Area Forecast Discussion
Issued by NWS Charleston, SC

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000
FXUS62 KCHS 191808
AFDCHS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
208 PM EDT FRI SEP 19 2014

.SYNOPSIS...
HIGH PRESSURE WILL BUILD TO THE NORTH OF THE REGION TODAY AS A WEAK
AREA OF LOW PRESSURE DEVELOPS OFF THE SOUTHEAST COAST AND LIFTS
NORTHEASTWARD THROUGH THE WEEKEND. A COLD FRONT WILL STALL JUST
SOUTH OF THE AREA MONDAY THROUGH WEDNESDAY WITH HIGH PRESSURE
BUILDING FROM THE NORTH. A TROUGH OF LOW PRESSURE MAY DEVELOP OFF
THE SOUTHEAST COAST MID TO LATE NEXT WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
EARLY THIS AFTERNOON...BY AND LARGE THE DEVELOPMENT OF CONVECTION
HAS GONE AS EXPECTED THUS FAR. THE TWO MAIN AREAS ARE SOUTH OF
I-16 IN SOUTHEAST GEORGIA AND THE TRI-COUNTY AREA. SO FAR...A FEW
OF THE STRONGER STORMS HAVE CAUSED DECENT WIND GUST OBSERVATIONS
INCLUDING A 38 KNOT GUST AT KSVN. SO...ANY STRONGER STORMS WILL BE
CAPABLE OF PRODUCING GUSTY WINDS. WE CAN/T TOTALLY DISCOUNT THE
POSSIBILITY OF A SEVERE THUNDERSTORM BUT THE OVERALL PROBABILITY
IS QUITE LOW DUE TO THE SOMEWHAT LIMITED INSTABILITY. LOCALLY
HEAVY RAINFALL IS STILL A CONCERN BUT THESE SHOWERS AND STORMS
APPEAR TO BE MOVING FOR EXCESSIVE RAIN TO NOT BE MUCH OF A
CONCERN.

TONIGHT...LOW LEVEL MOISTURE CONVERGENCE SHOULD SHIFT BACK TO THE
IMMEDIATE COAST AND BEACHES AND THERE COULD BE SOME SUSTAINED
DOWNPOURS ALONG THE BEACHES AND BARRIER ISLANDS IF ANY CONVECTION
ANCHORS TO ANY ONE SPOT FOR LONG. PLENTY OF CLOUDS WITH LOWS
IN THE UPPER 60S MANY AREAS.

&&

.SHORT TERM /SATURDAY THROUGH MONDAY/...
THE UPPER LOW WILL SHIFT OFF THE SOUTHEAST COAST ON SATURDAY...
PULLING THE SURFACE LOW AWAY FROM THE AREA. MEANWHILE COOL HIGH
PRESSURE WILL BRIEFLY BUILD DOWN THE EASTERN SEABOARD. EXTENSIVE
PRECIPITATION ASSOCIATED WITH THE COASTAL LOW WILL BE ONGOING DURING
THE MORNING...SHIFTING SLOWLY ENE AS THE DAY WEARS ON WITH DRIER AIR
FILTERING IN FROM THE NORTHWEST. WRAP AROUND MOISTURE WILL MAINTAIN
EXTENSIVE STRATUS THROUGH EARLY TO MID AFTERNOON. THIS COMBINED WITH
WEAK COLD ADVECTION WILL YIELD HIGH TEMPS IN THE LOWER 80S.

ON SUNDAY A ZONAL FLOW WILL DEVELOP WITH WEAK SOUTHERLY BOUNDARY
LAYER WINDS. DOWNSLOPE FLOW WILL ALLOW DRIER AIR TO MIX DOWN WITH
DEWPOINTS DROPPING INTO THE LOWER 60S BY AFTERNOON. MOSTLY SUNNY
SKIES EXPECTED WITH ANY RESIDUAL PRECIPITATION CONFINED TO THE
COASTAL WATERS AND MAINLY DURING THE MORNING. ADIABATIC WARMING
ALONG WITH STRONG INSOLATION WILL PRODUCE HIGH TEMPS IN THE MIDDLE
80S.

A SHORTWAVE DROPPING INTO THE AREA FROM THE OHIO VALLEY WILL PUSH A
WEAK COLD FRONT INTO THE SOUTHEAST UNITED STATES MONDAY AFTERNOON.
THE UPPER LEVEL ENERGY WILL BECOME ORPHANED FROM THE MEAN LAYER FLOW
AND LINGER OVER THE SOUTHEAST COAST FOR A FEW DAYS. THE COLD FRONT
WILL INITIALLY LACK MUCH MOISTURE CONVERGENCE BUT THIS WILL INCREASE
AS IT SINKS SLOWLY SOUTH. WE ARE ONLY CARRYING A SLIGHT CHANCE POP
FOR MONDAY AFTERNOON DUE TO THE FRONT. PRE-FRONTAL COMPRESSION WILL
YIELD HIGH TEMPS IN THE MID TO UPPER 80S.

&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
COOL AND DRY HIGH PRESSURE WILL BUILD DOWN THE EASTERN SEABOARD AT
THE SURFACE WHILE A COASTAL TROUGH LINGERS JUST OFFSHORE. THERE WILL
PROBABLY BE A SHARP PRECIP GRADIENT FOR MUCH OF THE PERIOD WITH
INLAND AREAS DRY AND CONSIDERABLE SHOWER AND TSTM COVERAGE OVER THE
WATERS AND IMMEDIATE COASTAL AREAS. THERE ARE INDICATIONS THE
COASTAL TROUGH WILL STRENGTHEN WEDNESDAY OR THURSDAY AND SHIFT
INLAND WHICH WOULD INCREASE SKY COVER AND RAIN POTENTIAL FARTHER TO
THE WEST. TEMPS WILL GENERALLY BE AT OR SLIGHTLY BELOW NORMAL DURING
THE PERIOD.

