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000
FXUS63 KLSX 170457
AFDLSX

AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE ST LOUIS MO
1157 PM CDT THU MAY 16 2013

.UPDATE...
ISSUED AT 905 PM CDT THU MAY 16 2013

UPDATED FORECAST TO TONE DOWN POPS FOR THE REST OF THE EVENING AND
PULL THUNDER UNTIL AFTER 06Z. SHORT-RANGE GUIDANCE CONTINUES TO
SHOW AN INCREASE IN AREAL COVERAGE AND INTENSITY OF PRECIPITATION
OVERNIGHT AS A WEAK LOW LEVEL JET FOCUSES OVER EASTERN MISSOURI
AND SOUTHWEST ILLINOIS. HAVE KEPT CHANCE SHOWERS WITH ISOLATED
THUNDER GOING AFTER 06Z IN SOUTHEAST MO AND EXTREME SOUTHWEST IL
TO COVER THIS. OTHERWISE...FORECAST LOOKS ON TRACK FOR THE REST OF
THE NIGHT.

CARNEY

&&

.SHORT TERM...(THROUGH LATE TONIGHT)
ISSUED AT 334 PM CDT THU MAY 16 2013

SO FAR THIS AFTERNOON...CONVECTION HAS PRIMARILY BEEN LOCATED OVER
CENTRAL MO IN ADVANCE OF SHORTWAVE ROTATING WWD AROUND THE N SIDE OF
THE UPPER LEVEL LOW...WHICH IS CURRENTLY LOCATED OVER NW AR.
ACTIVE CONVECTION IS ALSO OCCURRING ALONG STALLED FRONTAL BOUNDARY
AND REMNANT OUTFLOW FROM EXTREME SE IA INTO CENTRAL IL...JUST
OUTSIDE OF OUR CWA.

TSRA CHANCES OVER THE NEXT FEW HOURS WILL BE SHIFTING TO S SECTIONS
OF THE CWA...AND TO NEAR THE VICINITY OF THE E-NE DRIFTING UPPER
LEVEL LOW...FOR MOST OF THE EVENING AND INTO THE OVERNIGHT HOURS.
FOR NOW I`VE USED A FAIRLY BROAD BRUSH APPROACH FOR POPS.  ITS
CERTAINLY POSSIBLE THAT THE N EDGE OF THE POP GRADIENT ISN`T TIGHT
ENOUGH...BUT GIVEN THE UNCERTAINLY ON WHERE THE N EDGE WILL SET UP
THIS SHOULD LEAVE SOME WIGGLE ROOM FOR NOWCAST-TYPE TWEEKS DURING
THE EVENING/OVERNIGHT BASED ON RADAR TRENDS.  HIGHEST POPS WILL BE
OVER OUR FAR S COUNTIES...IN THE HIGH CHANCE RANGE...WITH ADDITIONAL
REFINEMENT CERTAINLY POSSIBLE BASED ON RADAR TRENDS.

TEMPS SHOULD BE BOTTOMING OUT IN THE 60S OVER MOST OF THE AREA.

TRUETT

.LONG TERM...(FRIDAY THROUGH NEXT THURSDAY)
ISSUED AT 334 PM CDT THU MAY 16 2013

(FRIDAY THROUGH SUNDAY)

UPPER LEVEL LOW CONTINUES TO WEAKEN AND LIFT OUT OF FORECAST AREA ON
FRIDAY. STILL HAVE DECENT INSTABILITY AND LIFT...SO WILL SEE
SCATTERED SHOWERS AND THUNDERSTORMS OVER SOUTHEAST MO CONTINUE TO
DEVELOP AND SPREAD NORTH ACROSS REST OF THE REGION...WITH BEST
CHANCES OVER EASTERN HALF OF FORECAST AREA. AS FOR HIGH TEMPS...MID
70S TO LOW 80S IS EXPECTED.

SLIGHT CHANCE OF SHOWERS AND THUNDERSTORMS MAINLY FRIDAY EVENING FOR
AREAS ALONG AND EAST OF MISSISSIPPI RIVER. OTHERWISE...DRY AND MILD
CONDITIONS TO PERSIST WITH LOWS IN THE LOW TO MID 60S.

