Area Forecast Discussion
Issued by NWS Charleston, SC

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FXUS62 KCHS 030544
AFDCHS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
144 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 /UNTIL 6 AM THIS MORNING/...
EARLY THIS MORNING...THE EARLIER CONVECTION HAS SHIFTED WELL
OFFSHORE WITH RAIN-FREE CONDITIONS IN PLACE ACROSS THE AREA. HIGH
LEVEL CLOUDS CONTINUE TO THIN/DISSIPATE...BUT LOW STRATUS IS
BEGINNING TO DEVELOP WHERE BREAKS IN THE CLOUD COVER OCCUR DUE TO
MOIST BOUNDARY LAYER CONDITIONS. ISOLATED CONVECTION ACROSS THE
UPSTATE OF SOUTH CAROLINA AND ACROSS EAST-CENTRAL GEORGIA CONTINUE
TO TRACK TOWARD THE AREA.

THROUGH DAYBREAK...THE UPSTREAM CONVECTION ASSOCIATED WITH THE
NEXT IN A SERIES OF UPPER LEVEL DISTURBANCES WILL LIKELY SHIFT
INTO THE AREA FROM THE WEST TOWARD DAYBREAK AND THE FORECAST
INDICATES A SLIGHT CHANCE OF SHOWERS AND THUNDERSTORMS AS A
RESULT. ANY BREAKS IN THE CLOUD COVER SHOULD EITHER FILL IN WITH
DEVELOPING LOW STRATUS OR HIGH LEVEL CLOUDS SHIFTING IN FROM THE
WEST...THUS KEEPING SKIES AT LEAST MOSTLY CLOUDY. TEMPERATURES
WILL REMAIN NEARLY STEADY OR ONLY SLOWLY FALL BY ANOTHER DEGREE OR
TWO.

&&

.SHORT TERM /6 AM THIS MORNING THROUGH SUNDAY/...
THIS PERIOD WILL FEATURE MAINLY SUBTLE CHANGES WHICH WILL TRANSLATE
IN VARYING THUNDERSTORM POTENTIAL.

A BROAD UPPER TROUGH WILL REMAIN IN PLACE FRIDAY. ELEVATED LOWER/MID
TROPOSPHERIC WINDS...VORTICITY MAXIMA EMBEDDED WITHIN THE LONGWAVE
TROUGH...INSTABILITY AND MESOSCALE BOUNDARIES WILL SUPPORT MULTICELL
CLUSTERS OF THUNDERSTORMS WHICH WILL PROPAGATE FROM EAST TO WEST.
PER 02/12Z GUIDANCE MAINTAINED AFTERNOON/EARLY EVENING POPS
GRADUATED FROM LIKELY NORTH TO CHANCE SOUTH/WEST. THE COMBINATION OF
ELEVATED WINDS/SHEAR AND INSTABILITY WILL SUPPORT AT LEAST
ISOLATED/SPORADIC EPISODES OF SEVERE WEATHER...ESPECIALLY DAMAGING
WIND GUSTS.

POPS GRADUALLY DECREASE/RETREAT TOWARD THE COAST/ADJACENT COASTAL
WATERS FRIDAY NIGHT. THEN...DURING THE FOURTH OF JULY THE ATLANTIC
RIDGE SHOULD EXPAND INTO THE REGION AS THE UPPER TROUGH
AMPLIFIES/SHARPENS UPSTREAM. THUS...LIMITED POPS TO SLIGHT CHANCE
SATURDAY AFTERNOON...AND TEMPERATURES WILL RECOVER INTO THE
LOWER/MID 90S.

SATURDAY NIGHT AND SUNDAY...THE UPSTREAM UPPER TROUGH WILL PRESS
E/SE TOWARD THE REGION...NUDGING THE ATLANTIC RIDGE OFFSHORE. THIS
COULD PROMOTE THUNDERSTORMS...EITHER DEVELOPING IN PLACE OVER THE
REGION OR ONGOING/UPSTREAM CONVECTIVE COMPLEXES PROPAGATING INTO THE
FORECAST AREA AS EARLY AS LATER SUNDAY NIGHT. ACCORDINGLY...RAISED
POPS TO SLIGHT CHANCE LATE SUNDAY NIGHT. SUNDAY AFTERNOON COULD
BECOME QUITE ACTIVE AS ONE OR MORE MULTICELL CLUSTERS OF
THUNDERSTORMS WITH AT LEAST AN ISOLATED SEVERE THREAT PUSH INTO THE
FORECAST AREA. RAISED MAX POPS INTO THE 45-50 PERCENT RANGE SUNDAY
AFTERNOON...BUT LOCALLY GREATER POPS COULD EVENTUALLY BE REQUIRED.

