000
FXUS63 KLSX 120840
AFDLSX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ST LOUIS MO
340 AM CDT WED JUN 12 2013

.SHORT TERM...(THROUGH LATE THIS AFTERNOON)
ISSUED AT 337 AM CDT WED JUN 12 2013

MAIN CONCERN DEALS WITH POTENTIAL FOR SEVERE WEATHER THIS AFTERNOON
INTO THE EVENING HOURS OVER PARTS OF THE CWA IF THUNDERSTORMS ARE
ABLE TO DEVELOP.  IF THUNDERSTORMS DO DEVELOP...THEN THEY WILL
LIKELY BE SEVERE...PARTICULARLY OVER NORTHEAST MISSOURI INTO CENTRAL
ILLINOIS WITH DAMAGING WIND GUSTS IN EXCESS OF 70 MPH...LARGE HAIL
AND ISOLATED TORNADOES.

EXPECT MAINLY DRY CONDITIONS THROUGH THE MORNING HOURS AS THE
THUNDERSTORM COMPLEX CURRENTLY OVER WESTERN IOWA STAYS NORTH OF THE
AREA PER THE RAP FORWARD PROPAGATION VECTORS.  OBSERVED AND FORECAST
SOUNDINGS STILL SHOW A VERY PRONOUNCED WARM LAYER BETWEEN 900-650MB
THROUGH LATE AFTERNOON WHICH SHOULD LIMIT THUNDERSTORM DEVELOPMENT.
THEREAFTER...THE TAIL END OF THE TROUGH CURRENTLY OVER THE HIGH
PLAINS WILL REACH THE MISSISSIPPI RIVER WHICH WILL ACT TO WEAKEN
THIS WARM LAYER AS THE ATTENDANT COLD FRONT MOVES SOUTHEAST ACROSS
THE CWA.  MOST MODEL SOUNDINGS STILL SHOW SOME CONVECTIVE INHIBITION
OR VERY NARROW POSITIVE CAPE UP TO 700MB WHICH MAY KEEP
THUNDERSTORMS NORTH AND EAST OF THE AREA.  WITH THIS SAID...MID
LEVEL FORCING AND LOW LEVEL MOISTURE CONVERGENCE IS WORTH KEEPING
SCATTERED THUNDERSTORMS IN THE FORECAST LATE THIS AFTERNOON INTO THE
EVENING AS THE COLD FRONT MOVES ACROSS THE CWA.  INSTABILITY AND
SHEAR PARAMETERS FAVOR SEVERE THUNDERSTORMS WITH LATE AFTERNOON
MLCAPES AROUND 3000 J/KG AND 0-6KM SHEAR OF 40-50KTS.  RELATIVELY
DRY AIR BELOW 700MB FAVORS THE POTENTIAL FOR DAMAGING WINDS
GUSTS...AND THERE IS A LARGE AMOUNT OF CAPE BETWEEN -10 AND -30C
WHICH SUGGESTS THE POTENTIAL FOR LARGE HAIL.  SHEAR IS LINEAR IN THE
LOWEST LEVELS...THOUGH 0-1KM SHEAR NEAR 25KTS SUGGESTS TORNADOES ARE
ALSO POSSIBLE.

DID NOT CHANGE FORECAST HIGHS TODAY AS CURRENT TEMPERATURES ARE IN
THE 70S AND THERE WILL BE DECENT MIXING UP TO 850MB TODAY WITH MORE
SUN THAN YESTERDAY.

BRITT

.LONG TERM...(TONIGHT THROUGH TUESDAY)
ISSUED AT 337 AM CDT WED JUN 12 2013

AFTERNOON/EVENING CONVECTION SHOULD BE EXITING THE AREA BY 06Z.
CANNOT RULE OUT A STRAY SHOWER OR STORM OUT AHEAD OF OR RIGHT ON THE
COLD FRONT AS IT PUSHES THROUGH EAST CENTRAL AND SOUTHEAST MISSOURI
AND SOUTHERN ILLINOIS.  NORTHWEST FLOW WILL BRING COOLER AND DRIER
AIR WITH SURFACE DEWPOINTS DROPPING BACK INTO THE UPPER 50S AND
LOWER 60S.  850MB TEMPS ALSO DROP INTO THE LOW TO MID TEENS BEHIND
THE FRONT.  MODELS HAVE BEEN CONSISTENTLY AMPLIFYING THE FLOW
THURSDAY INTO FRIDAY WITH A FULL LONGWAVE TROF OVER THE EAST COAST
AND THE UPPER LEVEL RIDGE BUILDING ACROSS THE GREAT PLAINS INTO THE
UPPER MIDWEST.  THIS SHOULD KEEP THE LOW LEVEL RIDGE LOCKED IN
ACROSS THE MISSISSIPPI VALLEY AT LEAST THROUGH FRIDAY.  SEASONABLY
COOL GUIDANCE TEMPS LOOK PRETTY REASONABLE WITH AFOREMENTIONED COOL
AND DRY RIDGE IN PLACE.  THERE IS A SMALL CHANCE THAT INCREASING
WARM ADVECTION ON THE WESTERN PERIPHERY OF THE LOW LEVEL RIDGE MAY
PRODUCE ISOLATED SHOWERS OR STORMS FRIDAY OVER PARTS OF CENTRAL AND
NORTHEAST MISSOURI SO HAVE SOME SLIGHT CHANCE POPS IN THOSE AREAS.

