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000
FXUS62 KCAE 181420
AFDCAE

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE COLUMBIA SC
1020 AM EDT TUE JUN 18 2013

.SYNOPSIS...
MOISTURE WILL REMAIN HIGH TODAY AND TONIGHT ASSOCIATED WITH A WEST
TO EAST ORIENTED FRONTAL ZONE. THE FRONT WILL BEGIN TO SHIFT A
LITTLE FARTHER SOUTH WEDNESDAY AND MOISTURE WILL DIMINISH
SOMEWHAT.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
UPDATE...WEAK FRONTAL BOUNDARY REMAINS NORTHWEST OF THE FORECAST
AREA WITH WSR-88D RETURNS SHOWING SCATTERED SHOWERS OVER THE
CENTRAL MIDLANDS THROUGH THE CSRA. WITH SOME CLEARING ALLOWING
TEMPERATURES TO RISE INTO THE LOWER 80S EXPECT SHOWERS TO INCREASE
IN COVERAGE OVER THE NEXT COUPLE OF HOURS. MAIN CONCERN REMAINS
POTENTIAL FOR HEAVY RAIN THIS AFTERNOON AS PWAT VALUES WILL AGAIN
BE AROUND 2 INCHES. HAVE INCREASED POPS TO ACCOUNT FOR CURRENT
RADAR RETURNS AND ADJUSTED TEMPERATURES UP A DEGREE OR TWO.

PREVIOUS DISCUSSION...HIGH MOISTURE WILL CONTINUE TODAY AHEAD OF
THE SLOW MOVING FRONT. CONVERGENCE ASSOCIATED WITH THE
FRONT...HEATING...PLUS ANOTHER IN A SERIES OF MID-LEVEL SHORTWAVE
TROUGHS WILL SUPPORT NUMEROUS SHOWERS AND THUNDERSTORMS.

RADAR TRENDS INDICATE THE BATCH OF THUNDERSTORMS IN WESTERN GEORGIA
EARLY THIS MORNING WILL REACH THE WEST PART OF THE FORECAST AREA
AROUND 14Z. THE SPC WRF DISPLAYS THESE THUNDERSTORMS MOVING
THROUGH MOST OF THE FORECAST AREA DURING THE 16Z TO 20Z TIME
FRAME.

PRECIPITABLE WATER AROUND 2 INCHES AND POSSIBLE TRAINING SUPPORTS
VERY HEAVY RAIN WITH SOME OF THE THUNDERSTORMS. LOCALIZED FLOODING
WILL BE POSSIBLE. CLOUDINESS SHOULD LIMIT INSTABILITY. THE NAM
DISPLAYS SURFACE-BASED LI/S -3 TO -4 TODAY AND THIS WEAK
INSTABILITY APPEARS REASONABLE BECAUSE OF THE CLOUDINESS AND
NUMEROUS SHOWERS. HOWEVER...THE MODELS AND ESPECIALLY THE GFS
SHOW SIGNIFICANT SHEAR. THE NAM DISPLAYS H85 WIND INCREASING TO
25 TO 30 KNOTS...THE ECMWF 30 TO 35 KNOTS...AND THE GFS 35 TO 40
KNOTS. HEAVY PRECIPITATION LOADING AND THE SHEAR SUPPORTS
ORGANIZED THUNDERSTORMS WITH DAMAGING WIND POSSIBLE.

