Area Forecast Discussion
Issued by NWS Charleston, SC

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000
FXUS62 KCHS 010826
AFDCHS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
426 AM EDT SAT AUG 1 2015

.SYNOPSIS...
A STATIONARY FRONT WILL DISSIPATE OVER THE AREA THROUGH SUNDAY AS
HIGH PRESSURE BUILDS IN EARLY NEXT WEEK. AN INLAND LOW PRESSURE
TROUGH WILL THEN DEVELOP BY LATE NEXT WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
PRE-DAWN...DRY WEATHER HAS PREVAILED OVERNIGHT BUT LOW LEVEL SPEED
CONVERGENCE WAS INCREASING OVER THE COASTAL AREAS ALONG AND NORTH
OF THE SAVANNAH RIVER AND THIS SHOULD INCREASE SHOWER COVERAGE
CLOSER TO THE BEACHES AND U.S. 17 CORRIDOR NEARING DAYBREAK. A
WEAK FRONT WILL STILL BE NORTH OF FORECAST AREA EARLY THIS
MORNING WHILE THE DEEP MOISTURE OVER THE AREA PRODUCES AREAS OF
STRATUS AND STRATOCU AND EVEN PATCHY FOG IN A FEW LOCATIONS.

THE FORECAST TODAY WILL CONTINUE TO FOCUS ON THE POTENTIAL FOR
LOCALLY HEAVY RAINFALL. DEEP MOISTURE WILL PERSIST ACROSS THE
REGION BUT MODELS DO INDICATE DRIER AIR NUDGING IN FROM THE NW
LATE IN THE DAY. PWATS IN THE 2.2 TO 2.3 INCH RANGE ARE EXPECTED
TO BLANKET COASTAL AREAS AND ALL OF SE GEORGIA ALONG AND SOUTH
OF I-16. THE MESOSCALE TO START THE DAY IS QUITE COMPLEX WITH
THE DEEP MOISTURE GRADIENT TIGHTENING JUST TO THE NORTH WHILE
THE BEST DEEP LAYERED MOISTURE FLUX CONVERGENCE RESIDING TO THE
EAST OF I-95 AND ESPECIALLY ALONG IMMEDIATE COASTAL AREAS NORTH
OF THE SAVANNAH RIVER.

THROUGH THE AFTERNOON HOURS...A GOOD MODEL SIGNAL FOR LOCALLY HEAVY
CONVECTIVE RAINFALL IS THE BOUNDARY LAYER THROUGH 925 MB MOISTURE
CONVERGENCE AXIS PROGGED ALONG THE LOW LEVEL TROUGH EXTENDING
FROM SE GEORGIA TO FAR SOUTHERN SOUTH CAROLINA. STEERING FLOW IS
GENERALLY WEAK WHICH WOULD SUGGEST PLENTY OF MULTICELL CONVECTION
ON COMPLEX BOUNDARIES. A NARROW CHANNEL OF HIGH 850 MB THETA-E IS
NOTED THROUGH THIS SAME REGION WHILE A GOOD CONSENSUS OF THE MORE
RELIABLE HIGH RESOLUTION REFLECTIVITY PROGS AGREE WITH THIS
GENERAL REGION FOR A DIURNAL CONVECTION MAXIMA. WE HAVE MAINTAINED
MENTIONS FOR A FEW HOURS OF RAIN HEAVY AT TIMES FOR ALL ZONES
TOUCHING AND WEST OF I-95. SURFACE BASED INSTABILITY APPEARS BEST
OVER WESTERN ZONES WHILE MID LEVELS ALSO FAVOR THIS AREA FOR
SLIGHTLY BETTER INSTABILITY PARAMETERS AFTER 18Z. LOCALIZED
FLOODING IS CERTAINLY POSSIBLE AND WE HAVE MAINTAINED THIS IN OUR
HAZARDOUS WEATHER OUTLOOK. WE RETAINED LIKELY POPS FOR MANY AREAS.
THE CLOUDS AND LOWER CONVECTIVE TEMPS WILL KEEP TEMPS IN CHECK
WITH A GOOD CHANCE THAT MANY SOUTHERN AND EASTERN AREAS FAIL TO
REACH 90...EXCEPT NW ZONES.

TONIGHT...INLAND AREAS SHOULD SEE EVENING CONVECTION DISSIPATING
THEN A QUIET OVERNIGHT FOR THE MOST PART AS SKIES BECOME PARTLY
CLOUDY. TRICKY FORECAST ALONG COASTAL AREAS NORTH OF THE SAVANNAH
RIVER. CURRENT INDICATIONS SUGGEST WIDESPREAD CONVECTION WILL
FLARE ACROSS THE ADJACENT COASTAL WATERS WITH A FEW MODELS PUSHING
A LOW LEVEL IMPULSE ACROSS COASTAL SOUTH CAROLINA AFTER MIDNIGHT.
WE INCREASED POPS RIGHT ALONG THE COAST TO 40 PERCENT NORTH OF
EDISTO BEACH TO TREND. THERE COULD BE SOME LOWER CLOUDS AND
PATCHES OF FOG ACROSS THE AREA LATE TONIGHT AS THE WEAK FRONT
SETTLES IN FROM THE NW.

