Area Forecast Discussion
Issued by NWS Charleston, SC

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FXUS62 KCHS 060219
AFDCHS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
919 PM EST THU MAR 5 2015

.SYNOPSIS...
A COLD FRONT WILL PUSH OFF THE COAST TONIGHT THEN COLD HIGH PRESSURE
WILL BUILD OVER THE AREA THROUGH SUNDAY. NEXT WEEK...AN UNSETTLED
PATTERN WILL DEVELOP BETWEEN A STATIONARY FRONT SOUTH AND EAST OF
THE REGION AND HIGH PRESSURE CENTERED TO THE NORTH.

&&

.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
THURSDAY EVENING...ADJUSTED HOURLY FORECAST PARAMETERS...INCLUDING
POPS...WINDS AND TEMPS...BASED ON ONGOING/EXPECTED TRENDS.

THE INITIAL COLD FROPA FOLLOWED BY RAIN HAD PUSHED TEMPERATURES
INTO THE 50S/60S. A SECONDARY COLD FRONT MARKED BY AN ABRUPT WIND
SHIFT TO THE NORTH/NORTHEAST AND SHARPLY COLDER FEATURING
TEMPERATURES FALLING QUICKLY INTO THE 40S WAS ADVANCING INTO
NORTHERN COUNTIES OF THE FORECAST AREA...AND THIS MUCH COLDER
AIRMASS WILL DRIVE DEEPER INTO THE FORECAST AREA WITH TIME
TONIGHT. BY DAYBREAK...TEMPERATURES IN THE 30S/NEAR 40 WILL BE
COMMON NORTH OF INTERSTATE 16...AND TEMPERATURES NEAR THE SANTEE
RIVER COULD APPROACH FREEZING.

CATEGORICAL POPS SUPPORTED BY DEEP LAYERED FORCING FOR ASCENT AND
A PLUME OF PWATS AROUND 1.50 INCHES WILL GIVE WAY TO DRIZZLE/DECREASING
COVERAGE OF MEASURABLE RAIN DURING THE NEXT FEW HOURS. BY LATE
TONIGHT...THERE IS A LOW PROBABILITY THAT LIGHT DRIZZLE COULD
BEGIN TO FREEZE ON SOME ELEVATED SURFACES SUCH AS TREES AND METAL
OBJECTS ACROSS INLAND BERKELEY COUNTY. HOWEVER...THE PROBABILITY
FOR FREEZING PRECIPITATION/ASSOCIATED IMPACTS REMAINS TOO LOW TO
WARRANT A FREEZING RAIN ADVISORY.

LAKE WINDS...WINDS WILL SHIFT TO THE NORTH AND WILL INCREASE
BEHIND A STRONG COLD FRONT THIS EVENING AND OVERNIGHT. SPEEDS WILL
INCREASE TO THE 20-25 KT RANGE...AND GUSTS AS HIGH AS 30 KT WILL
BE POSSIBLE. A LAKE WIND ADVISORY REMAINS IN EFFECT.

&&

.SHORT TERM /6 AM FRIDAY MORNING THROUGH SUNDAY/...
THE COLD FRONT WILL GRADUALLY SHIFT OFFSHORE FRIDAY MORNING THOUGH
LOW LEVEL MOISTURE AND WEAK ISENTROPIC ASCENT WILL LINGER INTO MID
TO LATE MORNING. THIS COULD SPUR SOME LIGHT DRIZZLE THROUGH THE
MORNING HOURS UNTIL DRIER AIR SHIFTS IN DURING THE AFTERNOON.
MODERATE COLD ADVECTION AND PERSISTENT CLOUD COVER WILL RESULT IN
HIGH TEMPS IN THE MID TO UPPER 40S.

THE SURFACE HIGH WILL SETTLE OVER THE AREA FRIDAY NIGHT WITH MOSTLY
CLEAR SKIES AND LIGHT WINDS. THIS WILL FACILITATE STRONG RADIATIONAL
COOLING AND TEMPERATURES DROPPING BELOW FREEZING IN MANY AREAS. THE
EXCEPTION LOOKS TO BE THE GA COASTAL ZONES AND IMMEDIATE SC COAST.
WE ISSUED A FREEZE WATCH FOR ALL ZONES MINUS THE GA COASTAL AREAS
FOR FRIDAY NIGHT.

DRY TEMPS AND A WARMING TREND ARE EXPECTED SATURDAY INTO SUNDAY AS
THE SURFACE HIGH SHIFTS OFFSHORE AND A SOUTHERLY LOW-LEVEL FLOW
DEVELOPS. MOSTLY SUNNY SKIES EXPECTED SATURDAY BEFORE HIGH CIRRUS
INCREASES ON SUNDAY. HIGHS WILL BE IN THE LOWER 60S SATURDAY AND
UPPER 60S TO NEAR 70 ON SUNDAY.

