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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