Area Forecast Discussion
Issued by NWS Charleston, SC

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000
FXUS62 KCHS 031138
AFDCHS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
738 AM EDT THU SEP 3 2015

.SYNOPSIS...
AN AREA OF LOW PRESSURE WILL MOVE OFF THE GEORGIA COAST TODAY. A
WEAK TROUGH OF LOW PRESSURE WILL PERSIST OVER THE SOUTHEAST FRIDAY
AND FRIDAY NIGHT. A COLD FRONT WILL CROSS THE REGION FROM NORTH TO
SOUTH SATURDAY...AND HIGH PRESSURE WILL BUILD INTO THE AREA FROM
THE NORTH. THE FRONT WILL BECOME STATIONARY SOUTH OF THE
REGION...AND LOW PRESSURE COULD DEVELOP OFF THE SOUTHEAST COAST.
THE REGION WILL THEN REMAIN SITUATED BETWEEN INLAND HIGH PRESSURE
AND OFFSHORE LOW PRESSURE UNTIL THE MIDDLE OF NEXT WEEK.
THEN...ATLANTIC HIGH PRESSURE WILL EXPAND INTO THE REGION FROM THE
EAST.

&&

.NEAR TERM /THROUGH TONIGHT/...
NEAR-DAWN...THE REMNANT EDDY FROM ERIKA HAS MOVED OFF THE GEORGIA
COAST AROUND SAINT SIMONS ISLAND. DEEP CONVECTION HAS BEEN
CONFINED TO THE WATERS OVERNIGHT BUT ENOUGH CONVERGENCE DEVELOPED
FROM THE RESULT OF THE LAND BREEZE AND MESOSCALE BOUNDARIES TO
PRODUCE ISOLATED TO SCATTERED LOWER-TOPPED SHOWERS WITH LOCALLY
HEAVY DOWNPOURS FROM HILTON HEAD ISLAND SOUTH TO THE GEORGIA
BARRIER ISLANDS. FOG DEVELOPMENT OCCURRED RIGHT ALONG AND SOUTH
OFT THE ALTAMAHA RIVER AREA.

MODEL FORECAST SOUNDINGS ALONG WITH 700 MB AND 500 MB PROGS BOTH
SUGGEST GENERAL MID LEVEL SUBSIDENCE MOVING INTO THE FORECAST AREA
THROUGH EARLY AFTERNOON IN THE WAKE OF BOTH THE SHORT WAVE OFF
THE MID ATLC COAST AND THE WEAK LOW PASSING OFF THE GEORGIA COAST.
WEAK MID MID LEVEL PERTURBATIONS WILL THEN APPROACH FROM THE NW
LATE DAY AND THIS EVENING. THIS MORNING...THE BEST CHANCES FOR
SHOWERS WILL BE ALONG THE SE GEORGIA COAST WHERE THE DEEPER
MOISTURE RESIDES AND THE SLOWLY EJECTING LOW EASES ON. LOW CLOUDS
AND PATCHY FOG POSSIBLE EARLY ON OVER INLAND AREAS SHOULD
DISSIPATE WELL BEFORE LATE MORNING ALLOWING TEMPS TO RISE INTO THE
UPPER 80S TO LOWER 90S BY THE EARLY AFTERNOON. HIGHS LOWER TO MID
90S BUT POTENTIAL FOR DEW POINT POOLING DOES NOT LOOK IMPRESSIVE
THIS AFTERNOON...HEAT INDICES NEAR 100 DEGREES.

