Area Forecast Discussion
Issued by NWS Charleston, SC

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000
FXUS62 KCHS 161506
AFDCHS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
1106 AM EDT WED APR 16 2014

.SYNOPSIS...
HIGH PRESSURE WILL BUILD NORTH OF THE REGION THROUGH THURSDAY NIGHT.
AN AREA OF LOW PRESSURE MAY AFFECT THE REGION FRIDAY AND SATURDAY
AS IT PASSES BY TO THE EAST OVER THE ATLANTIC. HIGH PRESSURE WILL
THEN RETURN TO THE AREA EARLY NEXT WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
TODAY...NO MAJOR CHANGES TO THE PREVIOUS FORECAST. HIGH PRESSURE
WILL REMAIN TO THE NORTH WITH AN UNSEASONABLY COOL AIR MASS
PERSISTING OVER THE REGION. LOW-LEVEL MOISTURE RIDING SOUTHWEST
AROUND THE EASTERN EDGE OF THE HIGH WILL FLIRT WITH THE
COAST...LIKELY PUSHING A BIT MORE ONSHORE ACROSS SOUTHEAST GEORGIA
WHERE THE TRAJECTORIES ARE MORE EASTERLY. THE TIGHT PRESSURE
GRADIENT WILL SUPPORT BREEZY CONDITIONS THROUGH THE
DAY...STRONGEST AT THE COAST...WHILE THE DIMINISHING LOW-LEVEL JET
WILL MAKE FOR A LESSENING OF THE WIND GUSTS. HIGH TEMPS SHOULD
ONLY REACH THE LOWER 60S ACROSS SOUTHERN SC/INTERIOR SOUTHEAST GA
WITH MID 60S ELSEWHERE. COASTAL LOCALES WILL REMAIN
CHILLIER...LIKELY ONLY TOPPING OUT AROUND 60.

LAKE WINDS...A TIGHT PRESSURE GRADIENT AND DECENT MIXING ACROSS LAKE
MOULTRIE WILL SUPPORT A LAKE WIND ADVISORY INTO THE FIRST PART OF
THIS AFTERNOON.

TONIGHT...WILL HAVE TO WATCH FOR ANY SIGNIFICANT DECOUPLING POTENTIAL
WELL INLAND TO THE NORTH OF I-16 AS LOW TEMPS DIP TOWARD THE MID
30S AT SOME OF THE NORMALLY COLDER RURAL LOCATIONS FROM ALLENDALE
TO SUMMERVILLE. WE CONTINUE TO SHOW JUST ENOUGH GRADIENT/WIND TO
OMIT ANY MENTIONS FOR PATCHY FROST ESPECIALLY SINCE THE GRADIENT
TIGHTENS BEFORE DAWN ON THURSDAY AND THERE IS A WEAK MOIST FLUX
COMING IN FROM THE ATLC IN THE BOUNDARY LAYER. MORE OF AN ONSHORE
COMPONENT ACROSS SE GEORGIA SHOULD KEEP READINGS A BIT WARMER
ALONG AND S OF I-16 OVERNIGHT. SOME INCREASE IN STRATOCU COASTAL
AREAS IS LIKELY LATE WITH WEAK ISENTROPIC LIFT DEVELOPING.

&&

.SHORT TERM /THURSDAY THROUGH SATURDAY/...
THURSDAY AND THURSDAY NIGHT...ALOFT THE REGION WILL BE IN THE
SOUTHWEST FLOW ASSOCIATED WITH THE BROAD LONGWAVE THAT ENCOMPASSES
MUCH OF THE EASTERN HALF OF THE CONUS. THE STRONG DAMMING 1043 MB
HIGH OVER THE NORTHEAST WILL PERSIST THOUGH IT WILL BEGIN TO RETREAT
EVEN FURTHER NORTHEASTWARD WITH TIME. THIS WILL LEAVE THE AREA IN
THE STRONG RIDGING EAST OF THE APPALACHIANS WITH COOL NORTHEAST FLOW
PREVAILING. MODEL TIME HEIGHTS AND SOUNDINGS SHOW ALL OF THE
MOISTURE IN THE COLUMN CONFINED TO THE LOWEST 5 KFT WITH
CONSIDERABLE DRY AIR IN THE MID AND UPPER LEVELS. THE MODELS
CONTINUE TO SHOW POTENTIAL FOR SHOWER DEVELOPMENT OVER THE COASTAL
WATERS AND PERHAPS ALONG THE GEORGIA COAST ON THURSDAY. BY THURSDAY
NIGHT RAIN CHANCES BEGIN TO EXPAND NORTHWARD AND FURTHER INLAND AS
AN AREA OF LOW PRESSURE BEGINS TO ORGANIZE OVER THE NORTHEAST GULF.
THURSDAY POPS HAVE BEEN LIMITED TO SLIGHT CHANCES AND THURSDAY NIGHT
HAVE BEEN CAPPED AT CHANCE FOR NOW. HIGHS WILL BE ON THE COOL SIDE
WITH UPPER 60S IN MOST LOCATIONS. LOWS WILL BE IN THE UPPER 40S
INLAND AND NORTH...WITH MID TO UPPER 50S FURTHER SOUTH.