&&

.AVIATION /18Z FRIDAY THROUGH WEDNESDAY/...
CONDITIONS LOOK QUITE UNSETTLED AT BOTH KCHS AND KSAV THROUGH 18Z
SATURDAY. THIS AFTERNOON...SHOWERS AND ISOLATED THUNDERSTORMS MAY
IMPACT THE TERMINALS THROUGH ABOUT 21Z. BASED ON CURRENT
RADAR...KCHS APPEARS TO HAVE THE BEST CHANCE. NO TEMPO HAS BEEN
INCLUDED FOR NOW AND WE WILL AMEND AS NEEDED. IF EITHER SITE WERE
TO BE DIRECTLY IMPACTED...GUSTY WINDS AND BRIEF REDUCTIONS IN
VISIBILITY ARE THE MAIN CONCERNS.

TONIGHT...AN AREA OF LOW PRESSURE WILL BEGIN TO DEVELOP WELL TO
THE SOUTH AND A BAND OF CONVERGENCE ALONG THE COAST WILL LEAD TO
THE REDEVELOPMENT OF SHOWERS AND ISOLATED THUNDERSTORMS. BOTH
SITES ONCE AGAIN WILL SEE AT LEAST VCSH WITH THE POTENTIAL FOR
DIRECT IMPACTS THROUGH THE OVERNIGHT PERIOD. THERE ARE ALSO
INDICATIONS THAT CEILINGS COULD DEVELOP. I HAVE KEPT THE FORECAST
VFR WITH CEILINGS AT 3500 FT. PRECIPITATION CONCERNS WANE TOWARDS
THE END OF THE FORECAST PERIOD THOUGH BREEZY CONDITIONS ARE
EXPECTED WITHIN THE TIGHT NORTHEAST PRESSURE GRADIENT ACROSS THE
REGION.

EXTENDED AVIATION OUTLOOK...PRIMARILY VFR.

&&

.MARINE...
HIGH PRESSURE POSITIONING TO THE NORTH OF THE MARINE AREA AND LOWER
PRESSURE OFF THE FLORIDA COAST WILL RESULT IN STRENGTHENING
EAST/NORTHEAST FLOW THROUGH TONIGHT. MODELS IN GOOD AGREEMENT ON
SOME SOLID PINCHING OF THE GRADIENT ALONG THE SOUTH CAROLINA
COAST TONIGHT AND WE HAVE ISSUED A SMALL CRAFT ADVISORY FOR THE
CHARLESTON COASTAL WATERS TONIGHT AND PERSISTING INTO SATURDAY
MORNING. WE WILL NEED TO WATCH TRENDS IN THE CHARLESTON HARBOR AS
WINDS PEAK CLOSER TO 20 KT LATER TODAY AND THIS EVENING. THE
COMBINATION OF WIND AND SWELL WAVE WILL STILL MAKE FOR A ROUGH
PASSAGE THROUGH THE JETTIES. THE NE SURGE WILL BE WEAKER FURTHER
SOUTH TONIGHT BUT ENOUGH TO PEAK INTO THE 15-20 KT RANGE AT TIMES
WITH SEAS BUILDING TO 3 TO 4 FT.

A NORTHEAST GRADIENT WILL CONTINUE SATURDAY INTO SUNDAY WITH
MARGINAL SMALL CRAFT ADVISORY CONDITIONS POSSIBLE OVER THE
CHARLESTON NEARSHORE AND GA OFFSHORE WATERS. A BRIEF SOUTHERLY FLOW
EXPECTED SUNDAY NIGHT INTO MONDAY BEFORE A COLD FRONT DROPS THROUGH
THE WATERS AND HIGH PRESSURE BUILDS FROM THE NORTH. A PROLONGED
NORTHEAST SURGE EXPECTED TUESDAY THROUGH FRIDAY WITH SMALL CRAFT
ADVISORIES INCREASINGLY LIKELY WEDNESDAY AND THEREAFTER.

RIP CURRENTS...LINGERING BACK SWELL FROM TC EDOUARD WILL STILL
IMPACT THE BEACHES TODAY...AND THAT ALONG WITH STRONGER NE AND
EAST WINDS WILL SUPPORT A MODERATE RISK OF RIP CURRENTS AT AREA
BEACHES. AN ELEVATED RISK MAY PERSIST INTO THE WEEKEND AS THE
GRADIENT REMAINS RATHER PINCHED WITH ENHANCED NE AND EAST WINDS
TO CONTINUE.

&&

.TIDES/COASTAL FLOODING...
WITH A PROLONGED NNE FLOW EXPECTED...AND ASTRONOMICAL TIDE
PREDICTIONS AT CHARLESTON OF 5.8 TO 5.9 FT MLLW...IT IS LOOKING LIKE
WE WILL BE DEALING WITH SHALLOW COASTAL FLOODING FOR A NUMBER OF
HIGH TIDE CYCLES. THE LATE AFTERNOON INTO EARLY EVENING HIGH TIDE IS
WHEN THE FLOODING WOULD OCCUR. MODERATE CHANCES OF SEEING ENOUGH OF
A WIND-INDUCED ANOMALY TO REACH 7.0 FT MLLW TODAY THROUGH SUNDAY
WITH MODERATE-HIGH CHANCES TUESDAY THROUGH FRIDAY AS WINDS INCREASE.
WILL INCLUDE MENTION IN THE HAZARDOUS WEATHER OUTLOOK.

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
SC...NONE.
MARINE...SMALL CRAFT ADVISORY FROM 8 PM THIS EVENING TO 11 AM EDT
     SATURDAY FOR AMZ350.

&&

$$

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




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