Area Forecast Discussion
Issued by NWS Charleston, SC

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000
FXUS62 KCHS 030547
AFDCHS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
147 AM EDT MON AUG 3 2015

.SYNOPSIS...
A WEAK LOW PRESSURE WILL LIFT NORTHEASTWARD ALONG A SURFACE TROUGH
THROUGH MONDAY NIGHT AS A STATIONARY FRONT REMAINS WELL INLAND.
HIGH PRESSURE WILL BUILD IN TUESDAY AND WEDNESDAY BEFORE AN INLAND
TROUGH OF LOW PRESSURE DEVELOPS THURSDAY. A COLD FRONT WILL DROP
INTO THE AREA NEXT WEEKEND.

&&

.NEAR TERM /UNTIL 6 AM THIS MORNING/...
THE BROAD CYCLONIC FLOW INDUCED BY THE SURFACE LOW ALONG THE
FLORIDA BIG BEND WILL SUPPORT INCREASING NOCTURNAL SPEED
CONVERGENCE ALONG THE GEORGIA AND LOWER SOUTH CAROLINA COAST
OVERNIGHT AS NOCTURNAL JETTING TAKES HOLD ALONG THE WESTERN WALL
OF THE STREAM. CONVECTIVE RAINS CONTINUE ALONG COASTAL ZONES
ALONG AND E OF I-95 THIS MORNING. HIGH ATMOSPHERIC MOISTURE
CHARACTERIZED BY A RIBBON OF PWATS 2.10-2.30 INCHES WILL SUPPORT
CONTINUED PERIODS OF SHOWERS AND A FEW TSTMS OVERNIGHT ACROSS
THE EASTERN HALF OF THE FORECAST AREA WITH LOCALIZED DOWNPOURS AT
TIMES...ESPECIALLY SOUTH CAROLINA ZONES WHERE CONVERGENCE IS
GREATEST.

LOWS WILL RANGE FROM THE LOWER-MID 70S INLAND WITH UPPER 70S/NEAR
80 AT THE BEACHES/DOWNTOWN CHARLESTON.

&&

.SHORT TERM /6 AM THIS MORNING THROUGH WEDNESDAY/...
MONDAY AND MONDAY NIGHT...SIGNIFICANT CHANGES WERE MADE TO THE
FORECAST AS MODELS HAVE TRENDED MUCH WETTER THROUGH MONDAY NIGHT.
THE MAIN CAUSE OF THIS TREND IS THE WEAK AREA OF LOW PRESSURE
CURRENTLY NEAR THE BIG BEND OF FLORIDA THAT IS FORECAST TO LIFT
NORTHEASTWARD ALONG A STALLED FRONT. AS THIS OCCURS...A DEEP SOUTH
TO SOUTHEAST MOISTURE FEED WILL BECOME ENHANCED AHEAD OF THE SURFACE
LOW AND INTO COASTAL SOUTHEAST SOUTH CAROLINA AND SOUTHEAST GEORGIA.
THE PERCENT OF NORMAL PRECIPITABLE WATER SATELLITE PRODUCT CURRENTLY
SHOWS VALUES IN THE 120-130 PERCENT RANGE NEAR THE LOW...AND THIS
AIRMASS WILL BECOME SOLIDLY ENTRENCHED ACROSS THE FORECAST AREA
BEGINNING MONDAY MORNING. SUCH PERCENT OF NORMAL VALUES POINT TO
PWATS ON THE ORDER OF 2.25 INCHES FOR MUCH OF THE DAY ON MONDAY AND
INTO MONDAY NIGHT. THE MODELS...ESPECIALLY THE 02/12Z ECMWF...PUT
THE QPF BULLSEYE RIGHT ON THE FORECAST AREA AND MAINLY ALONG THE
SOUTH CAROLINA COAST. THIS SEEMS QUITE REASONABLE GIVEN THE DEGREE
OF MOISTURE...PRESENCE OF A LOW LEVEL FEATURE...AND EVEN SOME
UPPER LEVEL DIVERGENCE IN THE ENTRANCE OF A 250-300 MB JET. POPS
HAVE BEEN INCREASED INTO THE 60 PERCENT RANGE FOR MAINLY THE TRI-
COUNTY REGION...AND THIS MAY NEED TO BE EXPANDED DEPENDING ON HOW
PRECIPITATION EVOLVES OVERNIGHT INTO MONDAY MORNING.
OVERNIGHT...THE LOW WILL BEGIN TO LIFT NORTHEASTWARD AND THE AXIS
OF DEEPER MOISTURE AND BEST COVERAGE WILL SHIFT UP TOWARD THE
NC/SC BORDER. HAVE MAINTAINED AT LEAST CHANCE POPS ACROSS THE EAST
UNTIL A MORE DEFINITIVE TREND CAN BE IDENTIFIED. TEMPERATURES FOR
MONDAY WILL BE TRICKY AS AREAS ALONG AND EAST OF I-95 WILL LIKELY
SEE LITTLE TO NO DIRECT SUNLIGHT. THIS COULD KEEP HIGHS DOWN
SIGNIFICANTLY...WITH STILL LOW 90S POSSIBLE ACROSS INTERIOR
SOUTHEAST GEORGIA.

