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000
FXUS63 KLSX 172010
AFDLSX

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE ST LOUIS MO
310 PM CDT FRI MAY 17 2013

.SHORT TERM...(THROUGH LATE TONIGHT)
ISSUED AT 306 PM CDT FRI MAY 17 2013

SHOWERS HAVE CONTINUED TO PERCOLATE NORTHWARD ACROSS THE CWA THIS
AFTERNOON AS A SLOW MOVING UPPER LOW CONTINUES TO DRIFT TOWARD THE
OHIO VALLEY. WHILE NO REPORTS HAVE BEEN RECEIVED...CANNOT RULE OUT A
RUMBLE OF THUNDER WITH SOME OF THE STRONGER STORMS THIS AFTERNOON
AND THIS EVENING...THOUGH OVERALL EXPECT THE ACTIVITY TO WANE WITH
THE LOSS OF DIURNAL HEATING AND DIMINISH FROM WEST TO EAST AS THE
LOW CONTINUES TO MOVE EAST.

DEWPOINTS TODAY HAVE RISEN TO THE LOW TO MIDDLE 60S AND SHOULD HOLD
IN THE LOW 60S OVERNIGHT. THE COMBINATION OF CALM TO LIGHT WINDS AND
PLENTY OF BOUNDARY LAYER MOISTURE YIELDS CONCERN FOR FOG DEVELOPMENT
TONIGHT. THIS MORNING...OBSERVATIONS IN KANSAS...OKLAHOMA...AND EXTREME
SOUTHWEST MISSOURI INDICATED WIDESPREAD FOG...AND GIVEN THIS AIRMASS
WILL BE MOVING EASTWARD TONIGHT...CANNOT IGNORE THE POTENTIAL FOR
FOG TO DEVELOP DURING THE EARLY OVERNIGHT HOURS. FORECAST SOUNDINGS
INDICATE GREATER POTENTIAL FOR FOG GENERALLY ALONG AND SOUTH OF THE
I-70 CORRIDOR...THOUGH CANNOT RULE OUT SOME LIGHT FOG OR HAZE NEAR
DAYBREAK FOR THE NORTHERN TIER OF THE CWA.

OTHERWISE...AFTER PRECIPITATION TAPERS OFF THIS EVENING ACROSS THE
AREA...A TRANQUIL NIGHT IS EXPECTED WITH OVERNIGHT LOW TEMPERATURES
IN THE LOW TO MIDDLE 60S...SLIGHTLY ABOVE NORMAL FOR THIS TIME OF
YEAR.

PHILLIPSON

.LONG TERM...(SATURDAY THROUGH NEXT FRIDAY)
ISSUED AT 306 PM CDT FRI MAY 17 2013

REMNANTS OF UPPER LEVEL LOW OVER THE OHIO VALLEY COULD STILL
BRING SOME ISOLATED SHOWERS AND A FEW THUNDERSTORMS TO FAR EASTERN
PORTIONS OF FORECAST AREA ON SATURDAY. OTHERWISE...SHOULD SEE MORE
SUNSHINE AND WITH WINDS FROM THE SOUTHEAST TO SOUTH...TEMPERATURES
TO WARM UP INTO THE LOW TO MID 80S.

MILD WEATHER TO PERSIST SATURDAY NIGHT WITH LOWS ONLY IN THE MID TO
UPPER 60S. THERE IS A CHANCE FOR SOME SCATTERED SHOWERS AND A FEW
THUNDERSTORMS LATE...AS A WEAK WARM FRONT LIFTS NORTHWARD THROUGH
FORECAST AREA.

BY SUNDAY...NEXT WEATHER SYSTEM TO APPROACH REGION WITH WINDS
PICKING UP FROM THE SOUTH...GUSTS TO NEAR 25 MPH AT TIMES. LOW LEVEL
MOISTURE WILL BE ON THE INCREASE WITH SOME DECENT CAPES IN THE WARM
SECTOR...SO SHOWERS AND THUNDERSTORMS POSSIBLE...MAINLY OVER
CENTRAL/NORTHEAST MO...WEST CENTRAL IL. HIGHS WILL BE IN THE MID 80S
TO NEAR 90.

