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Area Forecast Discussion

853
FXUS62 KCHS 300236
AFDCHS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
1036 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/...
QUICK UPDATE TO END SHOWERS OVER COASTAL GA FOR THE NEXT FEW
HOURS...AND TO DELAY THE RETURN OF ACTIVITY ONSHORE A BIT LATER
TONIGHT.

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/MASS 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
MAYBE 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...PARTLY TO MOSTLY CLOUDY SKY COVER 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 /03Z SATURDAY THROUGH WEDNESDAY/...
VFR CONDITIONS AT KSAV AND KCHS FOR MOST OF THE VALID CYCLE
THROUGH 00Z SUNDAY. HOWEVER...WITH THE APPROACH OF A COASTAL
TROUGH EARLY SATURDAY AND THEN THE FORMATION OF THE SEA BREEZE
THERE WILL BE ISOLATED TO SCATTERED SHRA THAT DEVELOP. ODDS OF ANY
DIRECT IMPACTS AT EITHER TERMINAL IS TOO LOW TO CARRY ANYTHING
MORE THAN VCSH WITH THE 00Z FORECAST. ADJUSTMENTS CAN BE MADE IN
FUTURE UPDATES. EASTERLY WINDS WILL DIMINISH THIS EVENING...THEN
REMAIN LIGHT MUCH OF TONIGHT INTO EARLY SATURDAY...BEFORE EAST/SE
WINDS BECOME GUSTY IN WAKE OF THE SEA BREEZE BOUNDARY SATURDAY
AFTERNOON/EVENING AT BOTH AIRFIELDS.

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

&&

.MARINE...
TONIGHT...A SPRAWLING RIDGE OF ATLANTIC HIGH PRESSURE ACROSS THE
WATERS WILL GIVE WAY TO AN INVERTED TROUGH THAT FORMS ACROSS THE
MARINE COMMUNITY AROUND 04-08Z 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...
MARINE...



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