Area Forecast Discussion
Issued by NWS Charleston, SC

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000
FXUS62 KCHS 300809
AFDCHS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
409 AM EDT WED JUL 30 2014

.SYNOPSIS...
A STATIONARY FRONT WILL REMAIN OFFSHORE THROUGH THURSDAY. THE FRONT
WILL THEN WEAKEN AND MOVE BACK TOWARD THE COAST AS A SURFACE TROUGH
FRIDAY THROUGH EARLY NEXT WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
CLEAR TO PARTLY CLOUDY SKIES ACROSS THE REGION WITH MORNING WITH POCKETS
OF MID LEVEL CLOUDINESS ASSOCIATED WITH DUAL AREAS OF MID LEVEL VORTICITY
SLIDING THROUGH THE CAROLINAS. THERE HAS BEEN ISOLATED SHOWERS NEAR
THE ALTAMAHA RIVER AREA OVERNIGHT BUT MAINLY SOUTH OF BOTH THE RIVER
AND OUR FORECAST AREA. CANNOT COMPLETELY RULE OUT A NEAR COASTAL SHOWER
IN SE GEORGIA BUT THE DAY SHOULD BEGIN DRY WITH TEMPS IN THE 60S INLAND
TO LOWER 70S NEARING THE COAST.

A SUBTLE WEDGE PATTERN WILL DEVELOP THROUGH TONIGHT IN THE WAKE OF THE
WEAK SHORT WAVE PASSING OFFSHORE AND HIGH PRES BUILDING OVER THE COASTAL
MID ATLC REGION. THE SURFACE FLOW WILL TURN ONSHORE THIS AFTERNOON
ALONG COASTAL AREAS. WEAK DEEP LAYERED INSTABILITY AND SEASONABLY
LOW PWATS SUGGEST A MAINLY DRY DAY MOST AREAS BUT THE MODELS ALL
PRODUCE SPOTTY FIELDS OF LIGHT CONVECTIVE QPF ALONG AND E OF I-95
THIS AFTERNOON AND EARLY EVENING WHICH GENERALLY SEEMS OVERDONE.
FORECAST SOUNDINGS INDICATE A STRONG SUBSIDENCE CAP BETWEEN 600
AND 700 MB WHICH WOULD MAKE FOR A VERY SLIM DEEP CONVECTION POTENTIAL.
A FEW SHOWERS COULD CROP UP WHERE MOISTURE CONVENES IN THE LOWER
LEVELS WITH THE SEA BREEZE. WE SHOW A SLIGHT CHANCE OF A SHOWER
BUT CHANCES NOT REACHING 20 PERCENT IN ANY GIVEN LOCATION AT THIS
POINT. LOW LEVEL THICKNESS PROGS INDICATE LOWER 90S MAX TEMPS BUT
A FEW OF THE MODELS ACTUALLY SPREAD CLOUD COVERAGE A GOOD BIT THIS
AFTERNOON UNDER THE MID LEVEL CAP WHICH COULD RESTRICT READINGS
TO THE UPPER 80S IN SOME AREAS. WE MADE VERY FEW CHANGES TO THE
ONGOING FORECAST TRENDS OVERALL.

MOISTURE TENDS TO INCREASE SOMEWHAT OVERNIGHT ALONG COASTAL AREAS
AND WITH WEAK SPEED CONVERGENCE DEVELOPING AFTER MIDNIGHT...THERE
WILL PROBABLY BE A FEW SHOWERS DEVELOPING NEAR THE COAST AT SOME
POINT LATE...PERHAPS ALONG THE SAVANNAH RIVER ENTRANCE. WE HAVE
SMALL COASTAL RAIN CHANCES...BEST POTENTIAL SEEMS TO BE AT THE
BEACHES AND BARRIER ISLANDS. INLAND AREAS WILL BE DRY WITH SOME
LOW TEMPS AGAIN DIPPING INTO THE UPPER 60S.

&&

.SHORT TERM /THURSDAY THROUGH SATURDAY/...
THURSDAY AND THURSDAY NIGHT...THE DEEP AND BROAD TROUGH WILL REMAIN
ACROSS THE EASTERN CONUS AS THE OFFSHORE STATIONARY FRONT BEGINS TO
DRIFT BACK TOWARDS SHORE THURSDAY NIGHT. THURSDAY WILL BE A DAY
WHERE DEEP MOISTURE BEGINS TO INCREASE ACROSS THE AREA WITH PWATS
STARTING THE DAY AROUND 1.5 INCHES AND INCREASING TO AROUND 1.8
INCHES BY THE OVERNIGHT. LOW LEVEL FLOW WILL BE NORTHEAST TO
EASTERLY THROUGH THE DAY AND MODEL SOUNDINGS SHOW A CAPPED
ATMOSPHERE EVENTUALLY YIELDING WEAK INSTABILITY LATE IN THE DAY. WE
WILL LIKELY SEE A SLIGHT INCREASE IN SHOWER/THUNDERSTORM ACTIVITY
COMPARED TO WEDNESDAY AND SLIGHT CHANCE POPS SEEM REASONABLE. CLOUD
COVER WILL BE ON THE INCREASE AS WELL WHICH WILL KEEP TEMPERATURES
DOWN A BIT. LOOK FOR HIGHS IN THE UPPER 80S TO AROUND 90 WHICH IS A
COUPLE OF DEGREES BELOW NORMAL. OVERNIGHT...THE OFFSHORE STATIONARY
FRONT WILL WEAKEN AND BECOME AN OPEN TROUGH AS IT BEGINS TO MOVE
BACK CLOSER TO SHORE. RAIN CHANCES WILL BE CONFINED TO THE ADJACENT
COASTAL WATERS WHICH WILL BE CLOSER TO THE TROUGH AXIS AND ANY
CONVERGENCE WITHIN IT.

