917  
FXUS63 KLSX 261151  
AFDLSX  
 
AREA FORECAST DISCUSSION...UPDATED AVIATION  
NATIONAL WEATHER SERVICE SAINT LOUIS MO  
551 AM CST TUE JAN 26 2021  
   
SHORT TERM
 
(THROUGH LATE WEDNESDAY AFTERNOON)  
ISSUED AT 410 AM CST TUE JAN 26 2021  
 
HAVE CONTINUED THE WINTER WEATHER ADVISORY THROUGH 6 AM. RECENT  
REPORTS OVER THE ADVISORY AREA INDICATE THAT PRECIPITATION THAT HAS  
BEEN OCCURRING OVER THE PAST FEW HOURS HAS BEEN A MIX OF LIGHT  
FREEZING DRIZZLE AND LIGHT SNOW WITH THE ONLY GLAZING ON ELEVATED  
SURFACES. LATEST ASOS/AWOS OBS ARE NOW SHOWING MAINLY SNOW, SO  
EXPECT THAT ICE THREAT IS LESSENING WITH TIME, SO DO NOT NEED TO  
EXTEND THE ADVISORY PAST 6 AM.  
 
LATEST WATER VAPOR IMAGERY IS SHOWING TWO UPPER WAVES, ONE CURRENTLY  
OVER WESTERN IOWA THAT WILL MOVE QUICKLY NORTH OF THE AREA THIS  
MORNING AND ANOTHER OVER SOUTHWEST CONUS. THE FIRST WILL BRING  
ENOUGH ASCENT THROUGH THIS MORNING TO BRING A CHANCE OF LIGHT SNOW  
OR LIGHT FREEZING RAIN THIS MORNING, BUT ANY AMOUNTS WILL BE LIGHT.  
BY THIS AFTERNOON. THIS SYSTEM WILL LIFT NORTHEAST OF THE AREA  
AND EXPECT DRY CONDITIONS UNTIL THE LATE EVENING AND OVERNIGHT  
BEFORE ASCENT BEGINS TO INCREASE AHEAD THE NEXT TROUGH. WHILE THIS  
SYSTEM WILL BE MOVING THROUGH THE AREA FAIRLY QUICKLY, THE  
HREF/NAM/GFS ALL SHOW DECENT ASCENT, SO WENT WITH LIKELY/  
CATEGORICAL POPS FOR SNOW LATE TONIGHT INTO WEDNESDAY MORNING WITH  
ACCUMULATIONS OF 1/2-1". SNOW SHOULD MOVE OUT OF THE AREA BY LATE  
WEDNESDAY AFTERNOON.  
 
WE WILL STAY IN A COLD AIR ADVECTION PATTERN OVER THE NEXT 36 HOURS  
UNDER CLOUD COVER. I DON'T NOT EXPECT MORE THAN A 5 DEGREE  
RECOVERY TODAY, THOUGH LOWS WILL NOT DROP TOO MUCH TONIGHT WITH  
THE CLOUDS. HIGHS TOMORROW WILL BE COLDER WITH THE CAA.  
 
BRITT  
   
LONG TERM
 
(WEDNESDAY NIGHT THROUGH MONDAY)  
ISSUED AT 410 AM CST TUE JAN 26 2021  
 
LATEST GUIDANCE FROM THE GFS AND ECMWF ENSEMBLES IS STILL SHOWING A  
UPPER RIDGE BUILDING ACROSS THE MIDDLE OVER THE CONUS BY LATE IN THE  
WEEK THAT WILL SET UP NORTHWEST FLOW OVER MISSOURI AND ILLINOIS.  
THIS WILL BRING DRY WEATHER TO THE AREA FROM WEDNESDAY NIGHT INTO  
FRIDAY NIGHT AS A LARGE SURFACE HIGH MOVES ACROSS THE REGION. THE  
UPPER RIDGE WILL MOVE EAST ACROSS MIDWEST BY EARLY SATURDAY AT THE  
SAME TIME THAT A TROUGH OVER THE WEST COAST WILL MOVE EAST INTO THE  
PLAINS. BOTH ENSEMBLES AND DETERMINISTIC MODELS ARE SHOWING AN  
ATTENDANT SURFACE LOW MOVING ACROSS MISSOURI AND ILLINOIS  
SATURDAY INTO SUNDAY WITH STRONG MOISTURE TRANSPORT AHEAD OF IT.  
THIS JUSTIFIES CATEGORICAL POPS SATURDAY INTO SATURDAY NIGHT GIVEN  
THE IMPLIED ASCENT WITH THE NEGATIVELY TILTED TROUGH SEEN IN THE  
DETERMINISTIC MODELS. THERE WILL INITIALLY BE A MIX OF RAIN AND  
SNOW WITH THE ONSET OF PRECIPITATION ON SATURDAY MORNING, BUT  
THEN MAINLY RAIN IS EXPECTED SATURDAY AFTERNOON INTO SATURDAY  
NIGHT. THIS TROUGH WILL THEN LIFT OUT THE AREA BY LATE SUNDAY WITH  
UPPER RIDGING BUILDING IN BEHIND IT, SO KEPT SUNDAY AND MONDAY  
DRY.  
 
TEMPERATURES WILL GRADUALLY WARM BACK ABOVE NORMAL AS THE SURFACE  
HIGH MOVES THROUGH THE AREA AND THE SURFACE FLOW TURNS OUT OF THE  
SOUTHWEST AND 850MB TEMPERATURES CLIMB FROM AROUND -5C ON THURSDAY  
MORNING TO AROUND 0-5C ON FRIDAY AND SATURDAY. THIS IS REFLECTED  
WELL BY THE ENSEMBLE GUIDANCE PLUMES.  
 
BRITT  
 

 
   
AVIATION
 
(FOR THE 12Z TAFS THROUGH 12Z WEDNESDAY MORNING)  
ISSUED AT 529 AM CST TUE JAN 26 2021  
 
LOW CLOUDS ARE EXPECTED THROUGH THE PERIOD, WITH IFR CEILINGS  
THROUGH THE PERIOD AT BOTH KUIN AND KCOU WITH IFR/MVFR  
VISIBILITIES MOST OF THE DAY IN FOG. KUIN WILL ALSO HAVE A CHANCE  
OF SNOW AND FREEZING DRIZZLE THIS MORNING WITH MINOR  
ACCUMULATIONS. THE ST. LOUIS METRO TERMINALS WILL ALSO HAVE IFR OR  
LOW MVFR CEILINGS THROUGH THE PERIOD. ALL OF THE TERMINALS WILL  
HAVE A CHANCE OF SNOW AFTER 06Z TONIGHT.  
 
SPECIFICS FOR KSTL:  
 
LIFR CONDITIONS ARE EXPECTED IN LOW CEILINGS AND FOG THROUGH MID  
MORNING, WITH IFR CEILINGS EXPECTED THROUGH THIS EVENING. SNOW  
WILL MOVE INTO THE TERMINAL LATE TONIGHT AND CONTINUE THROUGH  
WEDNESDAY MORNING WITH MINOR ACCUMULATIONS.  
 
BRITT  
 

 
   
LSX WATCHES/WARNINGS/ADVISORIES
 
 
MO...WINTER WEATHER ADVISORY UNTIL 6 AM CST EARLY THIS MORNING FOR  
KNOX MO-LEWIS MO-MARION MO-SHELBY MO.  
 
IL...WINTER WEATHER ADVISORY UNTIL 6 AM CST EARLY THIS MORNING FOR  
ADAMS IL-BROWN IL.  
 

 
 

 
 
WFO LSX  
 
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