Areal Flood Advisory 64, NWS Columbia, SC

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE COLUMBIA SC
ISSUED BY NATIONAL WEATHER SERVICE CHARLESTON SC
408 PM EDT THU AUG 23 2012

.SYNOPSIS...
HIGH PRESSURE WILL REMAIN ACROSS THE REGION THROUGH THE
WEEKEND...BEFORE ERODING FROM THE SOUTH AS TROPICAL STORM ISAAC
MOVES TOWARD THE FLORIDA PENINSULA EARLY NEXT WEEK. MUCH OF THE
FORECAST FOR NEXT WEEK WILL BE HIGHLY DEPENDENT ON THE TRACK AND
STRENGTH OF THE TROPICAL SYSTEM.

&&

.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
A WEAK UPPER TROUGH WILL REMAIN ACROSS CENTRAL SC/GA THROUGH
TONIGHT ALTHOUGH THE BEST VORTICITY ENERGY WILL SHIFT EAST OF THE
AREA BY LATE TONIGHT. PRECIPITABLE WATER RANGES FROM 1.6 TO 1.8
INCHES THIS AFTERNOON...THUS DESPITE ONLY MODEST LOW-LEVEL
INSTABILITY AND FORCING WE ARE SEEING ISOLATED TO SCATTERED
SHOWERS DEVELOPING. THIS ACTIVITY IS EXPECTED TO DIMINISH THIS
EVENING WITH THE LOSS OF DAYTIME HEATING. MOSTLY CLOUDY SKIES WILL
PREVAIL.

&&

.SHORT TERM /6 AM FRIDAY MORNING THROUGH SUNDAY/...
A WEDGE OF SURFACE HIGH PRESSURE WILL STRETCH SOUTH/SOUTHWEST FROM
THE NEW ENGLAND STATES THROUGH THE FORECAST AREA BY FRIDAY. A WEAK
WAVE OF LOW PRESSURE WILL BE TRAVELING UP THE CAROLINA COASTLINE AT
THE SAME TIME...COINCIDENT WITH A SUBTLE UPPER LOW SHIFTING NORTH
INTO THE MID ATLANTIC STATES. SUFFICIENT CONVERGENCE AND DEEP
MOISTURE ASSOCIATED WITH THE COASTAL WAVE AND EMBEDDED ENERGY IN THE
UPPER LOW WILL WRAP INTO CENTRAL SOUTH CAROLINA...SUPPORTING A
SLIGHT CHANCE FOR SHOWERS/THUNDERSTORMS ON FRIDAY. ANY ISOLATED
CONVECTION IS EXPECTED TO DISSIPATE DURING THE EVENING HOURS WITH
THE DECREASE IN HEATING AND INSTABILITY.

AS THE WEAK LOW ALOFT CONTINUES TO DRIFT NORTHWARD AND FARTHER
FROM THE AREA...DEEP LAYER MOISTURE WILL DECREASE FOR PORTIONS OF
THE SOUTHEAST STATES. WEAK AND BROAD UPPER RIDGING WILL
PREVAIL...AND LACKING ANY NOTABLE SYNOPTIC LEVEL SUPPORT...EXPECT
PRECIPITATION POTENTIAL TO BE REDUCED FOR SATURDAY AND SUNDAY.
BOTH THE 12Z GFS AND 12Z NAM SOLUTIONS ARE RATHER DRY FOR THE
WEEKEND...AND GIVEN A BUILDING WEDGE OF HIGH PRESSURE AND THE
RESULTING LIGHT NORTHEAST FLOW...PREFER TO KEEP POPS BELOW 15
PERCENT BOTH DAYS.

CLOUD COVER WILL BE ON A DIMINISHING TREND FRIDAY THROUGH
SUNDAY...WHILE HEIGHTS ALOFT RISE WITH THE TRANSITIONING UPPER
LEVEL PATTERN. ALTHOUGH THESE FEATURES WILL USUALLY SUGGEST A
WARMING TREND...NORTHEAST FLOW SHOULD MITIGATE CONDITIONS A
BIT...RESULTING IN HIGH TEMPERATURES A DEGREE OR TWO BELOW
CLIMATOLOGICAL NORMALS. EXPECT TEMPERATURES TO PEAK IN THE UPPER
80S EACH AFTERNOON...WITH LOWS FALLING INTO THE 63 TO 68 DEGREE
RANGE EACH NIGHT.

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
MUCH OF THE EXTENDED FORECAST IS GOING TO BE HIGHLY DEPENDENT ON
IMPACTS FROM TROPICAL STORM ISAAC...AS THE SYSTEM IS EXPECTED TO
MOVE ACROSS THE FLORIDA PENINSULA EARLY NEXT WEEK. SINCE THERE IS
SIGNIFICANT UNCERTAINTY IN THE EVENTUAL TRACK AND INTENSITY OF
ISAAC...HAVE OPTED TO MAKE VERY LITTLE CHANGE TO THE ONGOING
FORECAST MONDAY AND BEYOND. A WEAKNESS IN THE BROAD UPPER RIDGE
ACROSS THE SOUTHEAST STATES COULD PROVIDE AN OPPORTUNITY FOR ISAAC
TO MOVE NORTHWARD LATE IN THE EXTENDED PERIOD. CONSIDERING A FLUX
OF MOISTURE FROM THE SOUTH...HAVE TRENDED POPS TO 20 TO 30 PERCENT
MONDAY AND TUESDAY...THEN UP TO 40 TO 50 PERCENT BY WEDNESDAY.
TEMPERATURES WILL RANGE CLOSER TO NORMAL THROUGH THE PERIOD...WITH
HIGHS IN THE UPPER 80S SUNDAY THROUGH TUESDAY AND LOWS IN THE
MIDDLE TO UPPER 60S. INCREASING CLOUD COVER WEDNESDAY SHOULD HOLD
HIGHS IN THE MIDDLE 80S WITH LOWS IN THE LOWER 70S. PLEASE REFER
TO THE LATEST ADVISORIES ON TROPICAL STORM ISAAC FROM THE NATIONAL
HURRICANE CENTER FOR THE LATEST FORECAST INTENSITY AND TRACK.

