588  
FXUS63 KLSX 232059  
AFDLSX  
 
AREA FORECAST DISCUSSION  
NATIONAL WEATHER SERVICE SAINT LOUIS MO  
359 PM CDT SAT MAR 23 2019  
   
SHORT TERM
 
(THROUGH LATE SUNDAY AFTERNOON)  
ISSUED AT 256 PM CDT SAT MAR 23 2019  
 
THE MAIN CONCERN THROUGH THE PERIOD WILL BE THE POTENTIAL FOR  
THUNDERSTORMS SUNDAY AFTERNOON INTO SUNDAY EVENING. THERE IS THE  
POSSIBILITY FOR ISOLATED TO SCATTERED SEVERE STORMS WITH THE  
GREATEST THREAT FROM MID-AFTERNOON INTO THE EARLY EVENING.  
 
THERE IS LITTLE IMMEDIATE CONCERN WITH THE MAIN FOCUS ON SHOWER  
ACTIVITY OVER SOUTHERN AND CENTRAL PORTIONS OF MISSOURI. THIS  
ACTIVITY RUNS WELL AHEAD OF THE NEXT SYSTEM WITH MID TO HIGH  
CLOUDS STREAMING INTO THE REGION FROM THE WEST/SOUTHWEST.  
 
CURRENT SATELLITE TRENDS, COMBINED WITH MOSAIC RADAR IMAGE,  
MAKE THIS ACTIVITY LOOK MUCH MORE NUMEROUS THAN REALITY. A BROAD  
SURFACE RIDGE THAT STRETCHES FROM THE GREAT LAKES INTO THE  
TENNESSEE VALLEY CONTINUES TO FUNNEL DRY AIR INTO THE AREA FROM  
THE SOUTHEAST. THIS HAS IMPEDED MUCH IN THE WAY OF ANY  
PRECIPITATION THIS AFTERNOON. ALTHOUGH SHOWERS HAVE BEEN HELD IN  
CHECK SO FAR, LOW LEVEL MOISTURE SHOULD BEGIN TO INCREASE  
OVERNIGHT WITH SHOWERS BECOMING MORE NUMEROUS AFTER 00Z IN  
COLUMBIA AND SLOWLY SPREADING EAST FROM THERE. I WOULD EXPECTED  
MUCH OF THE AREA TO BE IMPACTED BY LIGHT SHOWER ACTIVITY AFTER  
MIDNIGHT TONIGHT INTO EARLY SUNDAY MORNING. THIS WILL ONLY BE THE  
FIRST ROUND WITH A LULL IN OVERALL ACTIVITY THROUGH MID-MORNING  
SUNDAY.  
 
THE CLOSED UPPER LEVEL WAVE BEGINS TO TURN MORE EASTERLY LATE  
TONIGHT, PROGGED TO OPEN UP AND TRANSITION INTO A BROAD SHORTWAVE  
DURING THE DAY SUNDAY. AS THIS OCCURS, THE SURFACE LOW AND ITS  
ASSOCIATED MID-LEVEL FEATURE MOVES NEAR THE MISSOURI/IOWA BORDER  
WITH THE COLD FRONT STILL TRAILING BACK OVER CENTRAL MISSOURI  
SUNDAY AFTERNOON. IT IS ALONG THIS FRONT THAT CAMS SHOW ADDITIONAL  
CONVECTION DEVELOPING AFTER 18Z SUNDAY. INITIALLY, SCATTERED  
DISCRETE CELL MAY DEVELOP OVER CENTRAL PORTIONS OF THE STATE, BUT  
GIVEN UNIDIRECTIONAL FLOW, THESE WOULD QUICKLY TAKE ON A LINEAR  
NATURE.  
 
HOWEVER, CONFIDENCE IN MUCH MORE THAN ISOLATED TO SCATTERED  
STRONG TO SEVERE STORMS IS LOW. THE MAIN QUESTION WILL BE IN HOW  
QUICKLY REMNANT RAINFALL MOVES EAST THROUGH SUNDAY MORNING. THEN  
THE MAIN INHIBITORS LOOK TO BE CLOUD COVER TAMPING DOWN SURFACE  
HEATING SUNDAY AFTERNOON. WHILE 0-6KM SHEAR IS AROUND 40KTS,  
THERE IS A VERY NARROW WINDOW (20Z-00Z) FOR INCREASED MLCAPE OF  
1000-1500 J/KG, LARGELY SUPPORTED OVER SOUTH-CENTRAL AND SOUTHEAST  
MISSOURI. FURTHER NORTH AND EAST, VALUES DECREASE TO AROUND 600  
J/KG NEAR STL AND ZERO NORTH OF I-70.  
 