A FAIRLY DECENT LOOKING MID LEVEL ENVIRONMENT THIS AFTERNOON
SHOULD BE CAPPED OFF INITIALLY BY THE MIDDAY SUBSIDENCE REGIME.
ISOLATED TO LOCALLY SCATTERED AFTERNOON AND EVENING SHOWERS
AND TSTMS ARE EXPECTED OVER AREAS MAINLY INLAND FROM U.S. 17
TODAY WITH A FEW OF THE TSTMS PERHAPS DRIFTING TOWARD THE COAST
LATE. MOST OF THE CONVECTION SHOULD BE PULSE WITH A LOW-END
POTENTIAL FOR A COUPLE OF STRONGER STORMS LATER TODAY. WE CAPPED
POPS AT 30 PERCENT. COVERAGE SHOULD WANE SHORTLY AFTER SUNSET
BUT CANNOT RULE OUT AN ISOLATED SHOWER OR TSTM DURING THE EVENING
AS SOME WEAK UPPER DIFLUENCE RIPPLES PAST THE AREA. OVERNIGHT...
PARTLY CLOUDY SKIES SHOULD PREVAIL WITH PATCHY FOG MOST LIKELY
WELL INLAND.

&&

.SHORT TERM /FRIDAY THROUGH SUNDAY/...
FRIDAY...EXPECT A HOT DAY AHEAD OF AN APPROACHING COLD FRONT. AWAY
FROM THE BEACHES...HIGHS IN THE MID/UPPER 90S WILL PREVAIL...AND
MAXIMUM AFTERNOON HEAT INDEX VALUES 100-105F SHOULD BE COMMON.
DESPITE THE ABOVE-NORMAL TEMPERATURES...RECORD HIGH TEMPERATURES ARE
NOT IN JEOPARDY FRIDAY. MEANWHILE...THE 03/00Z GFS DEPICTS A
WARM/CAPPED ENVIRONMENT ALOFT...RESULTING IN RATHER WEAK INSTABILITY
AND SUPPORTING NOTHING MORE THAN SPARSE/BRIEF COVERAGE OF ANY
DIURNAL SHOWERS/THUNDERSTORMS ALONG THE SEA BREEZE/ALONG AN INLAND
TROUGH OF LOW PRESSURE.  ON THE OTHER HAND...THE 03Z NAM AND EURO
DEPICT STRONGER INSTABILITY AND SUFFICIENT SHEAR TO SUPPORT BETTER
COVERAGE OF MULTICELL SHOWERS/ THUNDERSTORMS...EVEN SUPPORTING A
POTENTIAL FOR AN ISOLATED/BRIEF PULSE THUNDERSTORM OR TWO DURING THE
AFTERNOON HOURS. THE LATEST FORECAST DEPICTS SLIGHT CHANCE/CHANCE
POPS DURING FRIDAY AFTERNOON.

LATER FRIDAY NIGHT...A COLD FRONT WILL PUSH INTO NORTHERN COUNTIES
OF THE FORECAST AREA FROM THE EAST/NORTHEAST. WHILE SLIGHT
CHANCE/CHANCE POPS ARE JUSTIFIED THROUGH THE NIGHT/AHEAD OF THE
FRONT...THE ARRIVAL OF THE FRONT DURING THE MOST STABLE PART OF THE
DAY SUGGESTS THE POTENTIAL FOR LIMITED RAIN COVERAGE.
OTHERWISE...TEMPERATURES WILL REMAIN WELL INTO THE 70S AHEAD OF THE
FRONT.

THE COLD FRONT WILL ADVANCE THROUGH THE FORECAST SATURDAY...AND HIGH
PRESSURE WILL BUILD INTO THE REGION FROM THE NORTH. THE FRONT SHOULD
PRODUCE AT LEAST ISOLATED/SCATTERED THUNDERSTORMS. SINCE DRIER AIR
IS PROGGED TO PUSH INTO THE REGION FROM THE NORTHEAST SATURDAY
AFTERNOON...HIGHEST POPS OF 40-50 PERCENT ARE PLACED ALONG/WEST OF
INTERSTATE 95 SATURDAY AFTERNOON. OTHERWISE...SATURDAY
HIGH TEMPERATURES SHOULD AVERAGE 5-8F COOLER THAN THOSE OF FRIDAY.

SATURDAY NIGHT...SCATTERED EVENING SHOWERS/THUNDERSTORMS MAINLY OVER
SOUTHERN/INLAND COUNTIES SHOULD BECOME CONFINED TO THE CENTRAL/SOUTHERN
COAST AND ADJACENT WATERS AS A LONG FETCH NE FLOW DEVELOPS BETWEEN
HIGH PRESSURE TO THE NORTH AND A STATIONARY FRONT/ASSOCIATED
TROUGH AND AREA OF LOW PRESSURE TO THE SOUTH. LOW TEMPS 70-75 ARE
EXPECTED...HIGHEST NEAR THE COAST.