TUESDAY THROUGH WEDNESDAY...MUCH DRIER DEEP LAYER AIR WILL WORK INTO
THE AREA AND POPS ARE NO MORE THAN 20 PERCENT AS HIGH PRESSURE
BUILDS IN BEHIND THE DEPARTING SURFACE WAVE. WARM TEMPERATURES WILL
RETURN...WITH HIGHS REACHING THE MID TO UPPER 90S AWAY FROM THE
IMMEDIATE COAST.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH SUNDAY/...
A RELATIVELY WET PATTERN IS ANTICIPATED WEDNESDAY NIGHT THROUGH
SUNDAY AS A LONGWAVE TROUGH TAKES SHAPE IN THE UPPER LEVELS. A
PRONOUNCED LEE TROUGH WILL DEVELOP LATE WEEK...THEN A COLD FRONT
WILL DROP INTO THE AREA OVER THE WEEKEND. PWATS SURGE BACK ABOVE 2"
LATE WEEK WITH VALUES APPROACHING 2.3" SATURDAY AND SATURDAY NIGHT.
WE SHOW INCREASING POPS DURING MUCH OF THE PERIOD...ESPECIALLY
DURING DAYTIME HOURS. TEMPERATURES WILL BE MODERATED BY LOWER
HEIGHTS AND GREATER CLOUD COVER...THUS HIGHS WILL MAINLY REACH NO
HIGHER THAN THE LOWER 90S.

&&

.AVIATION /06Z MONDAY THROUGH FRIDAY/...
KCHS...IT APPEARS THAT THE INITIAL SURGE OF MOISTURE ADVECTION
AND CONVERGENCE IS WANING AND CHANCES FOR ADDITIONAL SIGNIFICANT
RAINS OVERNIGHT ARE DIFFICULT TO PIN DOWN ALTHOUGH THE PATTERN
SEEMS PRIMED FOR ADDITIONAL ACTIVITY BEFORE DAWN. MODELS PAINTING
UNSETTLED CONDITIONS DURING THE FIRST HALF OF THE DAY WITH PLENTY
OF SHOWERS AND A FEW TSTMS. MVFR CIGS AND VSBYS POSSIBLE THROUGH
LATER THIS AFTERNOON.

KSAV...MAINLY LIGHT SHOWER ACTIVITY OVERNIGHT WITH PERIODS OF
MVFR CIGS...BECOMING MORE LIKELY NEARING DAYBREAK. AFTER DAWN...
PERIODS OF SHOWERS AND A FEW TSTMS COULD IMPACT THE TERMINAL
THROUGH EARLY AFTERNOON WITH REDUCING CIGS AND VSBYS AT TIMES.
IMPROVING CONDITIONS BY THIS EVENING AS DEEPER MOISTURE EASES
OFFSHORE.

EXTENDED AVIATION OUTLOOK...ELEVATED CHANCES OF DIRECT IMPACTS
FROM SHOWERS AND THUNDERSTORMS MONDAY EVENING...ESPECIALLY AT
KCHS.

&&

.MARINE...
OVERNIGHT...A WEAK AREA OF LOW PRESSURE NEAR THE FLORIDA BIG BEND
AREA WILL MOVE NORTHEAST INTO SOUTHEAST GEORGIA. THIS WILL PLACE
THE TIGHTEST PRESSURE GRADIENT/LOW-LEVEL JET MAINLY BEYOND 20 NM
AND THIS IS WHERE WE HAVE RAISED A SMALL CRAFT ADVISORY. ACROSS
THE NEAR SHORE WATERS SOUTHERLY WINDS WILL SURGE BUT REMAIN MAINLY
20 KT OR LESS WITH SEAS BUILDING UP TO 4 FT.

MONDAY THROUGH FRIDAY...A WEAK AREA OF LOW PRESSURE WILL MOVE
NORTHEASTWARD ALONG THE COAST THROUGH TUESDAY. HIGH PRESSURE WILL
THEN RETURN WITH A TROUGH OF LOW PRESSURE INLAND...WITH ANOTHER
FRONT REACHING THE AREA LATE IN THE WEEK. THIS SETUP WILL RESULT IN
A PREVAILING SOUTHWEST FLOW ACROSS THE WATERS THROUGH THE
WEEK...WITH VARIOUS PERIODS OF ENHANCED FLOW AS THE PRESSURE
GRADIENT TIGHTENS. WINDS WILL GENERALLY TOP OUT IN THE 15-20 KT
RANGE WITH SOME POTENTIAL FOR GUSTS TO AROUND 25 KT AT
TIMES...MAINLY OVER THE OUTER GEORGIA WATERS. SEAS WILL BE ELEVATED
THROUGH MUCH OF THE WEEK...ESPECIALLY MONDAY THROUGH TUESDAY NIGHT.
A SMALL CRAFT ADVISORY WILL BE IN EFFECT FOR THE OUTER GEORGIA
WATERS THROUGH MIDDAY TUESDAY TO ACCOUNT FOR 6 FT SEAS.
OTHERWISE...SEAS WILL BE 2-4 FT OUT TO 20 NM...AND 5 FT BEYOND.

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
SC...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL NOON EDT TUESDAY FOR AMZ374.

&&

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


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