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Area Forecast Discussion

128
FXUS62 KCHS 242248
AFDCHS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
648 PM EDT THU APR 24 2014

.SYNOPSIS...
HIGH PRESSURE WILL REMAIN EAST OF THE AREA THROUGH FRIDAY AS A WEAK
COLD FRONT APPROACHES FROM THE WEST. THE FRONT WILL DROP THROUGH THE
AREA FRIDAY NIGHT WITH HIGH PRESSURE BUILDING IN THROUGH EARLY NEXT
WEEK. A STRONGER COLD FRONT WILL AFFECT THE REGION TOWARD THE MIDDLE
OF NEXT WEEK.

&&

.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
EARLY THURSDAY EVENING...ONGOING FORECASTS REMAINED IN GOOD SHAPE
AND REQUIRED ONLY MINOR ADJUSTMENTS TO HOURLY PARAMETERS.

TONIGHT...THE UPPER RIDGE AXIS WILL PUSH EAST OF THE AREA AS A
VIGOROUS MID/UPPER LEVEL SHORTWAVE CROSSES THE MID MISSISSIPPI
VALLEY AND INTO THE OHIO VALLEY. AS THIS OCCURS...A BROAD AREA OF
DIFLUENCE AHEAD OF THE TROUGH WILL SPREAD ACROSS THE EASTERN
SEABOARD. AT THE SURFACE...HIGH PRESSURE WILL REMAIN EAST OF THE
FORECAST AREA AS A FAST MOVING COLD FRONT APPROACHES FROM THE WEST.
AHEAD OF THE FRONT LATE TONIGHT...A WEAK PRE-FRONTAL TROUGH WILL LIFT
NORTHWARD WITH THE MODELS KICKING OFF ISOLATED SHOWERS AND POSSIBLY
A THUNDERSTORM OR TWO. THE GENERAL CONSENSUS AMONGST THE MODELS IS
THAT THE BEST CHANCE FOR SHOWERS/THUNDERSTORMS IS OVER THE COASTAL
WATERS AND THE FAR EASTERN ZONES INCLUDING EASTERN BERKELEY AND
CHARLESTON COUNTIES...MAINLY OVERNIGHT. WHILE THE LATEST NAM/HRRR
FORECASTS SUGGEST THAT LITTLE/NO PRECIPITATION WILL DEVELOP EVEN
OVERNIGHT...WE HAVE MAINTAINED SLIGHT CHANCE POPS IN THESE AREAS
OVERNIGHT. THE MODELS PROG A SURGE OF CAPE FROM THE SOUTH OVER THE
WATERS WHICH SHOULD BE SUFFICIENT TO JUSTIFY A MENTION OF THUNDER.
LOW LEVEL MOISTURE WILL INCREASE THROUGH THE NIGHT WITHIN THE
ONSHORE FLOW AND CLOUD COVER IS EXPECTED TO THICKEN. THE
COMBINATION OF INCREASED CLOUDINESS AND ENOUGH WIND TO PREVENT
BOUNDARY LAYER DECOUPLING WILL RESULT IN A MILD NIGHT. LOWS ARE
EXPECTED TO BE IN THE LOWER TO MID 60S ACROSS MUCH OF THE FORECAST
AREA.

&&

.SHORT TERM /6 AM FRIDAY MORNING THROUGH SUNDAY/...
A PROGRESSIVE MID-LEVEL SHORTWAVE WILL MOVE THROUGH NORTH CAROLINA
ON FRIDAY WITH VERY WEAK VORTICITY ENERGY TRAILING IT ACROSS SC.
FRIDAY MORNING WE MAY SEE ISOLATED SHOWERS OR TSTMS ACROSS OUR SC
WATERS AS A SURFACE TROUGH SHIFTS NORTHEAST UP THE COAST. BY MIDDAY
THERE MAY BE JUST ENOUGH SURFACE BASED INSTABILITY TO SUPPORT
ISOLATED SHOWERS AND TSTMS ACROSS MAINLY SOUTHERN SC AND THE
ADJACENT WATERS AS THE VORTICITY ENERGY MOVES IN AHEAD OF A WEAK
COLD FRONT. ANYTHING THAT DEVELOPS SHOULD DISSIPATE BY EARLY EVENING
WITH THE LOSS OF DAYTIME HEATING AND ONCE THE FLOW SWITCHES AROUND
TO WNW. PARTLY SUNNY SKIES AND A WARM ADVECTION REGIME MUCH OF THE
DAY WILL ALLOW HIGHS TEMPS TO RISE INTO THE MIDDLE 80S.

AN UPPER RIDGE WILL GRADUALLY BUILD OVER THE SOUTHEAST UNITED STATES
OVER THE WEEKEND WITH DRY WEATHER AND WARM TEMPS. INLAND AREAS WILL
RISE WELL INTO THE 80S BOTH DAYS WHILE COASTAL LOCATIONS REACH THE
MID TO UPPER 70S BEFORE BEING COOLED DOWN BY AN AFTERNOON SEA BREEZE.