STILL DEALING WITH WEAKENING UPPER LEVEL SYSTEM THAT WILL BE OVER
THE OHIO VALLEY BY SATURDAY. COULD SEE SCATTERED SHOWERS AND
THUNDERSTORMS OVER FAR EASTERN PORTIONS OF FORECAST AREA ON BACKSIDE
OF SYSTEM DURING THE DAY ON SATURDAY. OTHERWISE...DRY CONDITIONS FOR
MOST LOCATIONS THROUGH SATURDAY NIGHT. HIGHS WILL BE IN THE LOW TO
MID 80S...WITH LOWS IN THE MID TO UPPER 60S SATURDAY NIGHT.

ON SUNDAY...NEXT WEATHER SYSTEM APPROACHES AREA...BUT MODELS
CONTINUE TO SLOW THIS SYSTEM DOWN. SO BACKED OFF ON POPS A
BIT...WITH LOW CHANCE POPS OVER CENTRAL/NORTHEAST MO...WEST CENTRAL
IL. HIGHS ON SUNDAY WILL REMAIN MILD IN THE MID TO UPPER 80S.

(SUNDAY NIGHT THROUGH THURSDAY)

SLOWLY INCREASED POPS FROM WEST TO EAST SUNDAY NIGHT AND MONDAY AS
COLD FRONT MOVES CLOSER TO THE AREA. BOTH 12Z GFS AND ECMWF NOW HAVE
FRONT PROGGED TO NOT SLIDE THROUGH FORECAST AREA TIL LATE IN THE DAY
ON TUESDAY. SO INCREASED POPS FOR PORTIONS OF THE FORECAST AREA ON
TUESDAY AND TUESDAY NIGHT. AS FOR CHANCE OF SEVERE WEATHER ON MONDAY
AFTERNOON AND EVENING...STILL POSSIBLE AS THERE IS DECENT MU
CAPES...LOW LEVEL MOISTURE AND SHORTWAVE ENERGY...SO WILL KEEP
MENTION IN HWO.

BEYOND THAT...PCPN TO TAPER OFF ON WEDNESDAY...WITH ANOTHER CHANCE
FOR SHOWERS AND THUNDERSTORMS ON THURSDAY AS NEXT SYSTEM APPROACHES
REGION FROM THE SOUTHWEST.

HIGHS NEAR NORMAL IN THE MID TO UPPER 70S TUESDAY THROUGH
THURSDAY...WITH LOWS EACH NIGHT IN THE MID 50S TO LOW 60S.

BYRD

&&

.AVIATION...(FOR THE 06Z TAFS THROUGH 06Z FRIDAY NIGHT)
ISSUED AT 1158 PM CDT THU MAY 16 2013

LO CIGS ASSOCIATED WITH MORE OF THE CORE OF THE UPPER LEVEL
SYSTEM TO OUR SW WILL EDGE CLOSER TO CNTRL MO AND STL METRO LATE
TONIGHT AND THEN GET SHUNTED OFF TO THE E...AUGMENTED ON FRIDAY BY
DIURNAL INFLUENCES...WITH CLEARING EXPECTED HEADING INTO FRIDAY
EVENING...FOR A TIME. MAY TRIP IFR CIGS AT KCOU AND STL METRO
SITES LATE TONIGHT AND EARLY FRIDAY MORNING BUT STILL THINK IFR
SHOULD STAY TO THE S. A BETTER LO STRATUS AND FOG SETUP APPEARS
TO EXIST ON FRIDAY NIGHT...ESPECIALLY FOR STL METRO SITES...AS
MOISTURE NEVER REALLY GETS SCOURED OUT BEHIND SYSTEM AND WITH SOME
CLEARING EXPECTED AND LIGHT WINDS. ANOTHER ROUND OF SCT TSRA
APPEARS IN THE OFFING FRIDAY AFTERNOON AS UPPER LEVEL SYSTEM WILL
STILL BE CLOSE ENOUGH.

SPECIFICS FOR KSTL...DETERIORATING CONDITIONS EXPECTED LATE
TONIGHT AND EARLY FRIDAY MORNING WITH IFR POSSIBLE BUT FOR NOW
HAVE FAVORED THE LO-END MVFR OF THE PREVIOUS TAF...IMPROVEMENT TO
CIGS ABOVE 2KFT EXPECTED ON FRIDAY WITH PARTIAL CLEARING AND
PERHAPS ANOTHER ROUND OF LO STRATUS AND FOG FRIDAY NIGHT. BEST
PCPN CHCS AFTER EARLY THIS EVENING WILL BE FRIDAY AFTERNOON WITH
TSRA DEVELOPING WITH THE HEATING OF THE DAY.

TES

&&

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

$$

WFO LSX