AS HAS BEEN THE CASE THE PAST COUPLE OF MODEL RUNS...THE FORWARD
SPEED OF THIS SYSTEM HAS SLOWED DOWN...AS UPPER LEVEL LOW SITS AND
SPINS OVER THE UPPER MIDWEST. SO PCPN WILL SLOWLY INCREASE FROM WEST
TO EAST SUNDAY NIGHT AND MONDAY...BEST CHANCES WITH THIS SYSTEM WILL
BE MONDAY NIGHT AND TUESDAY. CURRENT TIMING HAS FRONT NOT MOVING
THROUGH TIL LATE TUESDAY...EARLY WEDNESDAY...SO PCPN TO LINGER
ACROSS MOST OF FORECAST AREA TIL WEDNESDAY. AS FOR SEVERE CHANCES
WITH THIS SYSTEM...STILL HAVE DECENT CAPES...STRONG DEEP LAYER SHEAR
AND MOISTURE BEGINNING SUNDAY AFTERNOON THROUGH MONDAY EVENING...SO
PORTIONS OF THE FORECAST AREA ARE OUTLOOKED FOR A CHANCE OF SEVERE
WEATHER THROUGH THIS PERIOD.

AS FOR TEMPS...WILL SEE HIGHS IN THE 80S ON MONDAY...EVENTUALLY
COOLING DOWN INTO THE 70S EVERYWHERE THURSDAY AND FRIDAY. LOWS TO
DROP INTO THE 50S BY WEDNESDAY NIGHT AND THURSDAY NIGHT.

BYRD
&&

.AVIATION...(FOR THE 18Z TAFS THROUGH 18Z SATURDAY AFTERNOON)
ISSUED AT 1233 PM CDT FRI MAY 17 2013

A LOW PRESSURE SYSTEM CONTINUES TO SLOWLY SPIN EASTWARD ACROSS
SOUTHERN MO AND INTO THE OHIO VALLEY...WITH ASSOCIATED
PRECIPITATION CONTINUING TO PERCOLATE NORTHWARD OVER EASTERN MO
AND SOUTHERN AND SOUTHWEST IL. HAVE GONE WITH MENTION OF VCSH FOR
METRO TAF SITES THROUGH THIS EVENING...AS IT APPEARS THAT THE MAIN
FOCUS FOR TSRA SHOULD REMAIN WELL SOUTHEAST OF THE TERMINALS. LOSS
OF HEATING AFTER SUNSET SHOULD ACT TO STYMIE ANY ADDITIONAL
DEVELOPMENT IN OUR AREA. CONDITIONS ARE EXPECTED TO REMAIN LOW-END
VFR...THOUGH MVFR CONDITIONS COULD ACCOMPANY SOME OF THE SHOWERS.

FOR TONIGHT THROUGH SATURDAY MORNING...HAVE MAINTAINED TAF TRENDS
FROM THE PREVIOUS ISSUANCE FOR THE DEVELOPMENT OF FOG ACROSS MUCH
OF THE REGION. GIVEN AMPLE MOISTURE AND LIGHT/VAR WINDS EXPECTED
OVERNIGHT...EXPECT MVFR DECREASING TO IFR FOG TO IMPACT KSTL AND
KSUS...WITH VLIFR POSSIBLE FOR KCOU. THERE MAY ALSO BE SOME FOG
DEVELOPMENT FOR A FEW HOURS PRIOR TO DAYBREAK AT KUIN...THOUGH DO
NOT EXPECT CONDITIONS TO DROP BELOW MVFR AT THIS TIME. GRADUAL
IMPROVEMENT WILL OCCUR SATURDAY MORNING...WITH CIGS BECOMING SCT
VFR AS A RIDGE BUILDS INTO EASTERN MO.

SPECIFICS FOR KSTL...

SHOWERS CONTINUE TO PERCOLATE ACROSS EASTERN MO THIS AFTERNOON DUE
TO A SLOW MOVING LOW PRESSURE SYSTEM...THROUGH ARE EXPECTED TO
TAPER OFF AFTER SUNSET WITH A LOSS OF DAYTIME HEATING. WHILE A
RUMBLE OF THUNDER CANNOT BE RULED OUT...FEEL THAT THE FOCUS FOR
THUNDERSTORM ACTIVITY REMAINS WELL SOUTHEAST OF THE TERMINAL...AND
THUS HAVE CONTINUED MENTION OF VCSH. LOW-END VFR CONDITIONS WILL
PREVAIL TODAY...POSSIBLY MVFR AS SHOWERS MOVE THROUGH THE
AREA...THOUGH WILL GENERALLY BE ON THE CUSP BETWEEN MVFR AND VFR
UNTIL LATE TONIGHT. AMPLE MOISTURE AND LIGHT/VAR WINDS OVERNIGHT
WILL RESULT IN MVFR FOG DEVELOPMENT AOA 04Z...DECREASING TO IFR
AFTER 07Z...WITH LITTLE IMPROVEMENT EXPECTED UNTIL AFTER SUNRISE
SATURDAY MORNING. OTHERWISE...SATURDAY IS EXPECTED TO BE
DRY...WITH CIGS BECOMING SCT VFR BY LATE MORNING/EARLY AFTERNOON.

JP
&&

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

$$
WFO LSX