&&

.AVIATION /20Z THURSDAY THROUGH TUESDAY/...
MAINLY VFR CONDITIONS WILL PREVAIL...BUT ISOLATED SHOWERS COULD
PERIODICALLY REDUCE CONDITIONS TO MVFR LEVELS THIS AFTERNOON.
THEREFORE...HAVE INITIATED VCSH FOR ALL SITES WHILE INCLUDING A
BRIEF MVFR TEMPO AT KOGB AS DEEPER MOISTURE RESIDES ACROSS THE EASTERN
PORTION OF THE AREA. CONVECTION SHOULD DIMINISH FAIRLY QUICKLY THIS
EVENING WITH DRY CONDITIONS PREVAILING OVERNIGHT. HOWEVER...SOME
LIGHT PATCHY FOG COULD DEVELOP SEVERAL HOURS PRIOR TO SUNRISE AS
LINGERING MOISTURE BECOMES TRAPPED UNDER THE INVERSION. STILL...
CONFIDENCE REMAINS TOO LOW TO INCLUDE VISIBILITIES BELOW VFR FOR
NOW.

EXTENDED AVIATION OUTLOOK...A CHANCE OF SHOWERS AND THUNDERSTORMS...
ALONG WITH A CHANCE OF LATE NIGHT/EARLY MORNING RESTRICTIONS TO
CIGS/VSBYS...CAN BE EXPECTED THROUGH THE PERIOD.

&&

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

JRL/79/JHP

HAZARDOUS WEATHER OUTLOOK
NATIONAL WEATHER SERVICE COLUMBIA SC
ISSUED BY NATIONAL WEATHER SERVICE CHARLESTON SC
333 PM EDT THU AUG 23 2012

GAZ040-063>065-077-SCZ015-016-018-020>022-025>031-035>038-041-241945-
LINCOLN-MCDUFFIE-COLUMBIA-RICHMOND-BURKE-LANCASTER-CHESTERFIELD-
MCCORMICK-NEWBERRY-FAIRFIELD-KERSHAW-EDGEFIELD-SALUDA-LEXINGTON-
RICHLAND-LEE-AIKEN-SUMTER-BARNWELL-ORANGEBURG-CALHOUN-CLARENDON-
BAMBERG-
333 PM EDT THU AUG 23 2012

THIS HAZARDOUS WEATHER OUTLOOK IS FOR EAST CENTRAL GEORGIA AND
CENTRAL SOUTH CAROLINA.

.DAY ONE...THIS AFTERNOON AND TONIGHT.

SCATTERED SHOWERS AND ISOLATED THUNDERSTORMS WILL REMAIN POSSIBLE
THROUGH THIS EVENING. TORRENTIAL RAINFALL MAY PRODUCE LOCALIZED
FLOODING.

.DAYS TWO THROUGH SEVEN...FRIDAY THROUGH WEDNESDAY.

THE PROBABILITY FOR WIDESPREAD HAZARDOUS WEATHER IS LOW.

.SPOTTER INFORMATION STATEMENT...

SPOTTER ACTIVATION IS NOT EXPECTED AT THIS TIME.

SPECIAL WEATHER STATEMENT
NATIONAL WEATHER SERVICE COLUMBIA SC
ISSUED BY NATIONAL WEATHER SERVICE CHARLESTON SC
254 PM EDT THU AUG 23 2012

GAZ065-077-SCZ029>031-035>038-041-232100-
RICHMOND-BURKE-LEE-AIKEN-SUMTER-BARNWELL-ORANGEBURG-CALHOUN-
CLARENDON-BAMBERG-
INCLUDING THE CITIES OF...AUGUSTA...HEPHZIBAH...WAYNESBORO...
BISHOPVILLE...SAVANNAH RIVER SITE...AIKEN...NORTH AUGUSTA...
SUMTER...BARNWELL...WILLISTON...BLACKVILLE...ORANGEBURG...
ST. MATTHEWS...MANNING...SUMMERTON...BAMBERG...DENMARK
254 PM EDT THU AUG 23 2012

...LOCALLY HEAVY RAINFALL POSSIBLE THIS AFTERNOON...

SCATTERED SHOWERS AND THUNDERSTORMS WILL CONTINUE TO DEVELOP
ACROSS PARTS OF THE SOUTHERN MIDLANDS OF SOUTH CAROLINA AS WELL AS
THE CENTRAL SAVANNAH RIVER AREA OF EASTERN GEORGIA THROUGH THE
REMAINDER OF THE AFTERNOON HOURS. ANY THUNDERSTORMS THAT DEVELOP
WILL BE SLOW MOVING AND CAPABLE OF PRODUCING TORRENTIAL
DOWNPOURS. LOCALIZED RAINFALL AMOUNTS IN EXCESS OF 2 INCHES COULD
OCCUR UNDER WHICH MAY RESULT IN MINOR FLOODING OF LOW LYING AND
POOR DRAINAGE AREAS.

STAY TUNED TO NOAA WEATHER RADIO ALL HAZARDS...TV OR YOUR LOCAL
NEWS SOURCE FOR THE LATEST WEATHER INFORMATION AND POSSIBLE FLOOD
ADVISORIES FROM THE NATIONAL WEATHER SERVICE.