&&

.SHORT TERM /SUNDAY THROUGH TUESDAY/...
THE FRONT STALLED OVER FAR SOUTHEAST GA WILL DISSOLVE ON SUNDAY AS
THE UPPER PATTERN BECOMES ZONAL. DRIER HIGH PRESSURE WILL BUILD INTO
THE AREA FROM THE NORTHWEST THROUGH TUESDAY. PWATS EXPECTED TO DROP
BELOW 1.5" OVER MUCH OF THE AREA DURING THIS PERIOD WITH HIGHEST
VALUES REMAINING ACROSS SOUTHERN AREAS. PREVAILING ONSHORE FLOW WILL
SUPPORT A ROBUST AFTERNOON SEA BREEZE EACH DAY GIVEN HIGH TEMPS IN
THE LOW TO MID 90S. DESPITE THE DRIER LOW-LEVEL AIRMASS...MODERATE
MID-LEVEL LAPSE RATES AND THE DAILY SEA BREEZE MAY TRIGGER A FEW
SHOWERS OR TSTMS.

&&

.LONG TERM /TUESDAY NIGHT THROUGH FRIDAY/...
UPPER SHORTWAVE ENERGY WILL BEGIN MOVING INTO THE SOUTHEAST UNITED
STATES MID TO LATE WEEK WITH A PRONOUNCED SURFACE TROUGH DEVELOPING
INLAND. PWATS WILL RETURN TO A MORE TYPICAL 2" FOR EARLY AUGUST BY
THURSDAY. A COLD FRONT MAY AFFECT THE AREA FRIDAY INTO SATURDAY. WE
HAVE INCREASING POPS DURING THIS PERIOD AND SLIGHTLY MODERATED
TEMPERATURES DUE TO THICKER CLOUD COVER.

&&

.AVIATION /08Z SATURDAY THROUGH WEDNESDAY/...
OVERNIGHT...SHOWERS ARE POSSIBLE AROUND KCHS WITH MAINLY VFR
CONDITIONS AT KCHS. THE DEEP MOISTURE AT KSAV HAS RESULTED IN
STRATUS CLOUDS WHICH HAVE BEEN LOWERING CONDITIONS TO IFR AND
EVEN LIFR AT TIMES. KCHS COULD SEE SOME MVFR CIGS BREAKING OUT
FROM NEAR DAYBREAK TO MID MORNING. SHOWERS AND TSTMS ARE
ANTICIPATED ACROSS THE REGION FROM LATE MORNING THROUGH THIS
AFTERNOON...MOST NUMEROUS ALONG AND S OF I-16. DIFFICULT TO PIN
DOWN TIMING AND COVERAGE AT THIS POINT BUT HAVE TRENDED WITH TEMPO
SHOWERS AT KSAV 15Z-19Z.

EXTENDED AVIATION OUTLOOK...MOSTLY VFR. MAINLY AFTERNOON/EVENING
SHOWERS AND THUNDERSTORMS WILL IMPACT THE TERMINALS. LOW CHANCES FOR
MVFR CEILINGS OR SHALLOW FOG AROUND DAYBREAK MONDAY.

&&

.MARINE...
SYNOPTIC FLOW OVER THE WATERS WILL REMAIN SW THROUGH TONIGHT AS
THE FRONT SHOULD BE A SLOW MOVER. THE FLOW WILL INCREASE LATE
TODAY OVER THE GEORGIA WATERS AND PEAK THIS EVENING IN RESPONSE
TO A STRONG LOW LEVEL JET PUNCHING FROM NORTH FLORIDA TO THE
GULF STREAM. THERE IS A CHANCE THAT SMALL CRAFT ADVISORY
CONDITIONS DEVELOP OVER EASTERN PORTION OF THE OUTER GEORGIA
WATERS CLOSER TO THE GULF STREAM TONIGHT. GOOD LOW LEVEL JETTING
IS ANTICIPATED FROM GRAYS REEF WATERS SEAWARD WHERE 20 KT
SUSTAINED IS A GOOD BET FOR A FEW LATE TODAY THROUGH EARLY SUNDAY
MORNING. SEAS WILL BUILD TO 5 FT OFFSHORE BEYOND 20 NM.

THE WATERS WILL SEE PERIODS OF SHOWERS AND TSTMS THROUGH TONIGHT
WITH HEAVY RAINFALL REDUCING VSBYS BELOW 1 NM AT TIMES.

MAINLY SOUTH TO SOUTHWEST WINDS WILL PERSIST OVER THE WATERS INTO
MID TO LATE NEXT WEEK. THE STRONGEST WINDS WILL OCCUR AT NIGHT
DURING NOCTURNAL SURGING...THOUGH SPEEDS SHOULD GENERALLY BE 15-20
KT OR LESS. A SEA BREEZE WILL DEVELOP ALONG THE COAST EACH AFTERNOON
WITH WINDS TOPPING OUT AROUND 15 KT FOR SEVERAL HOURS. SEAS WILL
AVERAGE 2-4 FT NEARSHORE WATERS AND AS HIGH AS 4-5 FT AT TIMES OVER
THE GEORGIA OFFSHORE WATERS.

&&

.TIDES/COASTAL FLOODING...
TIDES WILL REMAIN SOMEWHAT ELEVATED TODAY INTO SUNDAY THOUGH THE
CHANCES FOR SHALLOW COASTAL FLOODING ARE DECREASING DUE TO WIND
DIRECTIONS MORE FROM THE SOUTH. TIDES IN CHARLESTON HARBOR DID NOT
REACH 7 FT FRIDAY EVENING...AN INDICATION THAT THE ANOMALY HAS BEEN
DECREASING DESPITE HIGHER ASTRONOMICAL PREDICTIONS. WILL MAINTAIN
MENTION IN THE HAZARDOUS WEATHER OUTLOOK THROUGH SUNDAY BUT IT LOOKS
LIKE CHANCES ARE DECREASING.

&&

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

&&

$$
SYNOPSIS...
NEAR TERM...JRL
SHORT TERM...JRL
LONG TERM...
AVIATION...
MARINE...JRL
TIDES/COASTAL FLOODING...



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