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Area Forecast Discussion
Issued by NWS Columbia, SC

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000
FXUS62 KCAE 210720
AFDCAE

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE COLUMBIA SC
320 AM EDT TUE MAY 21 2013

.SYNOPSIS...
HIGH PRESSURE OFF THE SOUTHEAST COAST WILL CIRCULATE A MOIST
SOUTHERLY FLOW INTO THE FORECAST AREA AHEAD OF A SLOW MOVING COLD
FRONT THROUGH THURSDAY. THE COLD FRONT WILL MOVE THROUGH THE AREA
THURSDAY NIGHT. THE DRY AIR MASS BEHIND THE FRONT WILL DOMINATE
DURING THE WEEKEND.

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
HIGH PRESSURE RIDGING INTO THE FORECAST AREA FROM THE ATLANTIC
WILL DOMINATE TODAY. A MOIST SOUTH FLOW IS ASSOCIATED WITH THIS
FEATURE. THE HIGH LOW-LEVEL MOISTURE WILL SUPPORT STRATUS AND
AREAS OF FOG EARLY THIS MORNING. THE MOISTURE PLUS HEATING SHOULD
SUPPORT SCATTERED THUNDERSTORMS THIS AFTERNOON. EXPECT THE GREATER
THUNDERSTORM COVERAGE IN THE EAST PART CLOSER TO THE TROPICAL
PLUME OF MOISTURE SHOWN BY THE WATER VAPOR IMAGERY. CONVERGENCE
ASSOCIATED WITH THE SEA-BREEZE FRONT SHOULD ALSO AID COVERAGE IN
THE EAST PART. CLOUDINESS SHOULD LIMIT INSTABILITY. THE NAM
GENERALLY INDICATES WEAK TO MODERATE INSTABILITY AND WEAK SHEAR.
THE THREAT OF SEVERE THUNDERSTORMS APPEARS LOW AT THIS TIME. THE
GUIDANCE CONSENSUS SUPPORTS HIGHS IN THE MIDDLE 80S WHICH IS NEAR
CLIMATOLOGY.

.SHORT TERM /6 PM THIS EVENING THROUGH THURSDAY NIGHT/...
THE HIGH OFF THE SOUTHEAST COAST WILL CONTINUE TO DOMINATE
THROUGH WEDNESDAY NIGHT. THE MODELS SHOW CONSIDERATE MOISTURE IN
THE SOUTHERLY FLOW ON THE BACKSIDE OF THE OFFSHORE HIGH. EXPECT
SCATTERED THUNDERSTORMS ESPECIALLY DURING THE TIME OF MAXIMUM
HEATING. THE GUIDANCE CONSENSUS SUPPORTS CHANCE POPS. ALSO USED
THE CONSENSUS FOR THE TEMPERATURE FORECAST.

.LONG TERM /FRIDAY THROUGH MONDAY/...
CONVERGENCE ASSOCIATED WITH THE SLOW MOVING COLD FRONT SUPPORTS
THUNDERSTORMS THURSDAY AND THURSDAY NIGHT BUT THE MODELS SHOW
DEEPER MOISTURE SHIFTING FARTHER EASTWARD AHEAD OF THE FRONT. THE
GFS ENSEMBLE MEAN PLUS OPERATIONAL GFS AND ECMWF MOS SUPPORT
CHANCE POPS. THE DRY AIR MASS BEHIND THE FRONT SHOULD DOMINATE
DURING THE REST OF THE MEDIUM-RANGE PERIOD.

.AVIATION /07Z TUESDAY THROUGH SATURDAY/...
-- Changed Discussion --LOW CLOUDS HAVE DEVELOPED OVER MUCH OF THE AREA EARLY THIS MORNING.
CIGS MOSTLY IN THE IFR/LIFR RANGE...ALTHOUGH AGS/DNL REMAIN VFR.
CAE VWP INDICATING 25-30 KT LOW-LEVEL JET. LIGHT TO CALM WINDS
OVERNIGHT WILL ALLOW SOME RADIATIONAL COOLING AND EXPECT SOME FOG
TO DEVELOP DURING THE PRE- DAWN HOURS...BUT CONFIDENCE IS LOW AT
THIS TIME AS TO HOW LOW CIGS WILL GO. ANY FOG AND LOW STRATUS
SHOULD DISSIPATE BY 14Z WITH VFR CONDITIONS EXPECTED FOR THE
REMAINDER OF THE PERIOD. WINDS WILL PICK UP OUT OF THE SOUTH TO
SOUTHEAST AROUND 5-7 KNOTS. WIDELY SCTD CONVECTION POSSIBLE LATER
THIS AFTERNOON BUT NOT ENOUGH CONFIDENCE TO MENTION AT ANY OF THE
TAF SITES AT THIS TIME. MODEL DATA SEEMS TO INDICATE THAT BULK OF
CONVECTION THAT MAY DEVELOP LATER THIS AFTERNOON MAY BE EAST OF
THE TAF SITES.

EXTENDED AVIATION OUTLOOK...SCATTERED SHOWERS AND
THUNDERSTORMS...MAINLY AFTERNOON AND EVENING...POSSIBLE THROUGH
FRIDAY. LATE NIGHT/EARLY MORNING FOG/STRATUS ALSO POSSIBLE.-- End Changed Discussion --

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

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