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240
FXUS62 KCHS 170822
AFDCHS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
422 AM EDT WED SEP 17 2014

.SYNOPSIS...
A COLD FRONT WILL MOVE SOUTHWARD ACROSS THE REGION THROUGH TONIGHT.
AN INLAND WEDGE OF HIGH PRESSURE WILL THEN PREVAIL IN THE WAKE OF
THE FRONT INTO THE WEEKEND. ANOTHER COLD FRONT WILL APPROACH FROM
THE WEST EARLY NEXT WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
PRE-DAWN...AREAS OF LAYERED CLOUDS ACROSS THE FORECAST AREA THIS
MORNING WITH AREAS OF STRATUS CLOUDS AND FOG DEVELOPING ACROSS
INLAND SOUTH CAROLINA WHERE WIDESPREAD RAINS RE-SATURATED THE
SOILS AGAIN ON TUESDAY. THE LOW CLOUDS COULD CERTAINLY EXPAND EAST
AND SOUTH BY DAYBREAK WITH AREAS OF FOG EXPECTED. AT THIS POINT...
WIDESPREAD DENSE FOG PROBLEMS DO NOT LOOK TOO LIKELY GIVEN LATEST
BUFR FORECAST SOUNDINGS WITH HIGH MOISTURE PROFILES UP TO 850 MB.
A FEW INLAND AREAS COULD SEE VSBYS 1/2 MILE OR LESS AT TIMES.
ISOLATED SHOWERS ARE POSSIBLE JUST ABOUT ANYWHERE NORTH OF
BEAUFORT NEARING DAWN...BUT THE BULK OF THE CONVECTION WILL
PROBABLY REMAIN EITHER CLOSER TO THE BEACHES...JUST OFFSHORE OR
MOSTLY N OF THE AREA.

WEAK CYCLOGENESIS WILL OCCUR OFF THE GEORGIA AND SOUTH CAROLINA
COASTS THIS MORNING AS INCREASING CYCLONIC FLOW ALOFT SPREADS OVER
THE SOUTHEAST STATES TODAY. DEEPER MOISTURE AND ENHANCED UPPER
FORCING WILL ALSO BE ASSOCIATED WITH THE EXITING LOW PRES OFF THE
COAST. IN THE LOW LEVELS A FAIRLY DISORGANIZED BACKDOOR SURFACE
COLD FRONT IS FORECAST TO SLIDE THROUGH THE FORECAST AREA TODAY
IN THE WAKE OF THE ATLC LOW PRES MOVING OUT.

IT LOOKS LIKE MAINLY ISOLATED CONVECTION FOR THE MORNING HOURS
WITH A ROUND OF SCATTERED SHOWERS AND STORMS FOR THIS AFTERNOON
AND EVENING AS A SERIES OF MID LEVEL SHORT WAVE TROUGHS RIPPLE
E AND SE THROUGH GEORGIA AND SOUTH CAROLINA. COVERAGE/DURATION
SHOULD BE LESS OVER SOUTH CAROLINA TODAY BUT WE WILL HAVE TO
WATCH FOR A REGION OF UPPER DIFLUENCE PROGGED BY JUST ABOUT ALL
THE MODELS LATE DAY. UPPER FORCING COULD ENHANCE THE CONVECTIVE
POTENTIAL DURING THE LATE AFTERNOON HOURS ACROSS PARTS OF E
CENTRAL OR NE SOUTH CAROLINA. WE RAISED POPS INTO THE 40 PERCENT
RANGE NE OF WALTERBORO TO ACCOUNT FOR THIS POTENTIAL. OTHERWISE...
TYPICAL LATE SUMMER THERMODYNAMICS ANTICIPATED WITH JUST ENOUGH
MID/UPPER FLOW TO SUGGEST SOME MULTI-CELL ORGANIZATION AT TIMES.
WE CANNOT RULE OUT ISOLATED STRONG TSTMS EITHER BUT CONFIDENCE
WITH THE MESOSCALE IS QUITE LOW WITH THE WEAKLY SLOPED FRONTAL
ZONE IN THE AREA. SOME OF THE TSTMS WILL ALSO PRODUCE DOWNPOURS
WHICH WILL WILL BE SLOW TO RUN OFF AROUND HIGH TIDE IF STORMS CROP
UP ALONG THE COAST TOWARD MID AFTERNOON. DEEP LAYERED STEERING IS
ALSO GENERALLY TOWARD THE COAST AS WELL.

TONIGHT...LATER SHIFTS CAN TAKE A HARDER LOOK AT LATE NIGHT FOG
POTENTIAL BUT CHANCES SEEM TO BE THERE NEARING DAWN ON THU.
POPS SHIFT OFFSHORE LATER IN THE EVENING WITH PARTLY CLOUDY
SKIES MOST AREA.