ALL-IN-ALL, SHOULD CONVECTION MATERIALIZE SUNDAY AFTERNOON,  
INITIAL THREATS WILL BE HAIL/DAMAGING WIND OVER CENTRAL AND  
SOUTHEAST MISSOURI, BEFORE SHIFTING TO MAINLY A WIND THREAT AS THE  
LINE CONGEALS. THERE IS THE SLIGHTEST POTENTIAL THAT A STORM OR  
TWO COULD HAVE AN ISOLATED, QUICK AND WEAK TORNADO, BUT LOW LEVEL  
SHEAR IS SOMEWHAT MARGINAL, LEADING TO LESS CONFIDENCE IN THIS  
OCCURRING. OTHERWISE, EXPECT THE LINE TO QUICKLY MOVE EAST OF THE  
CWA AROUND OR JUST AFTER 00Z. GIVEN THE EAST/SOUTHEAST TRAJECTORY  
OF THE SURFACE LOW THROUGH CENTRAL ILLINOIS, COULD SEE SOME  
LINGERING SHOWER ACTIVITY BEHIND THE FRONT, BUT SEVERE WEATHER  
POTENTIAL SHOULD WANE AS THE EVENING PROGRESSES.  
 
MAPLES  
   
LONG TERM
 
(SUNDAY NIGHT THROUGH NEXT SATURDAY)  
ISSUED AT 256 PM CDT SAT MAR 23 2019  
 
A MAJORITY OF THE LONG TERM LOOKS TO BE RATHER QUIET. ANY  
POTENTIAL FOR PRECIPITATION LIES AT THE VERY BEGINNING AND LATER  
IN THE PERIOD.  
 
SUNDAY'S SURFACE LOW CONTINUES TO MOVE EAST OF THE AREA WITH A  
COLD FRONT RESULTING IN COLD AIR ADVECTION THROUGH SUNDAY NIGHT.  
WHILE MOST OF THE PRECIPITATION MOVES OUT, THERE MAY BE ENOUGH  
LINGERING SURFACE MOISTURE AND WEAK MID-LEVEL LIFT TO RESULT IN  
WIDELY SCATTERED/ISOLATED SHOWERS, PRIMARILY OVER INTERIOR SECTION  
OF ILLINOIS. OTHERWISE, THE TREND WILL BE TOWARD DRIER AND COOLER  
CONDITIONS LATE SUNDAY NIGHT INTO MONDAY.  
 
UPPER LEVEL FLOW TILTS MORE NORTHWESTERLY AS A RIDGE BUILDS INTO  
THE CENTRAL U.S. TUESDAY. ANOTHER UPPER LEVEL SHORTWAVE SEEMS TO  
PASS SOUTHWEST OF THE AREA, BUT SURFACE RIDGING WILL BEGIN  
BUILDING INTO THE UPPER MIDWEST AND GREAT LAKES REGION. THIS RIDGE  
BROADENS TO ENCAPSULATE MUCH OF THE EASTERN U.S. THROUGH THE  
MIDWEEK PERIOD. THIS SHOULD BE EFFECTIVE IN KEEPING US DRY  
THROUGH MUCH OF THE WORK WEEK. UPPER RIDGING OVER THE CENTRAL  
U.S. CONTINUES TO AMPLIFY THROUGH THROUGH MIDDLE OF THE WEEK,  
EVENTUAL BUILDING EASTWARD BY LATE WEEK. SO, NOT ONLY DRY WEATHER  
IS FAVORED, BUT MILDER TEMPERATURES, AS WELL.  
 
THE MAIN QUESTION WILL BE AS TO HOW LONG RIDGING REMAINS  
INFLUENTIAL ENOUGH TO KEEP PRECIPITATION OUT OF THE AREA. THIS  
RIDGE BEGINS TO TAKE ON AN ELONGATED FORM FROM THE NEW ENGLAND  
STATES, SOUTHWEST TO THE NORTHERN GULF OF MEXICO. IT IS ON THE  
WESTERN PERIPHERY OF THIS RIDGE WHERE A SURFACE LOW IS PROJECTED  
TO DEVELOP AND TAKE A NORTHEAST PATH OVER THE CENTRAL CONUS. WHERE  
THIS SETS UP COULD BE KEY AS TO HOW QUICKLY PRECIPITATION IN  
INTRODUCED BACK INTO THE FORECAST LATER THIS WEEK. FOR NOW, LOOKS  
LIKE SLIGHT TO CHANCE POPS WILL BE THE BEST CALL WITH TEMPS  
RETURNING TO THE 60S FROM WEDNESDAY INTO FRIDAY.  
 
MAPLES  
 

 
   
AVIATION
 
(FOR THE 18Z TAFS THROUGH 18Z SUNDAY AFTERNOON)  
ISSUED AT 1221 PM CDT SAT MAR 23 2019  
 
IN A NUTSHELL, VFR CONDITIONS ARE EXPECTED THROUGH MUCH OF THE  
PERIOD WITH BREEZY SOUTHERLY SURFACE FLOW. THUNDERSTORM POTENTIAL  
SHOULD HOLD OFF IN MOST AREAS UNTIL AFTER 18Z SUNDAY.  
 
