Area Forecast Discussion
Issued by NWS Charleston, SC

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000
FXUS62 KCHS 030836
AFDCHS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
436 AM EDT FRI JUL 3 2015

.SYNOPSIS...
ATLANTIC HIGH PRESSURE WILL PREVAIL AS A TROUGH OF LOW PRESSURE
LINGERS INLAND THROUGH THE MIDDLE OF NEXT WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
A BROAD UPPER LEVEL TROUGH WILL PERSIST OVER THE EASTERN UNITED
STATES...WHILE AT THE SURFACE HIGH PRESSURE WILL CONTINUE TO BUILD
IN FROM THE ATLANTIC AS A PIEDMONT TROUGH REMAINS SITUATED
NORTHWEST OF THE AREA.

THIS MORNING...AN APPROACHING UPPER LEVEL DISTURBANCE EMBEDDED
WITHIN THE LONG WAVE TROUGH HAS GENERATED AN AREA OF SHOWERS AND
THUNDERSTORMS WHICH WILL MOVE FROM EAST-CENTRAL GEORGIA EASTWARD
ACROSS PORTIONS OF THE FORECAST AREA THIS MORNING. THE FORECAST
INDICATES A CHANCE OF SHOWERS AND THUNDERSTORMS TO ACCOUNT FOR
THESE STORMS MOVING THROUGH...AND IT IS POSSIBLE THAT RAINFALL
PROBABILITIES WILL NEED TO BE INCREASED FURTHER AS TRENDS BECOME
FURTHER ESTABLISHED. THESE STORMS ARE NOT ANTICIPATED TO BECOME
SEVERE GIVEN LIMITED INSTABILITY WITH THE ATMOSPHERE HAVING BEEN
SUFFICIENTLY WORKED OVER WITH LAST EVENINGS CONVECTION. SKIES WILL
GENERALLY BE MOSTLY CLOUDY WITH A MIX OF LOW STRATUS AND HIGH
LEVEL CLOUDS AFFECTING THE AREA...BUT PARTIAL CLEARING IS POSSIBLE
LATE THIS MORNING.

THIS AFTERNOON AND EARLY EVENING...ANOTHER IN A SERIES OF UPPER
LEVEL DISTURBANCES WILL APPROACH AND MOVE THROUGH THE AREA...SPARKING
ANOTHER ROUND OF SHOWERS AND THUNDERSTORMS...PRIMARILY ACROSS
SOUTHEAST SOUTH CAROLINA AND PORTIONS OF SOUTHEAST GEORGIA MAINLY
NORTH OF THE I-16 CORRIDOR. HIGH RESOLUTION MESOSCALE MODELS SUCH
AS THE HRRR AND NSSL-WRF INDICATE THIS CONVECTION ORGANIZING INTO
ANOTHER MCS AS IT MOVES THROUGH FROM MID-AFTERNOON THROUGH EARLY
EVENING. THE FORECAST INDICATES SHOWERS AND THUNDERSTORMS BECOMING
LIKELY FROM COLLETON COUNTY NORTH...WITH A CHANCE OF SHOWERS
SOUTHWARD TO I-16...WITH A SLIGHT CHANCE FARTHER SOUTH TO THE
ALTAMAHA RIVER.

MODIFIED SOUNDINGS SHOW SUFFICIENT INSTABILITY DEVELOPING GIVEN SOME
DIURNAL HEATING...WITH SURFACE-BASED CAPE VALUES RISING
POTENTIALLY AS HIGH AS 2500-3000 J/KG. THE PRIMARY THREAT WITH ANY
SEVERE CONVECTION WILL BE DAMAGING WIND GUSTS GIVEN IMPRESSIVE
WIND FIELDS ALOFT FOR THIS TIME OF YEAR. HOWEVER...FREQUENT
LIGHTNING AND TORRENTIAL RAINFALL ARE ALSO EXPECTED. ANY BACKING
OF THE LOW LEVEL WIND FIELD COULD YIELD AN ISOLATED TORNADO...BUT
THE TREAT IS VERY LOW. THE STORM PREDICTION CENTER HAS MOST OF
SOUTHEAST SOUTH CAROLINA IN A SLIGHT RISK...WITH A MARGINAL RISK
DOWN TO I-16...WHICH SEEMS PRUDENT GIVEN THIS SETUP.

DAYTIME HIGHS SHOULD REACH THE LOWER 90S MOST AREAS BEFORE THE
AFTERNOON CONVECTION MOVES IN. EXPECT SOUTHWEST WINDS TO INCREASE
THROUGH THE AFTERNOON...BECOMING RATHER GUSTY AT TIMES.