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
LIGHT SOUTHERLY FLOW ALONG WITH MID LVL RIDGING OVER THE SOUTHEAST
WILL LIKELY KEEP WARMER TEMPS OVER THE SOUTHEAST INTO EARLY NEXT
WEEK AHEAD OF THE APPROACHING LOW PRESSURE SYSTEM. IN GENERAL...HIGH
TEMPS WILL BE IN THE LOW/MID 80S MONDAY AND TUESDAY BEFORE COOLING A
FEW DEGREES ON WEDNESDAY AS CLOUD COVER INCREASES WITH THE LOW
PRESSURE SYSTEM SHIFTING OVER THE EASTERN CONUS. A SLIGHT CHANCE OF
SHOWERS AND THUNDERSTORMS WILL REMAIN IN THE FORECAST ON MONDAY AS
SOUTHERLY FLOW DEEPENS MOISTURE OVER THE AREA WHILE AN H5 SHORTWAVE
PASSES OVERHEAD. PRECIP CHANCES SHOULD THEN INCREASE TUESDAY AND
WEDNESDAY AHEAD OF AN EASTWARD MOVING COLD FRONT ASSOCIATED WITH THE
LOW PRESSURE SYSTEM. THERE ARE INDICATIONS THAT WE COULD SEE AN
ENHANCED PERIOD OF SHOWERS AND/OR THUNDERSTORMS LATE TUESDAY INTO
WEDNESDAY AS STRONGER INSTABILITY AND WIND FIELDS SET UP OVER THE
SOUTHEAST AHEAD OF THE FRONT. A FEW THUNDERSTORMS COULD BE
STRONG...ESPECIALLY ON WEDNESDAY DURING PEAK HEATING. SHOWERS AND/OR
THUNDERSTORMS COULD PERSIST INTO MUCH OF THURSDAY AS THE COLD FRONT
SHIFTS OFFSHORE EARLY WHILE THE LARGE MID/UPPER LVL TROUGH REMAINS
POSITIONED OVER THE EASTERN CONUS. OVERALL TEMPS SHOULD COOL OFF
POST FROPA...WITH HIGHS ONLY IN THE MID/UPPER 70S ON THURSDAY.

&&

.AVIATION /00Z FRIDAY THROUGH TUESDAY/...
MVFR/IFR CEILINGS ARE POSSIBLE AS LOW LEVEL MOISTURE INCREASES
LATE TONIGHT/EARLY FRIDAY...ESPECIALLY AT KSAV. ALSO...A
SHOWER/THUNDERSTORM IS POSSIBLE LATE TONIGHT INTO FRIDAY...ESPECIALLY
AT KCHS. GIVEN MODEL SOUNDINGS AND CONSISTENT MOS GUIDANCE
TRENDS...INCLUDED A TEMPO GROUP FOR IFR CEILINGS AT KSAV 10-14Z.
OTHERWISE...CONFIDENCE IN FLIGHT RESTRICTIONS/PRECIPITATION
REMAINS TOO LOW TO WARRANT A MENTION WITHIN 00Z TAFS.

EXTENDED AVIATION OUTLOOK...VFR.

&&

.MARINE...
TONIGHT...HIGH PRESSURE WILL CONTINUE TO PERSIST EAST OF THE LOCAL
WATERS. AHEAD OF AN APPROACHING COLD FRONT FROM THE WEST...A WEAK
PRE-FRONTAL TROUGH WILL MOVE THROUGH WHICH MAY KICK OFF ISOLATED
SHOWERS AND THUNDERSTORMS. IT WILL ALSO BRING ABOUT A TURN IN THE
LOW LEVEL FLOW FROM MORE SOUTHEASTERLY TO MORE SOUTHERLY. WINDS WILL
GENERALLY BE 10-15 KT...PERHAPS UP TO 15-20 KT IN THE OUTER GEORGIA
WATERS NEAR 60 NM. SEAS WILL RANGE FROM 2-3 FT WITHIN 20 NM TO 3-4
FT BEYOND.

ON FRIDAY A MODEST SOUTHERLY FLOW WILL PREVAIL WITH AN AFTERNOON SEA
BREEZE ENHANCEMENT ALONG THE COAST. WINDS IN THE CHARLESTON HARBOR
COULD BLOW 15-20 KT IN THE AFTERNOON. WINDS AND SEAS WILL DROP OFF
CONSIDERABLY LATE FRIDAY NIGHT WITH THE PASSAGE OF A WEAK BACK DOOR
COLD FRONT FROM THE NORTH. AS HIGH PRESSURE EXPANDS ACROSS THE
WATERS OVER THE WEEKEND...WE EXPECT FAIRLY LIGHT WINDS THOUGH A WEAK
SEA BREEZE WILL DEVELOP EACH AFTERNOON.

WINDS/SEAS ARE EXPECTED TO REMAIN BELOW SMALL CRAFT ADVISORY LEVELS
THROUGH EARLY TUESDAY...BUT SHOULD APPROACH SMALL CRAFT ADVISORY
LEVELS BY TUESDAY NIGHT AS THE PRESSURE GRADIENT ENHANCES AHEAD OF A
COLD FRONT ADVANCING TO THE SOUTHEASTERN UNITED STATES BY MIDWEEK.
IN GENERAL...SOUTH/SOUTHEAST WINDS WILL REMAIN AT OR BELOW 15 KTS
THROUGH EARLY TUESDAY WHILE SEAS ARE NO HIGHER THAN 3-4 FT. BY
TUESDAY NIGHT...WINDS/SEAS SHOULD INCREASE/BUILD TO 20-25 KTS AND
4-6 FT...HIGHEST BEYOND 10 NM FROM THE COAST.

&&

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

&&

$$

SYNOPSIS...
NEAR TERM...BSH/SPR
SHORT TERM...JRL
LONG TERM...DPB
AVIATION...BSH/SPR
MARINE...BSH/JRL/SPR






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