000
FXUS63 KLSX 171752
AFDLSX

AREA FORECAST DISCUSSION...UPDATED AVIATION
NATIONAL WEATHER SERVICE ST LOUIS MO
1252 PM CDT FRI MAY 17 2013

.SHORT TERM...(TODAY AND TONIGHT)
ISSUED AT 313 AM CDT FRI MAY 17 2013

THE MAIN FEATURE OF INTEREST TODAY IS THE UPPER LOW WHICH PROFILER
AND WATER VAPOR SUGGEST IS CURRENTLY LOCATED ACROSS EXTREME SRN MO
NEAR WEST PLAINS. THE MODELS ARE IN RELATIVELY GOOD AGREEMENT
TRACKING THE LOW E/NEWD TODAY WITH THE MORE SRN POSITION OF THE
LOCAL WRF AND RUC PREFERRED. THIS TRACK WOULD TAKE THE LOW ACROSS
THE EASTERN OZARKS THIS MORNING AND INTO SRN IL THIS AFTENOON. THE
BIGGEST UNCERTAINTY WITH THIS SYSTEM IS THE N/NW EXTENT OF
PRECIPITATION AND COVERAGE. CLOUD TOPS HAVE BEEN COOLING THE LAST
FEW HOURS IS ASSOCIATION WITH AN INCREASING AMOUNT OF SHOWERS. THE
EXPLICIT GUIDANCE GENERALLY DEPICTS SCATTERED COVERAGE
DIMINISHING WITH NORTHWARD EXTENT. THIS SEEMS REASONABLE AND HAS
BEEN GENERALLY ACCEPTED WITH THE HIGHEST POPS ACROSS SE MO INTO
SRN IL. THE THREAT OF CONVECTION SHOULD INCREASE LATER THIS
MORNING IS ASSOCIATION WITH HEATING AND DESTABILIZATION. THE UPPER
LOW SHOULD BE IN SRN IL BY EARLY EVENING...DEPARTING TO THE EAST
NORTHEAST. ANY PRECIPITATION IN THE WAKE OF THE LOW SHOULD BE
STRONGLY TIED TO HEATING...DISSIPATING DURING THE EVENING.

GLASS

.LONG TERM...(SATURDAY THROUGH THURSDAY)
ISSUED AT 313 AM CDT FRI MAY 17 2013

SATURDAY LOOKS LARGELY DRY AS A RIDGE ALOFT BUILDS INTO THE AREA
IN ASSOCIATION WITH OVERALL UPSTREAM AMPLIFICATION. LOW LEVEL WAA
WILL INCREASE AND THIS COMBINED WITH LESS CLOUD COVER WILL RESULT
IN WARMER TEMPERATURES. THE CHANCE OF SHOWERS AND THUNDERSTORMS
WILL RE-ENTER THE PICTURE ON SAT NIGHT IN RESPONSE TO LOW LEVEL
WAA/MCON VIA A SWLY LLJ...BRINGING THE POTENTIAL FOR ELEVATED
ACTIVITY TO THE NORTH OF A SLOWLY LIFTING WARM FRONT. THE HIGHEST
PROBABILIT AT THIS TIME APPEARS TO BE ACROSS NRN MO INT CENTRAL
IL. THERE COULD BE ONGOING/RESIDUAL ELEVATED ACTIVITY NORTH OF THE
WARM FRONT ACROSS NE MO/WEST CENTRAL IL ON SUNDAY MORNING.
OTHERWISE INCREASING SOUTHERLY FLOW AND WAA SHOULD RESULT IN
CONTINUED WARMER TEMPERATURES WITH SOME LOCATIONS PUSHING 90
DEGREES.

A VERY ACTIVE PERIOD WILL BEGIN TO UNFOLD LATE SUNDAY AFTERNOON
AND CONTINUE THROUGH AT LEAST TUESDAY NIGHT AS RATHER DEEP AND
BROAD UPPER TROF/UPPER LOW MOVES SLOWLY EAST AND A SERIES OF SHORT
WAVES EJECT E/NEWD. A MOIST AND VERY UNSTABLE AIR MASS WILL BE IN
PLACE AND THIS COMBINED WITH FAVORABLE DEEP LAYER SHEAR WILL
SUPPORT MULTIPLE SEVERE WEATHER EPISODES OVER A 3 DAY PERIOD
MIGRATING WEST TO EAST ACROSS THE CWA WITH THE MOST ACTIVE PERIOD
FROM MONDAY THROUGH TUESDAY NIGHT.

GLASS

&&

.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.
&&

$$

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