LATE THIS EVENING AND OVERNIGHT...SOME LINGERING SHOWERS AND
POSSIBLY A FEW THUNDERSTORMS WILL PERSIST...ESPECIALLY NORTH OF
I-16...BEFORE DIMINISHING IN COVERAGE LATE. LOW TEMPERATURES ARE
GENERALLY EXPECTED TO BE IN THE LOWER TO MID 70S.

&&

.SHORT TERM /SATURDAY THROUGH MONDAY/...
GENERALLY THE SAME PATTERN OF OFFSHORE HIGH PRESSURE AND INLAND LOW
PRESSURE TO PERSIST THROUGH THE PERIOD WITH THE TIMING OF UPPER
SHORTWAVES BEING KEY TO RAIN CHANCES.

SATURDAY...INCREASED HIGH PRESSURE RIDGING FROM THE EAST SHOULD KEEP
SHOWER/THUNDERSTORM COVERAGE LOWER THAN PREVIOUS DAYS...WITH THE
HIGHEST CHANCES LIKELY COMING LATER IN THE DAY INTO SATURDAY NIGHT
AS THE UPPER TROUGH AND DEEPER MOISTURE AFFECT THE AREA. HIGHS
LIKELY AT OR JUST ABOVE NORMAL IN THE LOWER TO MID 90S.

SUNDAY...SHOULD BE BETTER RAIN COVERAGE WITH THE UPPER TROUGH A BIT
CLOSER. SEVERE RISK APPEARS LOW OVERALL BUT WILL HAVE TO WATCH HOW
ORGANIZED UPSTREAM CONVECTION BECOMES AS IT PUSHES EAST TOWARD THE
COAST. HIGHS LIKELY SLIGHTLY BELOW NORMAL. SOME SHOWERS AND STORMS
WILL LINGER INTO SUNDAY NIGHT.

MONDAY...SCATTERED TO POSSIBLY NUMEROUS SHOWERS AND THUNDERSTORMS
EXPECTED AGAIN WITH ABUNDANT CLOUDS LIKELY HELPING KEEP
TEMPERATURES SLIGHTLY BELOW NORMAL.

&&

.LONG TERM /MONDAY NIGHT THROUGH THURSDAY/...
MEDIUM RANGE GUIDANCE IS IN FAIRLY GOOD AGREEMENT THROUGH MID WEEK
INDICATING THE UPPER TROUGH OVER THE EAST COAST WILL BREAK DOWN AND
GIVE WAY TO HIGH PRESSURE. THIS PATTERN WILL FAVOR CHANCES OF MAINLY
DIURNALLY DRIVEN SHOWERS AND THUNDERSTORMS EACH DAY...WITH THE
GREATEST COVERAGE LIKELY TUESDAY. TEMPERATURES WILL GENERALLY BE
NEAR NORMAL...WITH HIGHS IN THE LOWER TO MID 90S AND LOWS IN THE
LOWER TO MID 70S.

&&

.AVIATION /08Z FRIDAY THROUGH TUESDAY/...
KCHS...HIGH RESOLUTION MESOSCALE MODELS INDICATE ISOLATED SHOWERS
ASSOCIATED WITH AN UPPER LEVEL DISTURBANCE COULD AFFECT THE
TERMINAL IN THE 11-14Z TIME FRAME...THUS HAVE ADDED A TEMPO GROUP
FOR LIGHT SHOWERS DURING THAT PERIOD. A THUNDERSTORM IS CERTAINLY
POSSIBLE AS WELL BUT CONFIDENCE IS NOT HIGH ENOUGH TO INCLUDE
MENTION AT THIS TIME. THEN...CONFIDENCE IS INCREASING THAT
STRONGER CONVECTION COULD IMPACT THE TERMINAL LATE THIS AFTERNOON
INTO EARLY THIS EVENING AND THE FORECAST HAS A TEMPO GROUP FOR
THUNDERSTORMS FROM 19-23Z WITH FLIGHT RESTRICTIONS AND GUSTY
WINDS LIKELY TO ACCOMPANY ANY THUNDERSTORMS. LINGERING SHOWERS ARE
THEN EXPECTED THROUGH MUCH OF THE EVENING.

