATURDAY MORNING. CAN'T COMPLETELY  
RULE OUT SOME LIGHT FOG TONIGHT AS WELL, BUT THINK ANY VSBY  
IMPACTS SHOULD BE FAIRLY SHORT-LIVED GIVEN THE WIDESPREAD NATURE  
OF THE CLOUD COVER. CONDITIONS WILL RETURN TO VFR ON SATURDAY,  
WITH GENERALLY LIGHT AND VARIABLE WINDS EXPECTED.  
 
DEITSCH  
 

 
   
PRELIMINARY POINT TEMPS/POPS
 
 
SAINT LOUIS 82 70 89 73 / 20 20 10 40  
QUINCY 78 64 87 69 / 20 20 5 40  
COLUMBIA 82 66 88 70 / 20 20 20 60  
JEFFERSON CITY 83 66 89 71 / 20 20 20 50  
SALEM 80 67 87 70 / 20 20 20 50  
FARMINGTON 82 66 86 70 / 20 30 30 40  
 

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

 
 

 
 
WFO LSX  
 
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