&&

.SHORT TERM /THURSDAY THROUGH SATURDAY/...
THURSDAY...THE COLD FRONT WILL STEADILY PROGRESS OFFSHORE AND
EVENTUALLY PULL NORTH/NORTHEAST...AS A WAVE OF LOW PRESSURE
DEVELOPS ALONG THE FEATURE AND LIFTS AHEAD OF SHORTWAVE ENERGY IN
THE BASE OF THE UPPER TROUGH. HIGH PRESSURE OVER THE GREAT LAKES
REGION WILL SLOWLY BUILD TOWARD THE MID ATLANTIC STATES AND
CAROLINAS BEHIND THE DEPARTING FRONT...INTRODUCING A NOTABLY DRIER
AIR MASS INTO THE FORECAST AREA. ANY ISOLATED SHOWER ACTIVITY ON
THURSDAY WILL LIKELY BE CONFINED TO THE CHARLESTON TRI COUNTY
REGION AND SC/GA COASTAL COUNTIES...WHERE SEABREEZE AND COASTAL
CONVERGENCE COULD PROVIDE SOME FORCING FOR WEAK CONVECTION. HIGH
TEMPERATURES WILL REFLECT A COOLING TREND...PEAKING IN THE LOW TO
MID 80S UNDER PARTLY CLOUDY SKIES. LOW TEMPERATURES WILL ALSO BE
NOTABLY COOLER...FALLING INTO THE MID TO UPPER 60S OVERNIGHT. BEST
RAIN CHANCES DURING THE NIGHTTIME PERIOD WILL BE FOUND OVER THE
MARINE ZONES...HOWEVER AN ISOLATED SHOWER COULD MOVE INTO THE
COASTLINE WITHIN ONSHORE FLOW.

FRIDAY AND SATURDAY...AS THE CENTER OF HIGH PRESSURE TO THE NORTH
MOVES OVER THE NEW ENGLAND STATES FRIDAY AND SHIFTS OFF THE
NORTHERN COASTLINE SATURDAY...AN INLAND WEDGE WILL AMPLIFY DOWN
THE MID ATLANTIC AND SOUTHEAST STATES. THE UPPER TROUGH WILL
GRADUALLY DIMINISH LATE WEEK INTO THE WEEKEND...WHILE A WEAK
UPPER LOW TAKES SHAPE JUST OFF THE SOUTHEAST COAST. EXPECT THE
ENERGY WITHIN THIS FEATURE TO SUPPORT THE DEVELOPMENT OF A WELL-
DEFINED COASTAL TROUGH AT THE SURFACE. BEST RAIN POTENTIAL WILL
MAINLY BE FOUND ALONG THE COAST AND OVER THE MARINE
ZONES...CLOSEST TO MOISTURE AND CONVERGENCE WITHIN THE COASTAL
TROUGH. HAVE THUS INDICATED A DISTINCT WEST-EAST GRADIENT IN RAIN
CHANCES FRIDAY AND SATURDAY...WITH SLIGHT CHANCES LESS THAN 25
PERCENT ACROSS INLAND ZONES THAT INCREASE TO SOLID CHANCES IN THE
30 TO 40 PERCENT RANGE FOR COASTAL COUNTIES...HIGHEST DURING THE
AFTERNOON PERIODS. COOL NORTHEAST FLOW WITHIN THE INLAND WEDGE OF
HIGH PRESSURE WILL SUPPRESS TEMPERATURES BELOW SEASONAL
NORMALS...RISING ONLY INTO THE LOWER 80S EACH DAY. LOW
TEMPERATURES FRIDAY NIGHT WILL TREND EVEN COOLER THAN THE PREVIOUS
DAY...RANGING FROM THE LOW TO MID 60S AWAY FROM THE LOCALLY WARMER
COASTLINE.

&&

.LONG TERM /SATURDAY NIGHT THROUGH TUESDAY/...
A COASTAL TROUGH ON THE PERIPHERY OF INLAND HIGH PRESSURE WILL
LIFT NORTH/NORTHEAST ACROSS THE ATLANTIC WATERS SUNDAY...WHILE
THE INLAND WEDGE EVENTUALLY ERODES AHEAD OF A STRONG COLD FRONT
UPSTREAM. PRECIPITATION POTENTIAL ON SUNDAY WILL BE SIMILAR TO
PREVIOUS DAYS...MAINLY FOCUSED ACROSS THE COASTAL COUNTIES WITH
RAIN-FREE CONDITIONS FARTHER INLAND. THE COLD FRONT WILL CONTINUE
TO APPROACH FROM THE NORTHWEST ON MONDAY...AS A PRE-FRONTAL SURFACE
TROUGH SHIFTS OVER THE EAST COAST STATES. THE COLD FRONT THEN
STEADILY MOVES THROUGH THE FORECAST AREA EARLY TUESDAY...FOLLOWED
BY EXPANSIVE HIGH PRESSURE WITH ORIGINS FROM THE NORTHERN PLAINS.
MEDIUM RANGE MODEL SOLUTIONS ARE NOT INDICATING SIGNIFICANT
PRECIPITATION ASSOCIATED WITH THE FRONTAL PASSAGE...AND HAVE THUS
CAPPED RAIN CHANCES GENERALLY BELOW 30 PERCENT FOR THE EARLY WEEK
PERIOD. TEMPERATURES COULD REBOUND AHEAD OF THE FRONT ON MONDAY AND
PEAK IN THE MID TO UPPER 80S...BEFORE A NOTABLE COOLING TREND
OCCURS IN THE WAKE OF THE FRONT TUESDAY AND WEDNESDAY.