KSAV...SOME PATCHY LOW STRATUS HAS DEVELOPED AT THE TERMINAL DUE
TO LINGERING BOUNDARY LAYER MOISTURE AND PARTIAL CLEARING OF HIGH
CLOUDS. IT IS VERY POSSIBLE THAT A BRIEF PERIOD OF IFR CEILINGS
COULD OCCUR THROUGH 14Z AND AMENDMENTS MAY BE NECESSARY BASED ON
SATELLITE TRENDS. HIGH RESOLUTION MESOSCALE MODELS INDICATE
ISOLATED SHOWERS ASSOCIATED WITH AN UPPER LEVEL DISTURBANCE COULD
AFFECT THE TERMINAL IN THE 10-14Z TIME FRAME...THUS HAVE ADDED A
TEMPO GROUP FOR LIGHT SHOWERS DURING THAT PERIOD. A THUNDERSTORM
IS CERTAINLY POSSIBLE AS WELL BUT CONFIDENCE IS NOT HIGH ENOUGH TO
INCLUDE MENTION AT THIS TIME. CONVECTION LATER THIS AFTERNOON AND
EARLY THIS EVENING IS EXPECTED TO PRIMARILY REMAIN NORTH OF THE
TERMINAL SO HAVE NO MENTION IN THE FORECAST...BUT THIS WILL NEED
TO BE REEVALUATED WITH EACH FORECAST UPDATE AS TRENDS BECOME MORE
APPARENT.

EXTENDED AVIATION OUTLOOK...BRIEF FLIGHT RESTRICTIONS ARE
POSSIBLE IN MAINLY AFTERNOON/EARLY EVENING SHOWERS AND
THUNDERSTORMS...WITH THE BEST CHANCES BEGINNING SUNDAY.
OTHERWISE...VFR CONDITIONS ARE EXPECTED TO PREVAIL.


&&

.MARINE...
TODAY AND TONIGHT...THE SURFACE PRESSURE GRADIENT WILL TIGHTEN
BETWEEN A PIEDMONT TROUGH NORTHWEST OF THE AREA AND HIGH PRESSURE
OVER THE ATLANTIC. UNUSUALLY STRONG WIND FIELDS ALOFT COMBINED
WITH THE TIGHT GRADIENT WILL SUPPORT WINDS UPWARDS OF 15-20 KT
OVER MUCH OF THE WATERS LATER THIS AFTERNOON INTO TONIGHT...ESPECIALLY
AS NOCTURNAL JETTING DEVELOPS. A SMALL CRAFT ADVISORY HAS BEEN
ISSUED BEGINNING MID-AFTERNOON FOR CHARLESTON HARBOR AND THE
CHARLESTON COUNTY COASTAL WATERS...THEN FOR THE OUTER GEORGIA
WATERS BY EARLY THIS EVENING AS FREQUENT GUSTS TO 25 KT ARE
EXPECTED TO DEVELOP OVER THESE WATERS. WINDS SHOULD DIMINISH IN
THE HARBOR DURING THE EVENING...THEN LATE TONIGHT OVER THE COASTAL
WATERS. SEAS WILL BUILD AS HIGH AS 3-5 FT...HIGHEST OVER THE OUTER
GEORGIA WATERS.

SATURDAY THROUGH WEDNESDAY...A PERSISTENT PATTERN FEATURING ATLANTIC
HIGH PRESSURE AND AN INLAND TROUGH OF LOW PRESSURE EXPECTED. A
TIGHTENED PRESSURE GRADIENT BETWEEN THESE FEATURES WILL MAINTAIN
ELEVATED WINDS/SEAS THROUGH THE PERIOD BUT CONDITIONS SHOULD LARGELY
REMAIN BELOW ADVISORY LEVELS. SEAS WILL BE 2-4 FEET ON AVERAGE...BUT
COULD REACH 5 FT AT TIMES MOSTLY BEYOND 20 NM.

RIP CURRENTS...ELEVATED S/SW WINDS AND ASTRONOMICAL FACTORS WILL
RESULT IN A MODERATE RISK FOR RIP CURRENTS ALONG THE LOWER SOUTH
CAROLINA COAST TODAY. AN ELEVATED RISK FOR RIP CURRENTS COULD
THEN PERSIST INTO THE FOURTH OF JULY WEEKEND.

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
SC...NONE.
MARINE...SMALL CRAFT ADVISORY FROM 3 PM THIS AFTERNOON TO 8 PM EDT THIS
     EVENING FOR AMZ330.
     SMALL CRAFT ADVISORY FROM 6 PM THIS EVENING TO 5 AM EDT
     SATURDAY FOR AMZ374.
     SMALL CRAFT ADVISORY FROM 3 PM THIS AFTERNOON TO 5 AM EDT
     SATURDAY FOR AMZ350.

&&

$$

NEAR TERM...JAQ
SHORT TERM...RJB
LONG TERM...RJB
AVIATION...JAQ/RJB
MARINE...JAQ/RJB



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