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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS62 KCHS 190127
AFDCHS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
927 PM EDT TUE JUN 18 2013

.SYNOPSIS...
A COLD FRONT WILL APPROACH FROM THE NORTHWEST TONIGHT...THEN
SLOWLY PROGRESS THROUGH THE AREA WEDNESDAY AND THURSDAY. HIGH
PRESSURE WILL THEN BUILD FROM THE NORTH INTO THE WEEKEND AND
SETTLE OVER THE ATLANTIC EARLY NEXT WEEK.

&&

.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
-- Changed Discussion --
AN EXPANSIVE UPPER LEVEL TROUGH WILL REMAIN IN PLACE OVER THE
EASTERN STATES TONIGHT. MEANWHILE AT THE SURFACE...A COLD FRONT
EXTENDS FROM LOW PRESSURE ALONG THE MID-ATLANTIC COAST SOUTHWEST
THROUGH THE PIEDMONT OF NORTH CAROLINA...THE UPSTATE OF SOUTH
CAROLINA AND INTO NORTHERN GEORGIA LATE THIS EVENING. AS THE LOW
SHIFTS OFF THE MID-ATLANTIC COAST LATER TONIGHT...THE FRONT WILL
SLOWLY DROP TOWARD THE AREA BUT BECOME MORE WEST-EAST ORIENTED AND
SLOW AS IT BECOMES NEARLY PARALLEL TO THE FLOW ALOFT.

WEAKENING UPSTREAM CONVECTION OUT AHEAD OF THE COLD FRONT WILL
CONTINUE TO PROGRESS TOWARD THE AREA LATE THIS EVENING...AND
EXPECT SOME OF IT TO HOLD TOGETHER AS IT SHIFTS INTO THE AREA
AFTER ABOUT 11 PM WITH SUPPORT OF A MID-LEVEL IMPULSE APPROACHING
FROM THE WEST. WILL THEREFORE KEEP A SLIGHT CHANCE OR CHANCE OF
SHOWERS AND THUNDERSTORMS IN THE FORECAST TONIGHT. WHILE A STRONG
OR SEVERE THUNDERSTORM IS POSSIBLE...THE ATMOSPHERE SHOULD
STABILIZE SOME WITH THE LOSS OF DIURNAL HEATING.

THE TEMPERATURE CURVE WILL SHOW SLOWLY FALLING TEMPERATURES...BEFORE
LATE NIGHT HEAT LOSS IS MAXIMIZED AND LOWS REACH THE LOWER AND
MIDDLE 70S.
-- End Changed Discussion --

&&

.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH FRIDAY/...
WEDNESDAY AND THURSDAY...A COLD FRONT WILL SLOWLY SHIFT OVER
SOUTHEAST SOUTH CAROLINA AND SOUTHEAST GEORGIA BY WEDNESDAY MORNING
BEFORE GRADUALLY STALLING SOUTH OF THE REGION BY THURSDAY. AS THIS
OCCURS...PWATS NEAR 2.0 INCHES ALONG WITH MID LVL FORCING FROM AN H5
SHORTWAVE SHOULD FAVOR PERIODS OF SHOWERS/THUNDERSTORMS THROUGH MUCH
OF WEDNESDAY...ESPECIALLY ALONG/NEAR THE PASSING COLD FRONT. HAVE
THEREFORE INCREASED POPS TO 50-60 WEDNESDAY AFTERNOON MAINLY ALONG
COASTAL LOCATIONS IN SOUTHEAST GEORGIA CLOSER TO THE FRONT. AT THIS
TIME...CLOUD COVER WILL REMAIN A LIMITING FACTOR FOR STRONGER
THUNDERSTORMS TO DEVELOP OVER THE REGION. HOWEVER...WEAK WIND FIELDS
WILL LIKELY RESULT IN SLOW STORM MOTIONS THAT MAY CONTRIBUTE TO
HEAVY RAINFALL DURING A FEW THUNDERSTORMS.