THE WEEKEND IS LOOKING MORE AND MORE STORMY AS THE UPPER LEVEL RIDGE
BREAKS DOWN IN RESPONSE TO A SHORTWAVE WHICH IS PULLED NORTHEAST OUT
OF THE GULF OF MEXICO.  THIS WAVE IS LIKELY TO HAVE QUITE A BIT OF
MOISTURE ASSOCIATED WITH IT.  AM UNSURE WHAT THE POTENTIAL FOR
SEVERE WEATHER WILL BE AT THIS TIME...BUT IT DOES LOOK LIKE THERE
WILL BE THUNDERSTORMS ON AND OFF FROM SATURDAY AFTERNOON AT LEAST
THROUGH SUNDAY NIGHT OR MONDAY AND SOME LOCALLY HEAVY RAIN MAY BE
POSSIBLE.  TUESDAY LOOKS DRIER AS THE WAVE MOVES EAST AND WEAK
RIDGING BUILDS BACK ACROSS THE MID MISSISSIPPI VALLEY.  TEMPERATURES
THROUGH THE PERIOD LOOK TO BE NEAR NORMAL.

CARNEY

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z WEDNESDAY NIGHT)
ISSUED AT 1153 PM CDT TUE JUN 11 2013

VFR CONDITIONS ARE EXPECTED TO DOMINATE MUCH OF THE PERIOD. BOUTS
OF HIGH CLOUDS WILL CONTINUE TO IMPACT EASTERN MO AND WESTERN
ILLINOIS INTO WED MORNING. SOUTH SOUTHWESTERLY SURFACE WINDS WILL
THEN INCREASE AROUND MID-MORNING ON WEDNESDAY WITH GUSTS AOA 25
KTS. THERE IS A CHANCE OF SHOWERS AND THUNDERSTORMS ACROSS
PORTIONS OF NE MO AND WEST CENTRAL IL DURING THE LATER PART OF
WEDNESDAY AFTERNOON AND INTO THE EARLY EVENING AS A COLD FRONT
DROPS SOUTH INTO THE AREA. CONFIDENCE AT THIS TIME IS TOO LOW FOR
AN ACTUAL AIRPORT IMPACT TO INCLUDE IN THE KUIN TAF.

SPECIFICS FOR KSTL...

VFR CONDITIONS ARE EXPECTED TO DOMINATE MUCH OF THE PERIOD WITH
BOUTS OF HIGH CLOUDS CONTINUING OVERNIGHT THROUGH WEDNESDAY
MORNING. SOUTH SOUTHWESTERLY SURFACE WINDS WILL THEN INCREASE
AROUND MID-MORNING ON WEDNESDAY WITH GUSTS AOA 25 KTS. A COLD
FRONT WILL BE DROPPING INTO EASTERN MO ON WEDNESDAY EVENING AND IT
COULD BE ACCOMPANIED BY SCATTERED THUNDERSTORMS. IF THERE IS ANY
IMPACT AT KSTL...CURRENT INDICATIONS ARE THAT 04-07Z WOULD BE THE
OPTIMAL TIME FRAME...HOWEVER CONFIDENCE IS TOO LOW TO MENTION AT
THIS TIME.

GLASS

&&

.PRELIMINARY POINT TEMPS/POPS...
SAINT LOUIS     96  70  86  65 /  30  40   5   5
QUINCY          92  64  81  60 /  50  40   0   5
COLUMBIA        95  68  84  64 /  10  20   0  10
JEFFERSON CITY  96  69  84  65 /  10  10   0  10
SALEM           95  70  82  61 /  30  50   5   0
FARMINGTON      95  68  84  60 /  10  30   5   5

&&

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

$$

WFO LSX