LOW PRESSURE OVER THE PLAINS WILL CONTINUE TO RESULT IN INCREASING  
MID AND UPPER LEVEL MOISTURE OUT OF THE WEST/SOUTHWEST THROUGH THE  
AFTERNOON. MID AND HIGH CLOUDS WILL STREAM IN AHEAD OF THE SYSTEM,  
BUT GIVEN DRY SURFACE LAYER, PRECIPITATION SHOULD BE HELD AT BAY  
THROUGH AT LEAST LATE AFTERNOON/EARLY EVENING.  
 
LOW LEVEL MOISTURE WILL GRADUALLY INCREASE WITH BETTER RH  
PROFILES IN THE SOUNDINGS TO SUPPORT SHOWERS THIS EVENING. WE CAN  
EXPECT SCATTERED SHOWERS TO SPREAD WEST TO EAST FROM CENTRAL  
MISSOURI AROUND 00Z INTO ILLINOIS AFTER 03Z. A FEW WIDELY  
SCATTERED OR ISOLATED SHOWER CANNOT BE RULED OUT OF AHEAD OF THIS,  
BUT WILL BE HIT OR MISS, SHORT-LIVED AND LIGHT IN NATURE (VCSH IN  
THE TAF).  
 
OTHERWISE, CLOUD BASES REMAIN MID-LEVEL OR HIGHER FOR THE MOST  
PART. KUIN MAY DIP INTO MVFR SUNDAY MORNING AS LOW PRESSURE TRACKS  
INTO NORTHERN MISSOURI. VISIBILITY WILL LARGELY BE UNRESTRICTED  
WITH EXCEPTION TO THUNDERSTORMS. CHANCES FOR THUNDER SHOULD HOLD  
OFF UNTIL THE TAIL END OR AFTER THE TAF PERIOD.  
 
SPECIFICS FOR KSTL:  
 
VFR CONDITIONS ARE EXPECT TO STRETCH FROM THIS AFTERNOON INTO  
SUNDAY WITH BREEZY SOUTHEASTERLY WINDS TURNING OUT OF THE SOUTH  
AND EVENTUALLY SOUTHWEST THROUGH THE DAY SUNDAY. WHILE RAIN  
POTENTIAL INCREASE THIS EVENING, THE MAIN CONCERN WILL BE THE  
THREAT FOR THUNDERSTORMS SUNDAY AFTERNOON.  
 
LOW PRESSURE WILL TRACK FROM THE PLAINS TODAY INTO NORTHERN  
MISSOURI AND CENTRAL ILLINOIS SUNDAY AND SUNDAY EVENING. CURRENT  
SATELLITE AND RADAR TRENDS SHOW MID AND HIGH CLOUD STREAMING IN  
WITH MUCH OF WHAT'S ON RADAR NO REACHING THE GROUND OVER CENTRAL  
MISSOURI. A DRY SURFACE LAYER WILL CONTINUE TO IMPEDE THE ONSET  
WITH BETTER POTENTIAL FOR SCATTERED SHOWERS LATE TONIGHT INTO  
EARLY SUNDAY AS LOW LEVEL MOISTURE GRADUALLY CLIMBS.  
 
SHOWERS AREN'T LIKELY TO BE CONTINUOUS SUNDAY, BUT MORE SO OFF/ON.  
THERE IS LIKELY TO BE A LULL FROM MID TO LATE SUNDAY MORNING INTO  
EARLY SUNDAY AFTERNOON. A COLD FRONT STRETCHING TO THE SOUTH OF  
THE SYSTEM WILL THEN PUSH FROM WEST TO EAST THROUGH THE AREA.  
EXPECT ADDITIONAL SHOWER DEVELOPMENT IN TO MID AFTERNOON WITH BEST  
POTENTIAL FOR THUNDERSTORMS BETWEEN 21 AND 00Z. ANY SUB-VFR  
VISIBILITIES/CEILINGS WILL LIKELY BE RESTRICTED TO HEAVIER RAIN  
RELATED TO THUNDERSTORM ACTIVITY SUNDAY AFTERNOON/EVENING.  
 
MAPLES  
 

 
   
HYDROLOGY
 
 
 
MAJOR RIVER FLOODING IS ONGOING AT SAVERTON LOCK AND DAM ON THE  
MISSISSIPPI RIVER, OTHERWISE, SEVERAL LOCATIONS ON THE MISSISSIPPI  
RIVER WILL CONTINUE TO BE IN OR ARE FORECAST TO REACH MODERATE  
FLOODING. IN ADDITION, THE MISSOURI RIVER AT JEFFERSON CITY IS  
FORECAST TO REACH MODERATE FLOODING. THE LOCAL SPRING FLOOD  
OUTLOOK WILL BE UPDATED NEXT WEEK, NO LATER THAN THURSDAY, MARCH  
28.  
 

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

 
 

 
 
WFO LSX  
 
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