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
MEDIUM RANGE GUIDANCE IS IN FAIRLY GOOD AGREEMENT THROUGH THE LONG
TERM PERIOD. AN UPPER LEVEL TROUGH WILL DEEPEN OVER THE SOUTHEAST
STATES AND PERSIST THROUGH MID-WEEK. MEANWHILE AT THE SURFACE...
ATLANTIC HIGH PRESSURE WILL PREVAIL AS A PIEDMONT TROUGH PERSISTS
INLAND. THIS PATTERN WILL FAVOR CHANCES OF MAINLY DIURNALLY DRIVEN
SHOWERS AND THUNDERSTORMS EACH DAY...WITH THE GREATEST COVERAGE
LIKELY TO OCCUR MONDAY AND TUESDAY. TEMPERATURES WILL GENERALLY BE
NEAR NORMAL...WITH HIGHS AROUND 90 OR IN THE LOWER 90S AND LOWS IN
THE LOWER TO MID 70S.

&&

.AVIATION /06Z 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
STRONGERCONVECTION 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 ISOLATED TO SCATTERED SHOWERS AND
THUNDERSTORMS. OTHERWISE...VFR CONDITIONS ARE GENERALLY EXPECTED TO
PREVAIL.

&&

.MARINE...
TONIGHT...ATLANTIC HIGH PRESSURE WILL DOMINATE THE WEATHER
PATTERN OVER THE COASTAL WATERS WITH A PIEDMONT TROUGH SITUATED
INLAND. IN GENERAL...SOUTH/SOUTHWEST WINDS WILL REMAIN AT OR BELOW
15-20 KTS DURING NOCTURNAL LOW LEVEL JETTING. SEAS WILL RANGE
BETWEEN 2-4 FT. WINDS AND SEAS WILL VARY WITHIN THUNDERSTORMS THIS
EVENING AND OVERNIGHT.

FRIDAY THROUGH WEDNESDAY...A PERSISTENT PATTERN FEATURING ATLANTIC
HIGH PRESSURE AND AN INLAND SURFACE TROUGH WILL CONTINUE WITH ONLY
MINOR FLUCTUATIONS. A TIGHTENED PRESSURE GRADIENT BETWEEN THE TWO
FEATURES WILL MAINTAIN ELEVATED WINDS/SEAS THROUGH THE PERIOD. IN
FACT...IT APPEARS THAT CONDITIONS COULD REACH MARGINAL SMALL CRAFT
ADVISORY CRITERIA OVER A PORTION OF THE WATERS...ESPECIALLY ACROSS
AMZ350 AND AMZ374...FRIDAY NIGHT. OTHERWISE...SEA BREEZE
CIRCULATIONS AND NOCTURNAL LOW LEVEL JETTING WILL ALLOW
SOUTH/SOUTHWEST WINDS TO PEAK NEAR 15-20 KTS. SEAS WILL BE 2-4 FEET
ON AVERAGE...BUT COULD REACH 5 FT IN THE OUTER PORTIONS OF THE
WATERS DURING NOCTURNAL SURGES.

RIP CURRENTS...ELEVATED S/SW WINDS AND ASTRONOMICAL FACTORS WILL
CONTINUE ESPECIALLY ALONG THE CHARLESTON COUNTY COAST FRIDAY.
THUS...WILL ONCE AGAIN INDICATE A MODERATE RISK FOR RIP CURRENTS
HERE FRIDAY. AN ELEVATED RISK FOR RIP CURRENTS COULD THEN PERSIST
INTO THE FOURTH OF JULY WEEKEND.

&&

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

&&

$$

NEAR TERM...JAQ
SHORT TERM...SPR
LONG TERM...JAQ
AVIATION...JAQ/SPR
MARINE...DPB/SPR


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