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-- Discussion containing changed information from previous version are highlighted. --
000
FXUS62 KCHS 221318
AFDCHS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
918 AM EDT WED MAY 22 2013

.SYNOPSIS...
-- Changed Discussion --
ATLANTIC HIGH PRESSURE WILL PREVAIL THROUGH THURSDAY. A COLD
FRONT WILL MOVE ACROSS THE AREA THURSDAY NIGHT...WITH HIGH
PRESSURE BUILDING OVER THE REGION THROUGH EARLY NEXT WEEK.
-- End Changed Discussion --

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
-- Changed Discussion --
A WEAK UPPER TROUGH WILL PERSIST OVER THE REGION AGAIN
TODAY...WHILE ATLANTIC SURFACE HIGH PRESSURE EXTENDS INTO THE
SOUTHEAST STATES. DEEP LAYER MOISTURE REMAINS IN PLACE...WITH
PRECIPITABLE WATER VALUES AROUND 1.5 INCHES ACCORDING TO THE
UPPER AIR SOUNDINGS AT CHS AND JAX. DEEP LAYERED SOUTHERLY FLOW
WILL ALLOW THE SEABREEZE TO DEVELOP FAIRLY EARLY. WITH
TEMPERATURES PEAKING IN THE MID TO UPPER 80S...MODERATE
INSTABILITY WILL DEVELOP BY LATE MORNING/EARLY AFTERNOON. SHOWERS
AND THUNDERSTORMS WILL THUS INCREASE IN COVERAGE FROM LATE MORNING
INTO THE AFTERNOON...WITH THE ACTIVITY LIKELY SHIFTING GRADUALLY
INLAND FOLLOWING THE MOVEMENT OF THE SEABREEZE. CONVECTIVE
PARAMETERS ARE NOT IMPRESSIVE...HOWEVER AN ISOLATED SEVERE STORM
CANNOT BE RULED OUT WHERE BOUNDARY INTERACTIONS OCCUR.
-- End Changed Discussion --

&&

.SHORT TERM /6 PM THIS EVENING THROUGH SATURDAY/...
-- Changed Discussion --
DIURNAL CONVECTION WILL TAPER OFF EARLY THIS EVENING OVER
LAND...WHILE ISOLATED SHOWERS OR STORMS WILL REMAIN POSSIBLE OVER
THE COASTAL WATERS TONIGHT. SOME FOG IS POSSIBLE LATE
TONIGHT/EARLY THURSDAY MORNING...ESPECIALLY IN AREAS WHERE RAIN
OCCURS TODAY.

THURSDAY...ATLANTIC HIGH PRESSURE WILL PREVAIL WHILE WEAK TROUGHING
PERSISTS INLAND. A SHORTWAVE EMBEDDED WITHIN BROAD UPPER LEVEL
TROUGHING WILL CROSS THE REGION AND PUSH THE DEEP LAYERED MOISTURE
OFFSHORE AS THE DAY PROGRESSES. THERE IS THE POTENTIAL FOR ISOLATED
CONVECTION ACROSS THE AREA IN THE MORNING AHEAD OF THE SHORT
WAVE...WITH THE COVERAGE INCREASING TO SCATTERED IN THE AFTERNOON
ACROSS MUCH OF SOUTHEAST SOUTH CAROLINA WHERE PRECIPITABLE WATER
VALUES AND LOW LEVEL CONVERGENCE WILL BE MAXIMIZED. A
WESTERLY/DOWNSLOPE FLOW ALOFT WILL PUSH TEMPERATURES TO HIGHS IN THE
UPPER 80S TO AROUND 90 AWAY FROM THE IMMEDIATE COAST.

THURSDAY NIGHT...AN UPPER LEVEL TROUGH WILL DIG TOWARD THE
APPALACHIANS...PUSHING A COLD FRONT ACROSS THE AREA. OTHER THAN SOME
ISOLATED CONVECTION EARLY IN THE EVENING MAINLY ACROSS THE
CHARLESTON TRI-COUNTY AREA...THE FRONT SHOULD PASS THROUGH RELATIVE
RAIN-FREE DUE TO A LACK OF DEEP LAYERED MOISTURE. LOWS WILL BE IN
THE LOWER TO MID 60S.

FRIDAY...THE UPPER LEVEL TROUGH WILL MOVE OVER THE MID-ATLANTIC AS
SURFACE HIGH PRESSURE BEGINS TO BUILD IN FROM THE GREAT LAKES REGION
IN WAKE OF THE DEPARTING COLD FRONT. MUCH DRIER AIR WILL FILTER INTO
THE AREA WITH A STRONG NORTHWEST/DOWNSLOPE WIND COMPONENT. THERE
WILL BE CONSIDERABLE SUNSHINE ALONG WITH BREEZY CONDITIONS IN THE
AFTERNOON. THE DOWNSLOPE FLOW WILL NEGATE MUCH OF THE COLD AIR
ADVECTION...ALLOWING TEMPERATURES TO REACH HIGHS IN THE MID AND
UPPER 80S ACROSS THE AREA AWAY FROM THE IMMEDIATE COAST.

FRIDAY NIGHT...RADIATIONAL COOLING WILL BE LIMITED BY A COUPLED
NORTHERLY FLOW THROUGH MUCH OF THE NIGHT...BUT THE DRY AIR MASS AND
CLEAR SKIES SHOULD STILL ALLOW TEMPERATURES TO FALL INTO THE THE MID
AND UPPER 50S...WITH SOME LOWER 50S POSSIBLE WELL INLAND.