FRIDAY THROUGH SATURDAY...THE END OF THE WEEK AND START OF THE
WEEKEND WILL FEATURE INCREASING DEEP MOISTURE AND INCREASING RAIN
CHANCES ESPECIALLY BY SATURDAY. THE SURFACE TROUGH WILL BE ALIGNED
RIGHT ALONG THE SOUTHEAST COAST...COINCIDENT WITH THE SOUTHWEST FLOW
ALOFT ON THE EAST SIDE OF THE MID/UPPER LEVEL TROUGH AXIS. THERE
WILL EVEN BE A BIT OF INCREASING UPPER DIVERGENCE IN THE ENTRANCE
REGION OF A SUBTLE JET CENTERED WELL TO THE NORTHEAST. POPS FOR THIS
PERIOD HAVE BEEN HELD TO BE NO HIGHER THAN HIGH CHANCE. CONFIDENCE
IS INCREASING THAT LIKELY POPS...OR EVEN HIGHER WILL BE NEEDED AT
SOME POINT BUT THESE ROUNDS OF HIGHER RAIN CHANCES WILL BE TIED TO
SUBTLE EMBEDDED SHORTWAVE ENERGY THAT IS DIFFICULT TO PEG DOWN AT
THIS TIME. BY SATURDAY...PWATS SURGE TO AROUND 2.1 INCHES AND THE
POTENTIAL FOR LOCALLY HEAVY RAINFALL INCREASES. IN FACT...QPF PROGS
FROM WPC ARE QUITE WET FOR THIS PERIOD AND FEATURE THE POTENTIAL FOR
WIDESPREAD AMOUNTS IN EXCESS OF 1 INCH. WIDESPREAD CLOUD COVER AND
ROUND OF PRECIPITATION WILL KEEP HIGHS IN THE UPPER 80S WITH LOWS IN
THE LOW 70S.

&&

.LONG TERM /SATURDAY NIGHT THROUGH TUESDAY/...
THE UNSETTLED PATTERN WILL CONTINUE FOR THE LATTER HALF OF THE
WEEKEND AND AT LEAST INTO EARLY NEXT WEEK. THE TROUGH WILL REMAIN IN
THE VICINITY OF THE FORECAST AREA WITH A TROUGH ALOFT AND PWATS IN
EXCESS OF 2 INCHES. ALL THESE FACTORS ADD UP TO AN ACTIVE PERIOD
WITH RELATIVELY HIGH RAIN CHANCES. GIVEN THE TIME RANGE POPS HAVE
BEEN KEPT IN THE HIGH CHANCE RANGE...BUT IF THE MODELS CONTINUE
THEIR CURRENT TRENDS IT IS LIKELY THAT HIGHER POPS WILL EVENTUALLY
BE WARRANTED. LOCALLY HEAVY RAINFALL WILL REMAIN A CONCERN THROUGH
EARLY NEXT WEEK WITH ROUNDS OF CONVECTION ANTICIPATED. TEMPERATURES
WILL BE BELOW NORMAL...RUNNING ABOUT 3-5 DEGREES BELOW NORMAL FOR
HIGHS INTO THE MID WEEK TIME PERIOD.

&&

.AVIATION /08Z WEDNESDAY THROUGH SUNDAY/...
VFR THROUGH THE 00Z TAF PERIOD AT BOTH KCHS/KSAV. ISOLATED CONVECTION
MAINLY IN THE FORM OF SPOTTY SHOWERS POSSIBLE THIS AFTERNOON OR EARLY
EVENING BUT POTENTIAL FOR ANY ONE AREA GETTING RAIN IS QUITE LOW.

EXTENDED AVIATION...
A SURFACE TROUGH WILL DRIFT INTO THE AREA LATE THIS WEEK AND THROUGH
THE WEEKEND. AN ACTIVE PERIOD IS EXPECTED AND OCCASIONAL FLIGHT
RESTRICTIONS ARE POSSIBLE DURING THIS TIME.

&&

.MARINE...
WEAK MOISTURE AND PRES GRADIENTS PERSIST THROUGH TONIGHT BUT A WEAK
SURFACE LOW DEVELOPING OVER FLORIDA MAY ALLOW FOR A BIT MORE OF A
PRONOUNCED GRADIENT TONIGHT. FLOW MAINLY ONSHORE THE NEXT 24 HOURS
WITH SEAS 2 FT OR LESS TODAY INCREASING A BIT TO 2-3 FT TONIGHT.

THURSDAY THROUGH SUNDAY...THE OFFSHORE STATIONARY FRONT WILL
DISSIPATE INTO A SURFACE TROUGH AND DRIFT BACK TOWARD THE
SOUTHEAST COAST. AS THE TROUGH MOVES INTO THE COASTAL
WATERS...WINDS WILL VARY AT TIMES BUT WILL MAINLY BE EAST TO
SOUTHEASTERLY. THE GRADIENT MAY TIGHTEN UP AT TIMES AND SUPPORT
SOME MODESTLY STRONGER WINDS...BUT OVERALL WINDS WILL BE 15 KT OR
LESS WITH SEAS GENERALLY 2-4 FT. SMALL CRAFT ADVISORIES ARE NOT
ANTICIPATED AT THIS TIME.

&&

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

&&

$$

NEAR TERM...
SHORT TERM...BSH
LONG TERM...BSH
AVIATION...
MARINE...BSH






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