Area Forecast Discussion
Issued by NWS Charleston, SC

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FXUS62 KCHS 292244
AFDCHS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
644 PM EDT FRI MAY 29 2015

.SYNOPSIS...
A WEAK TROUGH OF LOW PRESSURE WILL DEVELOP OFFSHORE TONIGHT AND
WILL MOVE INLAND SATURDAY. HIGH PRESSURE WILL THEN RETURN SUNDAY AND
WILL PERSIST UNTIL A BACKDOOR COLD FRONT AFFECTS THE AREA MID WEEK.

&&

.NEAR TERM /UNTIL 6 AM SATURDAY MORNING/...
THIS EVENING...DIURNAL SHOWERS IN HAMPTON AND ALLENDALE COUNTIES
WILL QUICKLY FADE BY SUNSET. OTHER SHOWERS ARRIVING FROM OFF THE
ATLANTIC ALONG COASTAL SE GA WILL ALSO GRADUALLY DISSIPATE.
ELSEWHERE WE LOOK FOR RAIN FREE WEATHER WITH TEMPS MAINLY IN THE
70S.

TONIGHT...A COASTAL TROUGH WILL FORM OUT NEAR THE WESTERN WALL OF
THE GULF STREAM AND THEN SHIFTS CLOSER TO SHORE LATE. THE BEST
MOISTURE CONVERGENCE WITH THIS FEATURE WILL STAY OVER THE OCEAN
THE FIRST HALF OF THE NIGHT...BUT EVENTUALLY BETTER CONVERGENCE
WILL OCCUR CLOSER TO THE SHORE AND THEN ONSHORE THE COASTAL
ZONES OVERNIGHT. COVERAGE SHOULD GENERALLY BE ISOLATED OR
SCATTERED...AND ONCE RADAR TRENDS BECOME BETTER DEFINED WE CAN
ADJUST COVERAGE AS NECESSARY. POOR LAPSE RATES AND DRY AIR ABOVE
700 MB WILL NEGATE THE NEED FOR ANY MENTION OF THUNDER OVER LAND.

TEMPS WILL BE NOWHERE NEAR AS COOL INLAND AS THEY WERE LAST NIGHT
GIVEN WARM ADVECTION AND HIGHER DEW POINTS. LOWS WILL RANGE FROM
MID AND UPPER 60S INLAND FROM THE INTRA-COASTAL TO THE LOWER 70S
ON THE BARRIER ISLANDS DUE TO THE PROXIMITY TO THE WARMING OCEAN
WATERS.

&&

.SHORT TERM /6 AM SATURDAY MORNING THROUGH MONDAY/...
SATURDAY...A WEAK TROUGH OF LOW PRESSURE LOCATED OFFSHORE AT
DAYBREAK WILL MOVE INLAND THROUGH THE DAY. CONVERGENCE ALONG THE
TROUGH WILL ALLOW SHOWERS AND ISOLATED THUNDERSTORMS TO
DEVELOP...THUS HAVE CHANCE POPS GENERALLY SHIFTING FROM THE COASTAL
LOCATIONS TO INTERIOR COUNTIES AS THE TROUGH MOVES ONSHORE. OVERALL
SEVERE THREAT LOOKS PRETTY LOW GIVEN WEAK SHEAR...UNIMPRESSIVE LAPSE
RATES...AND MARGINAL CAPE. WENT WITH PERSISTENCE FORECAST ON
TEMPERATURES WITH HIGHS IN THE MID TO UPPER 80S AWAY FROM THE
LOCALLY COOLER COAST WHERE HIGHS WILL ONLY BE IN THE LOW 80S.
ACTIVITY WILL DIMINISH IN THE EVENING AS HIGH PRESSURE REDEVELOPS.
SATURDAY NIGHT IS EXPECTED TO BE DRY...WITH LOWS RANGING FROM THE
MID 60S TO AROUND 70.

SUNDAY INTO MONDAY...SURFACE HIGH PRESSURE WILL PREVAIL.
ALOFT...UPPER RIDGE OFF THE SOUTHEAST COAST WILL BEGIN TO BUILD
WHILE BROAD LONGWAVE TROUGH REMAINS OVER THE GREAT LAKES REGION.
SHOWERS AND THUNDERSTORMS WILL BE POSSIBLE ALONG THE SEA BREEZE EACH
AFTERNOON...WITH HIGHEST CHANCES EXPECTED TO BE INLAND. ANY
CONVECTION THAT DEVELOPS WILL DIE OFF NEAR SUNSET WITH LOSS OF
HEATING. HIGHS WILL MAINLY BE IN THE UPPER 80S TO NEAR 90 AWAY FROM
THE BEACHES. LOWS IN THE UPPER 60S/LOW 70S.