A GRADUAL DECREASE IN OVERALL POPS SHOULD THEN OCCUR FROM NORTH TO
SOUTH WEDNESDAY NIGHT INTO THURSDAY AS THE FRONT SLOWLY SLIPS TO THE
SOUTH OF THE FORECAST AREA...BUT HAVE MAINTAINED A MENTION OF PRECIP
OVER ALL LOCATIONS THROUGH THURSDAY NIGHT...WITH 20 POPS OVER INLAND
SOUTH CAROLINA TO 30-40 POPS OVER LOCATIONS SOUTH OF INTERSTATE 16
IN GEORGIA. OVERALL HIGH TEMPS ARE EXPECTED TO PEAK IN THE MID/UPPER
80S OVER MOST LOCATIONS WEDNESDAY AND THURSDAY...WITH SLIGHTLY COOLER
TEMPS IN THE MID 80S OVER SOUTH CAROLINA BEHIND THE FRONT. OVERNIGHT
LOWS ARE EXPECTED TO BE IN THE UPPER 60S TO LOWER 70S.

FRIDAY...SURFACE HIGH PRESSURE WILL BUILD INTO THE REGION FROM THE
NORTH...WITH THE PATTERN EVENTUALLY TRANSITIONING INTO AN INLAND
WEDGE/COASTAL TROUGH TYPE SCENARIO. A FEW MODELS INDICATE A WEAK
WAVE/SFC LOW DEVELOPING ALONG THE STALLED FRONT JUST OFFSHORE LATE
MORNING/EARLY AFTERNOON BEFORE DRIFTING ONSHORE DURING THE EVENING.
A SLIGHT CHANCE TO CHANCE OF SHOWERS AND/OR THUNDERSTORMS WILL
THEREFORE BE MAINTAINED IN THE CURRENT FORECAST...WITH HIGHEST
CHANCES OVER SOUTHEAST GEORGIA COUNTIES. OVERALL HIGH TEMPS SHOULD
REMAIN IN THE MID/UPPER 80S WITH SLIGHTLY COOLER TEMPS ALONG COASTAL
COUNTIES AND THE TRI COUNTY AREA DUE TO ENHANCED CLOUD COVER AND
HIGH PRESSURE NUDGING IN FROM THE NORTH.

&&

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
A WEAK INLAND WEDGE/COASTAL TROUGH PATTERN WILL PERSIST INTO
SATURDAY...BEFORE THE TROUGH DAMPENS BY SUNDAY AS HIGH PRESSURE
SETTLES OVER THE ATLANTIC. THE FORECAST AREA WILL THEN REMAIN
ALONG THE WESTERN PERIPHERY OF THE ATLANTIC HIGH PRESSURE INTO
EARLY NEXT WEEK. SHOWER/THUNDERSTORM CHANCES WILL RANGE FROM
AROUND 20 TO 30 PERCENT EACH AFTERNOON AND EARLY EVENING...BEFORE
DIMINISHING OVERNIGHT AS MORE TYPICAL FOR EARLY SUMMER. THE
INITIALLY WEAK AND ILL DEFINED UPPER LEVEL PATTERN WILL TRANSITION
INTO BROAD RIDGING ALOFT...SUPPORTING A GRADUAL WARMING TREND
THROUGH THE PERIOD. HIGH TEMPERATURES AROUND 90 DEGREES AWAY FROM
THE COASTLINE SATURDAY AND SUNDAY WILL WARM INTO THE LOWER 90S BY
MONDAY AND TUESDAY.