FRIDAY THROUGH SATURDAY...THE FORECAST BECOMES MORE INTERESTING AND
INHERENTLY LESS CERTAIN FOR THE LATE WEEK AND EARLY WEEKEND. IN
GENERAL...THE MODELS SHOW A SOUTHERN STREAM DISTURBANCE IN THE
MID/UPPER LEVELS SWINGING THROUGH THE NORTHERN GULF AND KICKING OFF
SURFACE LOW DEVELOPMENT. AS THIS LOW DEVELOPS...MOISTURE WILL SPREAD
NORTHWARD ALONG AND JUST OFF THE SOUTHEAST COAST WITH THE POTENTIAL
FOR INCREASING RAINFALL CHANCES. SPECIFIC MODEL SOLUTIONS TRULY RUN
THE SPECTRUM. FOR INSTANCE THE 00Z/16 ECMWF ALLOWS THE UPPER
DISTURBANCE TO DEEPEN SIGNIFICANTLY AND FORM A CLOSED LOW OVER THE
FLORIDA PANHANDLE FRIDAY NIGHT. THIS RESULTS IN A SLOWER DEVELOPING
LOW WITH TREMENDOUS MOISTURE AND DEEP FORCING TO SPREAD INTO
SOUTHEAST GEORGIA AND SOUTHEAST SOUTH CAROLINA. SUCH A SOLUTION
WOULD RESULT IN THE POTENTIAL FOR WIDESPREAD HEAVY RAINFALL THROUGH
THE DAY ON SATURDAY. ON THE OTHER HAND...THE GFS IS MUCH WEAKER WITH
THE UPPER DISTURBANCE AND RESULTING LOW AND KEEPS THE PRECIP AXIS
LIGHTER AND OVER NORTH FLORIDA AND THE ATLANTIC. GIVEN THE
UNCERTAINTY AND EXISTING MODEL DISAGREEMENT...I HAVE NOT MADE ANY
SIGNIFICANT CHANGES TO THE FORECAST. POPS FEATURE A TIGHT GRADIENT
WITH HIGHEST VALUES OVER THE WATERS. I HAVE INTRODUCED SOME
CATEGORICAL POPS OVER THE WATERS AND TO THE SOUTH...BUT MAINTAINED
THE SLIGHT CHANCE TO CHANCE POPS FOR INLAND AREAS. OBVIOUSLY ALL OF
THE FORECAST PARAMETERS WILL ULTIMATELY BE DETERMINED BY THE
DEVELOPMENT AND TRACK OF THE LOW BUT FOR NOW TEMPS FEATURE ANOTHER
COOL DAY ON FRIDAY FOLLOWED BY NEAR NORMAL VALUES FOR SATURDAY.

&&

.LONG TERM /SATURDAY NIGHT THROUGH TUESDAY/...
EARLY IN THE PERIOD THERE IS STILL CONSIDERABLE UNCERTAINTY
REGARDING THE SURFACE LOW OFF THE FLORIDA COAST. THE DEEPER MODEL
SOLUTIONS KEEP THE LOW LINGERING AROUND WITH RAIN STILL ONGOING
ALONG THE SOUTHEAST COAST. BY MONDAY OR MONDAY NIGHT...THE LOW IS
EXPECTED TO PULL AWAY AND HIGH PRESSURE WILL RETURN TO THE REGION. A
COLD FRONT MAY ATTEMPT TO SAG IN FROM THE NORTH LATE IN THE PERIOD
WITH SOME MODEST INCREASE IN RAIN CHANCES. OVERALL...TEMPERATURES
ARE EXPECTED TO BE RIGHT AROUND CLIMO...ESPECIALLY BY THE MIDDLE OF
NEXT WEEK.