&&

.LONG TERM /MONDAY NIGHT THROUGH FRIDAY/...
LOOKS A BIT MORE UNSETTLED THIS PERIOD AS A BACKDOOR COLD FRONT
APPROACHES FROM THE NORTH AND SETTLES NEAR OR OVER THE AREA MID WEEK
AND DEEPER MOISTURE MOVES IN FROM THE SOUTH AND EAST AHEAD OF A
CUTOFF LOW OVER THE U.S. GULF COAST REGION. BOTH THE 12Z/29 GFS AND
ECMWF ARE SHOWING LOW PRESSURE OFF THE SOUTHEAST U.S. COAST AT THE
END OF THE PERIOD SO WILL HAVE TO KEEP AN EYE ON THIS POTENTIAL
LATER NEXT WEEK. EITHER WAY THIS PATTERN MEANS HIGHER THAN NORMAL
RAIN CHANCES AND COOLER THAN NORMAL HIGH TEMPS.

&&

.AVIATION /23Z SATURDAY THROUGH WEDNESDAY/...
ODDS FAVOR VFR CONDITIONS THROUGH THE 18Z TAF PERIOD.
HOWEVER...MODEL SOUNDINGS SUGGEST THAT MVFR/IFR CEILINGS COULD
DEVELOP FOR A TIME LATE TONIGHT INTO EARLY SATURDAY. WILL CONTINUE
TO ASSESS.

EXTENDED AVIATION OUTLOOK...MAINLY VFR. SMALL CHANCE FOR FLIGHT
RESTRICTIONS WITHIN SHRA/TSRA OVER THE WEEKEND INTO EARLY NEXT WEEK.

&&

.MARINE...
TONIGHT...EASTERLY WINDS HAVE BEEN TEMPORARILY DISRUPTED A BIT
ACROSS PARTS OF THE GA WATERS DUE TO SHOWERS. OTHERWISE...A
SPRAWLING RIDGE OF ATLANTIC HIGH PRESSURE ACROSS THE WATERS WILL
GIVE WAY TO AN INVERTED TROUGH THAT FORMS ACROSS THE MARINE
COMMUNITY AROUND 03-06Z AS IT ATTEMPTS TO HEAD WESTWARD. THIS
KEEPS A FAIRLY DECENT GRADIENT GOING THROUGH THE NIGHT...CAUSING
EAST AND NE WINDS AS HIGH AS 13-17 KT IN THE OPEN ATLANTIC AND
10-15 KT EARLY IN CHARLESTON HARBOR. THE MAJORITY OF THE WAVE
ENERGY WILL BE A 9-11 SECOND SWELL AROUND 3 OR 4 FT...ATOP A SHORT
PERIOD WIND WAVE. SIGNIFICANT WAVE HEIGHTS WILL AVERAGE 3-4 FT
THROUGHOUT THE NIGHT...WITH EVEN SOME 1-2 FOOTERS NEAR THE MOUTH
OF THE HARBOR. ISOLATED TO SCATTERED SHOWERS WILL PERSIST.

SATURDAY THROUGH WEDNESDAY...A WEAK TROUGH OF LOW PRESSURE LOCATED
OVER THE WATERS WILL SHIFT ONSHORE SATURDAY. A SLIGHTLY TIGHTENED
PRESSURE GRADIENT WILL KEEP EAST WINDS 10-15 KNOTS...WITH SEAS 2-4
FEET IN NEARSHORE WATERS AND 4-5 FEET OFFSHORE WATERS. SURFACE HIGH
PRESSURE WILL THEN DEVELOP SATURDAY NIGHT INTO SUNDAY...ALLOWING
WINDS AND SEAS TO SUBSIDE. THE HIGH WILL PERSIST THROUGH EARLY NEXT
WEEK BEFORE A BACKDOOR COLD FRONT APPROACHES THE WATERS TOWARDS MID
WEEK. AT THIS TIME...CONDITIONS ARE EXPECTED TO REMAIN BELOW
HEADLINE CRITERIA.

RIP CURRENTS...PERSISTENT ONSHORE FLOW WILL RESULT IN AN ELEVATED
RISK OF RIP CURRENTS. A MODERATE RISK OF RIP CURRENTS WILL BE IN
EFFECT FOR ALL BEACHES SATURDAY.

&&

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

&&

$$
SYNOPSIS...
NEAR TERM...
SHORT TERM...ECT
LONG TERM...RJB
AVIATION...ECT/SPR
MARINE...



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