SUNDAY...MODELS DISAGREE WHETHER A POCKET OF RELATIVELY DRY 850-500
MB AIR WILL REMAIN OVER THE REGION OR OF DEEPER MOISTURE WILL SPILL
ONSHORE FROM THE EAST/NORTHEAST. THIS FORECAST ASSUMES THAT
SUFFICIENT MOISTURE WILL PUSH INTO THE REGION TO SUPPORT SCATTERED
SHOWERS AND PERHAPS ISOLATED THUNDERSTORMS. OTHERWISE...EXPECT
PLENTY OF CLOUDS AND BELOW-NORMAL TEMPERATURES IN THE LOWER/MID 80S
MOST AREAS.

&&

.LONG TERM /SUNDAY NIGHT THROUGH WEDNESDAY/...
A BLOCKING PATTERN WILL MAINTAIN SURFACE HIGH PRESSURE TO THE
NORTH...A STATIONARY FRONT WEAKENING TO A TROUGH OF LOW PRESSURE
SOUTH/SOUTHEAST OF THE AREA...A BROAD AREA OF SURFACE LOW PRESSURE
OFF THE SOUTHEAST COAST AND BROAD LOW PRESSURE ALOFT OVER THE
SOUTHEAST. LABOR DAY INTO TUESDAY...LONG FETCH ONSHORE FLOW ENHANCED
BY SURFACE FEATURES AND THE UPPER LOW/POOL OF VORTICITY ALOFT SHOULD
PROVIDE SUFFICIENT MOISTURE/INSTABILITY TO SUPPORT AT LEAST
SCATTERED SHOWERS/ISOLATED THUNDERSTORMS DURING THE DAYTIME HOURS
ACROSS THE REGION...AND POPS ARE EXPECTED TO REFOCUS CLOSER TO THE
COAST AND ACROSS ADJACENT COASTAL WATERS DURING THE NIGHTTIME HOURS.
CAPPED MAXIMUM POPS AT 50 PERCENT THROUGH THE PERIOD...ALTHOUGH
LOCALLY WETTER PERIODS/HIGHER POPS ARE POSSIBLE ESPECIALLY NEAR THE
COAST. TEMPERATURES IN THE LOWER 80S ON THE BEACHES AND MID 80S
INLAND ARE EXPECTED LABOR DAY...THEN TEMPERATURES SHOULD MODERATE
INTO THE MID/UPPER 80S INLAND TUESDAY. BY THE MIDDLE OF NEXT WEEK
THROUGH THE END OF THIS FORECAST PERIOD...INLAND HIGH PRESSURE AND
OFFSHORE LOW PRESSURE WILL WEAKEN...THE UPPER LOW/TROUGH AXIS WILL
RETROGRADE WEST OF THE REGION AND ATLANTIC HIGH PRESSURE WILL EXPEND
INTO THE REGION FROM THE EAST. THIS SCENARIO SHOULD SUPPORT A TREND
TOWARD WARMER/ABOVE NORMAL TEMPS AND SLIGHTLY LOWER POPS.

&&

.AVIATION /12Z THURSDAY THROUGH MONDAY/...
VFR CONDITIONS ARE EXPECTED AT BOTH KCHS AND KSAV TERMINALS
THROUGH 12Z THURSDAY. HOWEVER...THERE REMAINS A CHANCE OF MVFR OR
LOWER CONDITIONS ALONG WITH VCSH AT THE KSAV TERMINAL UNTIL 14Z.
THERE COULD BE A FEW AFTERNOON OR EARLY EVENING TSTMS NOT TOO FAR
WEST OF THE TERMINALS THIS AFTERNOON BUT CHANCES APPEAR TOO LOW AT
THIS POINT FOR ANY VCTS/CB MENTIONS.