&&

.AVIATION /02Z WEDNESDAY THROUGH SUNDAY/...
VFR CONDITIONS ARE GENERALLY EXPECTED TO PREVAIL THROUGH 00Z
THURSDAY. TIMING UPSTREAM CONVECTION...THUNDERSTORMS HAVE BEEN ADDED TO THE
FORECAST IN A TEMPO GROUP FROM 03-06Z AT KCHS AND 04-07Z AT KSAV.
THERE COULD BE SOME MVFR CEILINGS WEDNESDAY MORNING...BUT THERE IS
NOT ENOUGH CONFIDENCE TO INCLUDE MENTION IN THE FORECAST AT THIS
TIME. THE PROXIMITY OF A FRONT WILL RESULT IN SCATTERED TO
NUMEROUS SHOWERS AND THUNDERSTORMS FROM MIDDAY WEDNESDAY THROUGH
THE EARLY EVENING AND HAVE VICINITY THUNDERSTORMS IN THE FORECAST
AT BOTH TERMINALS STARTING AT 16Z.

EXTENDED AVIATION...MVFR CIGS/VSBYS POSSIBLE THROUGH THURSDAY DUE
TO SHOWERS AND/OR THUNDERSTORMS. LOW CHANCE OF MVFR CIGS/VSBYS
FRIDAY AFTERNOON/EVENING WITH A COASTAL TROUGH/SFC LOW SHIFTING
ONSHORE.

&&

.MARINE...
TONIGHT...THE PRESSURE GRADIENT IS CONTINUING TO TIGHTEN BETWEEN
THE STRONG SUB-TROPICAL ATLANTIC RIDGE TO THE SE AND AN UPSTREAM
COLD FRONT TO THE NW. THE PACKING OF THE ISOBARS WILL BECOME
GREATEST EARLY TONIGHT BETWEEN THE COLD FRONT AND ATLANTIC
HIGH...AS GEOSTROPHIC WINDS CLIMB TO 25-30 KT. THIS IS SUPPORTIVE
OF A MARGINAL SCA ACROSS OUR OUTER GA WATERS FOR SOME 5-6 FOOTERS
AND FREQUENT GUSTS OF 25 KT. THE OTHER WATERS LOOK TO REMAIN JUST
BELOW ANY HEADLINE CONDITIONS...WITH WINDS PEAKING AT 15 OR 20 KT
AND SEAS AT 3-5 FT.

WEDNESDAY THROUGH SATURDAY...WINDS/SEAS ARE EXPECTED TO REMAIN BELOW
SMALL CRAFT ADVISORY CRITERIA AS A COLD FRONT SHIFTS OVER THE
COASTAL WATERS WEDNESDAY BEFORE STALLING NEAR/OVER SOUTHERN GA
WATERS ON THURSDAY. AS THE FRONT SLOWLY SHIFTS SOUTH...SOUTHERLY
WINDS WILL VEER BEHIND THE FRONT AND EVENTUALLY BECOME
NORTHEAST/EAST THURSDAY. HIGH PRESSURE WILL THEN BUILD FROM THE
NORTH OVER THE WATERS INTO EARLY FRIDAY...WITH WIND SPEEDS
APPROACHING 15-20 KTS OVER NORTHERN SC WATERS AND SEAS BUILDING TO
3-4 FT. ENHANCED EAST/NORTHEAST FLOW MAY CONTINUE INTO SATURDAY
AS A COASTAL TROUGH DEVELOPS OFFSHORE AND GRADUALLY SHIFTS OVER LAND.

RIP CURRENTS...WE HAVE MAINTAINED A MODERATE RISK AT THE BEACHES
THROUGH THIS EVENING...DUE TO SOUTH AND SW WINDS AT 15 TO 20 MPH
AND A 2 FOOT SWELL EVERY 10 SECONDS. THE RISK FOR TOMORROW HOWEVER
IS LOW WITH MUCH LESS WIND.

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
SC...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 5 AM EDT WEDNESDAY FOR AMZ374.

&&

$$

SYNOPSIS...
NEAR TERM...JAQ
SHORT TERM...DPB
LONG TERM...
AVIATION...JAQ
MARINE...JAQ/DPB