LEANED TOWARD THE COOLER TEMPERATURE GUIDANCE BECAUSE OF
CLOUDINESS TODAY. USED AN AVERAGE OF THE NAM AND GFS FOR THE WIND
FORECAST.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH WEDNESDAY NIGHT/...
CONVERGENCE ASSOCIATED WITH THE SLOW MOVING FRONT SUPPORTS NUMEROUS
SHOWERS AND THUNDERSTORMS TONIGHT. LEANED TOWARD THE HIGHER POP
GUIDANCE. HIGH PRECIPITABLE WATER AND POSSIBLE TRAINING WILL
SUPPORT VERY HEAVY RAIN WITH SOME OF THE THUNDERSTORMS.
SIGNIFICANT SHEAR MAY ALSO SUPPORT ORGANIZED THUNDERSTORMS WITH
DAMAGING WIND POSSIBLE. THE THREAT OF SEVERE THUNDERSTORMS SHOULD
DIMINISH LATE BECAUSE OF DIMINISHED INSTABILITY ASSOCIATED WITH
PREVIOUS CONVECTION AND NOCTURNAL COOLING. THE NAM AND GFS KEEP
THE FRONT NEAR THE FORECAST AREA WEDNESDAY AND WEDNESDAY NIGHT BUT
DEEPER MOISTURE APPEARS TO SHIFT EAST OF THE AREA. THE GFS MOS
INDICATED LOWER POPS COMPARED TO THE NAM AND MAY BE CORRECT
BECAUSE OF THE DIMINISHED MOISTURE AND WIDESPREAD CONVECTION THAT
SHOULD HAVE OCCURRED EARLIER. HOWEVER...BASED ON THE FRONT
LINGERING IN THE AREA AND ANOTHER MID-LEVEL SHORTWAVE TROUGH WE
MAINTAINED CHANCE POPS. THE TEMPERATURE GUIDANCE WAS CLOSE.

&&

.LONG TERM /THURSDAY THROUGH MONDAY/...
THE GFS AND ECMWF GENERALLY SHOWED AN ONSHORE FLOW INTO THE
FORECAST AREA ASSOCIATED WITH HIGH PRESSURE CENTERED OFF THE
MIDDLE ATLANTIC COAST. THERE MAY BE A WEAKNESS IN THE UPPER
RIDGING DURING MUCH OF THE PERIOD. EXPECT SCATTERED MAINLY DIURNAL
THUNDERSTORMS WITH TEMPERATURES NEAR CLIMATOLOGY. THE GFS AND
ECMWF MOS PLUS GFS ENSEMBLE MEANS SUPPORT CHANCE POPS AND NORMAL
TEMPERATURES.

&&

.AVIATION /14Z TUESDAY THROUGH SATURDAY/...
MIX OF VFR AND MVFR EXPECTED THROUGH THE PERIOD.

WEAK LOW PRESSURE AND FRONTAL BOUNDARY WILL CONTINUE TO PROGRESS
EASTWARD AND WILL IMPACT THE TAF SITES WITH SHOWERS AND
THUNDERSTORMS LATE THIS MORNING INTO THE OVERNIGHT HOURS.
SATELLITE IMAGERY SHOWS SOME DEVELOPING CUMULUS ACROSS THE
SOUTHERN MIDLANDS AND CSRA WITH RADAR RETURNS SHOWING SCATTERED
SHOWERS ALONG AND SOUTH OF CAE/CUB. EXPECT SHOWERS AND
THUNDERSTORMS TO INCREASE IN COVERAGE AND IMPACT THE TAF
SITES...HAVE REMAINED WITH VCTS FOR THE AFTERNOON HOURS AND WILL
UPDATE AS CONFIDENCE IN TIMING INCREASES. CONVECTIVE ACTIVITY WILL
DIMINISH WITH SUNSET...HOWEVER WITH THE FRONT ACROSS THE REGION
SOME SHOWERS WILL LINGER INTO THE OVERNIGHT. POTENTIAL FOR STRATUS
AND FOG AFTER 19/06Z...HOWEVER MUCH WILL DEPEND ON TIMING OF THE
FRONT SO WILL LEAVE OUT OF TAFS ATTM.

NOTE...AGS ASOS OUT OF SERVICE. NO OBSERVATIONS WILL BE AVAILABLE
THERE FROM 05Z-11Z. NO TAF AMENDMENTS ARE SCHEDULED FOR AGS DURING
THAT TIME. AVIATION INTERESTS ARE ADVISED THAT AGS TENDS TO BE A FOG
PRONE LOCATION...ALSO OFTEN EXPERIENCING VARIABLE CONDITIONS.

EXTENDED AVIATION OUTLOOK...CHANCE OF MAINLY AFTERNOON/EVENING
THUNDERSTORMS...AS WELL AS LATE NIGHT/EARLY MORNING FOG AND STRATUS.

&&

.CAE WATCHES/WARNINGS/ADVISORIES...
SC...NONE.
GA...NONE.
&&

$$