&&

.AVIATION /08Z WEDNESDAY THROUGH SUNDAY/...
LOW STRATUS WAS DEVELOPING PRIOR TO 08Z W AND N OF KCHS AND WE
EXPECT IFR CONDITIONS TO SET IN LATER TONIGHT AS THESE LOW CLOUDS
EXPAND. THERE COULD ALSO BE FOG WITH VSBYS BELOW 1 NM BUT AT THIS
TIME CONFIDENCE IS BETTER ON LOW CIGS. AT KSAV,,,WE TRENDED A BIT
MORE OPTIMISTIC LATER TONIGHT WITH MVFR VSBYS AND SCATTERED LOW
CLOUDS IN THE FIRST COUPLE HUNDRED FEET. IF COULD BECOME IFR OR
LOWER BUT FORECAST SOUNDINGS ARE FAR FROM CONCLUSIVE.

LOW CIGS AND ANY FOG AROUND AT DAYBREAK SHOULD GIVEN WAY TO VFR
CONDITIONS BY LATE MORNING INTO THE AFTERNOON HOURS. THERE ARE
ADDITIONAL CHANCES FOR SCATTERED SHOWERS AND TSTMS AGAIN THIS
AFTERNOON...WE HAVE VCSH AFTER MIDDAY TO TREND.

EXTENDED AVIATION OUTLOOK...OUTSIDE OF SHRA AND/OR TSRA...FLIGHT
RESTRICTIONS WILL BE POSSIBLE EACH MORNING WITH FOG AND/OR LOW
STRATUS SHIFTING ONSHORE.

&&

.MARINE...
GROUND SWELL FROM DISTANT MAJOR HURRICANE EDOUARD TRICKLING INTO OUR
COASTAL WATERS EARLY THIS MORNING...AND ADDITIONAL SWELL ENERGY IS
TO ARRIVE AS TIME PROGRESSES. SEAS 2 FT NEAR SHORE WILL BUILD TO
3 TO 4 FT WELL OFFSHORE TODAY INTO TONIGHT. AS A COLD FRONT MOVES
THROUGH THIS MORNING LIGHT AND VARIABLE WINDS SHOULD BECOME MORE
ONSHORE BUT SPEEDS MAINLY 10 KT OR LESS THROUGH TONIGHT. THE
SUBTLE LONG PERIOD SWELL COULD MAKE FOR LOCALLY ROUGH CONDITIONS
AROUND THE JETTIES...ESPECIALLY AROUND TIMES OF LOW TIDE.

THURSDAY THROUGH SUNDAY...LIGHT NORTHEAST WINDS BEHIND THE COLD
FRONT ON THURSDAY WILL BEGIN TO SURGE BY FRIDAY...AS A WEDGE OF
HIGH PRESSURE STRENGTHENS INLAND AND A COASTAL TROUGH AMPLIFIES
TO THE SOUTHEAST. WINDS WILL INCREASE TO 15 TO 20 KT ACROSS
PORTIONS OF THE MARINE ZONES FRIDAY AND SATURDAY...WHILE SEAS
BUILD TO 3 TO 5 FT. LATEST NUMERICAL MODEL SOLUTIONS SUGGEST
CONDITIONS WILL REMAIN JUST BELOW SMALL CRAFT ADVISORY CRITERIA
AT THIS TIME. CONDITIONS SHOULD MODERATE OVER THE WATERS AS THE
INLAND WEDGE WEAKENS BY SUNDAY.

RIP CURRENTS...LONG PERIOD SWELL FROM HURRICANE EDOUARD WILL OCCUR
ALONG THE BEACHES TODAY INTO THURSDAY. DESPITE ONLY LIGHT
ONSHORE WINDS...1-2 FT SWELLS WITH PERIODS NEAR 14 SECONDS SUPPORT
AN ENHANCED PERIOD OF RIP CURRENTS ALONG THE SOUTH CAROLINA AND
GEORGIA BEACHES. A MODERATE RISK OF RIP CURRENTS TODAY...AND
POSSIBLY THURSDAY.

&&

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

&&

$$

NEAR TERM...
SHORT TERM...WMS
LONG TERM...WMS
AVIATION...
MARINE...WMS







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