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
BETWEEN A STATIONARY FRONT OFF THE SOUTHEAST COAST AND ACROSS THE FL
PENINSULA AND HIGH PRESSURE CENTERED NORTH OF THE REGION...A
BAROCLINIC ZONE WILL WAVER OVER THE REGION AND WILL CONTRIBUTE TO
UNSETTLED CONDITIONS NEXT WEEK. WHILE A MOSTLY CLOUDY REGIME
PUNCTUATED BY PERIODS OF PRECIPITATION AND FINALLY DEVOID OF ANY
COLD AIR APPEARS LIKELY...CONFIDENCE REGARDING COMPLEX FORECAST
DETAILS REMAINS LOW. FOR INSTANCE...WE MAINTAIN CHANCE POPS MONDAY
AND TUESDAY...BUT SOME GUIDANCE SUGGESTS THAT LIKELY/CATEGORICAL
POPS WILL EVENTUALLY BE NEEDED FOR THIS PERIOD. ALSO...THE POTENTIAL
FOR THUNDERSTORMS COULD INCREASE...BUT THE UNCERTAIN DETAILS
REGARDING INDIVIDUAL WAVES OF LOW PRESSURE AND AN ASSOCIATED
UNCERTAIN POTENTIAL FOR AN INFLUX OF ANY SIGNIFICANT INSTABILITY
DOES NOT JUSTIFY ANY MENTION OF THUNDER.

&&

.AVIATION /02Z FRIDAY THROUGH TUESDAY/...
MVFR AND PERIODS OF IFR CONDITIONS ARE EXPECTED OVERNIGHT.
THE PROSPECTS FOR IMPROVEMENT REMAIN LIMITED FRIDAY AS LOW LEVEL
MOISTURE PERSISTS BENEATH A STRENGTHENING SUBSIDENCE INVERSION.
THUS...MAINTAINED MVFR CEILINGS AT KCHS THROUGH FRIDAY...BUT
INDICATED A RETURN OF VFR CONDITIONS AT KSAV AFTER 18Z FRIDAY.

EXTENDED AVIATION OUTLOOK...VFR LIKELY FRIDAY NIGHT THROUGH THIS
WEEKEND. FLIGHT RESTRICTIONS POSSIBLE IN RAIN EARLY NEXT WEEK.

&&

.MARINE...
THURSDAY EVENING...UPDATED FORECASTS AND ISSUED A MARINE WEATHER
STATEMENT TO ADDRESS PERSISTENT/PATCHY SEA FOG REPORTED OVER
NEARSHORE WATERS. THIS FOG WILL DISSIPATE QUICKLY AS A STRONG COLD
FRONT PASSES OVER THE NEXT FEW HOURS.

TONIGHT...A WIND SHIFT TO THE NORTHWEST AND A BRIEF PERIOD OF
SUB-SCA WINDS WILL GIVE WAY TO RAPID DETERIORATION AS A SECONDARY
COLD FRONT USHERS AN ABRUPT WIND SHIFT TO THE NORTH/NORTHEAST
AND QUICKLY INCREASING WINDS AS COLD ADVECTION AND A TIGHTENING
PRESSURE GRADIENT SPREAD ACROSS THE WATERS. THE ONGOING GALE
WARNING FOR THE CHARLESTON COUNTY WATERS AND THE OUTER GEORGIA
WATERS STILL LOOKS ON TRACK AND REMAINS IN EFFECT.
ELSEWHERE...INCLUDING CHARLESTON HARBOR...SMALL CRAFT ADVISORY
CONDITIONS WILL DEVELOP LATER THIS EVENING AND WILL CONTINUE
THROUGH THE OVERNIGHT.

GALES WILL TRANSITION TO SMALL CRAFT ADVISORIES ON FRIDAY AS THE
GRADIENT RELAXES AND HIGH PRESSURE CONTINUES TO BUILD IN FROM THE
NW. ELEVATED N/NE WINDS AND ASSOCIATED SEAS WILL PERSIST INTO
SATURDAY. A MORE TRANQUIL REGIME IS EXPECTED AS HIGH PRESSURE SHIFTS
OVER THE WATERS SATURDAY NIGHT THROUGH SUNDAY. THEN...FORECAST
CONFIDENCE DECREASES NEXT WEEK AS WINDS/SEAS WILL DEPEND ON A HIGHLY
UNCERTAIN STORM TRACK. THE LATEST FORECAST HOLDS WINDS/SEAS WELL
BELOW ADVISORY LEVELS...BUT AN OFFSHORE TRACK FOLLOWED BY DEEPER
AREAS OF LOW PRESSURE WILL TRANSLATE TO STRONGER WINDS AND HIGHER
SEAS.

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...FREEZE WATCH FROM FRIDAY EVENING THROUGH SATURDAY MORNING FOR
     GAZ087-088-099>101-114>116-118-137-138-140.
SC...FREEZE WATCH FROM FRIDAY EVENING THROUGH SATURDAY MORNING FOR
     SCZ040-042>045-047>052.
     LAKE WIND ADVISORY UNTIL 2 PM EST FRIDAY FOR SCZ045.
MARINE...SMALL CRAFT ADVISORY UNTIL 4 PM EST FRIDAY FOR AMZ352-354.
     GALE WARNING UNTIL 11 AM EST FRIDAY FOR AMZ350.
     GALE WARNING UNTIL 2 PM EST FRIDAY FOR AMZ374.
     SMALL CRAFT ADVISORY UNTIL 11 AM EST FRIDAY FOR AMZ330.

&&

$$
SYNOPSIS...
NEAR TERM...SPR
SHORT TERM...JRL
LONG TERM...SPR
AVIATION...JRL/SPR
MARINE...JRL/SPR



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