EXTENDED AVIATION OUTLOOK...THROUGH MONDAY... OUTSIDE ANY
SHOWERS/THUNDERSTORMS...MAINLY VFR FRIDAY AND FRIDAY NIGHT. THE
PROBABILITY FOR PERIODS OF FLIGHT RESTRICTIONS...MAINLY WITHIN LOWER
CEILINGS AND/OR SHOWERS...WILL INCREASE THIS WEEKEND INTO EARLY NEXT
WEEK.

&&

.MARINE...
THE REMNANT LOW FROM THE CAPE VERDE BORN ERIKA HAS MOVED OFF THE
COAST THIS MORNING JUST SOUTH OF THE ALTAMAHA RIVER. DEEP
MOISTURE WAS PILING UP JUST ALONG AND OFF THE SOUTH GEORGIA COAST.
SHOWERS AND TSTMS WILL BE NUMEROUS THIS MORNING OVER THE SOUTHERN
SOUTH CAROLINA AND GEORGIA WATERS WHILE THE LOW MOVES OFFSHORE.
HEAVY RAINS WILL LOCALLY THERE ARE FAVORABLE CONDITIONS FOR
WATERSPOUT DEVELOPMENT THIS MORNING AND WE HAVE ISSUED A MARINE
WEATHER STATEMENT.

GENERALLY ANOTHER FAIRLY TRANQUIL PERIOD THROUGH TONIGHT AS
A WEAK SURFACE MOVES LATE BY EARLY FRIDAY. WINDS WILL BE 10 KT
OR LESS ON AVERAGE AND SEAS 2 FT OR LESS. WAVES COULD BE UP TO
3 FT SEAWARD FROM GRAYS REEF TODAY.

FRIDAY THROUGH TUESDAY...THE ONGOING WEAK PRESSURE PATTERN WILL
PREVAIL ACROSS THE WATERS FRIDAY THROUGH AT LEAST FRIDAY EVENING.
THIS WILL KEEP WINDS NO HIGHER THAN 10-15 KT ALONG THE LAND/SEA
INTERFACE WITH THE FRIDAY AFTERNOON SEA BREEZE AND LESS THAN 10 KT
THROUGH MUCH OF FRIDAY NIGHT. SEAS WILL REMAIN 1-2 FT THROUGH THIS
PERIOD. LATE FRIDAY NIGHT OR EARLY SATURDAY...A COLD FRONT WILL
ENTER NORTHERN WATERS AND WILL PUSH SOUTH OF GA WATERS BY LATER
SATURDAY. BEHIND THIS FRONT...STRONG HIGH PRESSURE WILL BUILD IN
FROM THE NORTH AND A TIGHTENING NORTHEAST GRADIENT WILL PREVAIL.
THIS SETUP WILL RESULT IN INCREASING WINDS AND SEAS. AT THIS TIME
IT APPEARS WINDS WILL PEAK IN THE 15-20 KT RANGE WITH SEAS
BUILDING TO 2 TO 4 FT...HIGHEST BEYOND 20 NM. THERE IS A LOW
PROBABILITY FOR SMALL CRAFT CONDITIONS SATURDAY NIGHT THROUGH
LABOR DAY...ESPECIALLY IF LOW PRESSURE SOUTHEAST OF THE WATERS
ENHANCES THE ONSHORE GRADIENT. THE GRADIENT COULD BEGIN TO RELAX
AND WINDS/SEAS COULD BEGIN TO IMPROVE BY TUESDAY.

RIP CURRENTS...AN ELEVATED RISK FOR RIP CURRENTS COULD DEVELOP AGAIN
OVER THE UPCOMING HOLIDAY WEEKEND. WILL BEGIN TO ADDRESS THIS
POTENTIAL WITHIN THE THURSDAY MORNING HAZARDOUS WEATHER OUTLOOK.

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
SC...NONE.
MARINE...NONE.

&&

$$
SYNOPSIS...
NEAR TERM...
SHORT TERM...SPR
LONG TERM...SPR
AVIATION...
MARINE...SPR


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