&&

.AVIATION /15Z WEDNESDAY THROUGH SUNDAY/...
VFR CONDITIONS AT BOTH KSAV AND KCHS THROUGH 06Z THURSDAY. THE
MAIN ISSUE TODAY WITH BE N TO NE SURFACE WINDS PRODUCING PREVAILING
GUSTS IN THE 20-25 KT RANGE THROUGH MID-LATE AFTERNOON.

EXTENDED AVIATION OUTLOOK... LOW CHANCES FOR PERIODIC SUB-VFR
CONDITIONS BEGINNING FRIDAY AS MARINE STRATOCUMULUS ATTEMPT TO
MOVE ONSHORE. BETTER CHANCES FOR FLIGHT RESTRICTIONS WILL OCCUR BY
SATURDAY AS LOW PRESSURE MOVES OUT OF THE GULF OF MEXICO AND OFF
THE EAST COAST OF FLORIDA.

&&

.MARINE...
THROUGH TONIGHT....HIGH PRES WEDGING INTO GEORGIA AND THE
CAROLINAS FROM THE NORTH WILL MAINTAIN TIGHT THERMAL AND MOISTURE
GRADIENTS OVER THE ATLC WATERS FROM CHARLESTON TO SOUTH OF
SAVANNAH. WINDS WILL BE NE WITH THE MORNING SURGE EBBING AND THEN
RAMPING UP AGAIN AFTER MIDNIGHT TONIGHT. SMALL CRAFT ADVISORIES
WILL CONTINUE ALL WATERS AND THE CHARLESTON HARBOR THROUGH TONIGHT
WITH SEAS BUILDING TO 5 TO 7 FT NEAR SHORE AND REMAINING 7-9 FT
CLOSER TO THE GULF STREAM.

THURSDAY THROUGH SUNDAY...A STRONG RIDGE OF HIGH PRESSURE WILL
REMAIN ACROSS INLAND AREAS WITH A TIGHT NORTHEAST GRADIENT IN PLACE
ACROSS THE LOCAL WATERS. THE GRADIENT WILL HELP SUPPORT SOLID SMALL
CRAFT ADVISORY WINDS/SEAS THROUGH THE REST OF THE WEEK AND INTO THE
UPCOMING WEEKEND. FORECAST CONFIDENCE THEN LESSENS EARLY IN THE
WEEKEND AS AN AREA OF LOW PRESSURE IS EXPECTED TO CROSS THE FLORIDA
PENINSULA AND EMERGE OVER THE ATLANTIC. THE EVENTUAL TRACK OF THIS
LOW AND THE RESULTING GRADIENT ON ITS NORTH SIDE WILL DETERMINE
MARINE CONDITIONS THROUGH THE END OF THE FORECAST PERIOD. WINDS AND
SEAS COULD INCREASE IF THE LOW MOVES CLOSER TO THE AREA DURING THIS
TIME...BUT THERE IS NOT ENOUGH CONFIDENCE IN THE FORECAST TO SAY AT
THIS POINT.

RIP CURRENTS...MODERATE RISK FOR RIP CURRENTS ALL BEACHES TODAY AS
THE LOW-LEVEL FLOW TIPS NORTHEAST AND COMBINE WITH ELEVATED SEAS
AND LINGERING ASTRONOMICAL INFLUENCES. STRONG NORTHEAST WINDS AND
LINGERING ASTRONOMICAL INFLUENCES WILL RESULT IN AN ENHANCED RISK
OF RIP CURRENTS THROUGH AT LEAST FRIDAY.

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
SC...LAKE WIND ADVISORY UNTIL 2 PM EDT THIS AFTERNOON FOR SCZ045.
MARINE...SMALL CRAFT ADVISORY UNTIL NOON EDT SATURDAY FOR AMZ350-352-
     354.
     SMALL CRAFT ADVISORY UNTIL 8 AM EDT SUNDAY FOR AMZ374.
     SMALL CRAFT ADVISORY UNTIL 5 PM EDT THURSDAY FOR AMZ330.

&&

$$

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






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