SATURDAY...AN EXTREMELY DRY AIR MASS WILL BE IN PLACE TO START THE
WEEKEND...WITH PRECIPITABLE WATER VALUES AS LOW AS .25 TO .50 INCHES
WHICH IS MORE THAN 2 STANDARD DEVIATIONS BELOW NORMAL FOR THIS TIME
OF YEAR. GIVEN THIS DRY AIR MASS...THERE WILL BE CONSIDERABLE
SUNSHINE BUT A NORTH-NORTHEAST FLOW WILL LIMIT HIGHS TO THE UPPER
70S TO LOWER 80S ACROSS SOUTHEAST SOUTH CAROLINA AND THE LOWER TO
MID 80S ACROSS SOUTHEAST GEORGIA.
-- End Changed Discussion --

&&

.LONG TERM /SATURDAY NIGHT THROUGH TUESDAY/...
MEDIUM RANGE GUIDANCE IS IN GOOD OVERALL AGREEMENT THROUGH THE LONG
TERM PERIOD. THE MID AND UPPER LEVEL PATTERN WILL FEATURE A NEARLY
ZONAL FLOW OVER THE REGION LATE IN THE WEEKEND INTO EARLY NEXT
WEEK...WITH A RIDGE THEN BUILDING TOWARD THE MIDDLE OF NEXT WEEK. AT
THE SURFACE...HIGH PRESSURE WILL PASS NORTH OF THE AREA LATE IN THE
WEEKEND...THEN SETTLE OVER THE WESTERN ATLANTIC THROUGH THE MIDDLE
OF NEXT WEEK.

RAIN-FREE CONDITIONS ARE EXPECTED TO PERSIST INTO EARLY NEXT
WEEK...THEN INCREASING MOISTURE COULD ALLOW FOR SOME MAINLY DIURNAL
ISOLATED CONVECTION ALONG AND AHEAD OF THE SEA BREEZE TUESDAY AND
WEDNESDAY. TEMPERATURES WILL BE SLIGHTLY BELOW NORMAL SUNDAY...THEN
RETURN TO NEAR OR SLIGHTLY ABOVE NORMAL NEXT WEEK.

&&

.AVIATION /13Z WEDNESDAY THROUGH SUNDAY/...
-- Changed Discussion --
ISOLATED CONVECTION IS EXPECTED TO DEVELOP IN THE VICINITY OF THE
TERMINALS LATE THIS MORNING ALONG THE SEA BREEZE...THEN SHIFT
INLAND OF THE TERMINALS LATER THIS AFTERNOON. COVERAGE/TIMING
UNCERTAINTIES PRECLUDE ANY MENTION IN THE TAFS OTHER THAN
VICINITY SHOWERS THROUGH MID-AFTERNOON AT KCHS AND LATE AFTERNOON
AT KSAV. ABUNDANT LOW LEVEL MOISTURE COULD RESULT IN SOME REDUCED
CEILINGS/VISIBILITIES LATE TONIGHT.

EXTENDED AVIATION...ATLANTIC HIGH PRESSURE WILL PREVAIL THROUGH
THURSDAY. A COLD FRONT WILL MOVE ACROSS THE AREA THURSDAY NIGHT
WITH HIGH PRESSURE THEN BUILDING OVER THE REGION THROUGH EARLY
NEXT WEEK.
-- End Changed Discussion --

&&

.MARINE...
-- Changed Discussion --
MARINE CONDITIONS LOOK PRETTY QUIET THROUGH TONIGHT AS THE AREA
REMAINS ON THE WESTERN PERIPHERY OF ATLANTIC HIGH PRESSURE. THE
SEABREEZE SHOULD DEVELOP LATE THIS MORNING...BUT WIND SPEEDS AT
THE COAST ARE STILL EXPECTED TO GENERALLY REMAIN BELOW 15 KT.

THURSDAY THROUGH MONDAY...ATLANTIC HIGH PRESSURE WILL DOMINATE
WITH SOUTHERLY FLOW UNTIL A COLD FRONT PUSHES OFFSHORE EARLY
FRIDAY. A NORTHERLY SURGE IS EXPECTED TO DEVELOP IN WAKE OF THE
FRONT FRIDAY NIGHT INTO EARLY SATURDAY AND COULD RESULT IN SMALL
CRAFT ADVISORY CONDITIONS. CONDITIONS WILL THEN IMPROVE LATER IN
THE WEEKEND INTO EARLY NEXT WEEK WITH WINDS/SEAS EXPECTED TO
REMAIN BELOW SMALL CRAFT ADVISORY THRESHOLDS.
-- End Changed Discussion --

&&

.TIDES/COASTAL FLOODING...
ATLANTIC HIGH PRESSURE WILL PREVAIL THROUGH THURSDAY. A COLD FRONT
WILL MOVE ACROSS THE AREA THURSDAY NIGHT WITH HIGH PRESSURE THEN
BUILDING OVER THE REGION THROUGH EARLY NEXT WEEK.

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
-- Changed Discussion --
GA...NONE.
SC...NONE.
MARINE...NONE.
-- End Changed Discussion --

&&

$$

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