Area Forecast Discussion
Issued by NWS Charleston, SC

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000
FXUS62 KCHS 291450
AFDCHS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
1050 AM EDT WED JUL 29 2015

.SYNOPSIS...
A WEAK PRESSURE PATTERN WILL PERSIST OVER THE REGION INTO EARLY
THURSDAY. A COLD FRONT WILL ADVANCE INTO THE REGION FRIDAY AND
WILL STALL THROUGH EARLY NEXT WEEK. HIGH PRESSURE WILL GRADUALLY
INTO THE REGION BY THE MIDDLE OF NEXT WEEK.

&&

.NEAR TERM /THROUGH TONIGHT/...
LATE THIS MORNING...ALOFT THE FORECAST AREA WILL BE POSITIONED
IN THE NORTHERLY DEEP LAYER FLOW BETWEEN THE EXPANSIVE UPPER
RIDGE TO THE WEST AND A BROAD UPPER LOW WELL TO THE EAST. THE
PRESSURE PATTERN WILL REMAIN QUITE WEAK WITHIN A RATHER ILL-
DEFINED AREA OF LOW PRESSURE. THE MAIN SURFACE LOWS ARE WELL
OFFSHORE...AS SEEN IN VISIBLE SATELLITE IMAGERY...AND WE WILL SEE
ANOTHER WEAK LOW INLAND THIS AFTERNOON. SHOWERS ARE ALREADY
ONGOING WELL TO THE WEST MAINLY IMPACTING JENKINS COUNTY AT THE
MOMENT. BASED ON THE SPREAD OF MODEL RUNS AND MODEL SOUNDINGS...IT
LOOKS LIKE THE BULK OF ANY SHOWER/THUNDERSTORM ACTIVITY WILL TAKE
PLACE WELL WEST OF I-95 TODAY. SOUNDINGS SHOW A CONSIDERABLE CAP
ACROSS MUCH OF SOUTHEAST SOUTH CAROLINA TODAY...AND THAT SHOULD
KEEP COVERAGE MINIMAL AT BEST. THE SEVERE WEATHER THREAT IS QUITE
MINIMAL WITH VERY WEAK MID LEVEL LAPSE RATES. HIGHS LOOK ON TRACK
FOR THE LOW TO MID 90S EVERYWHERE AWAY FROM THE BEACHES.

TONIGHT...A FEW SHOWERS AND TSTMS MAY LINGER INTO MID EVENING
INLAND ZONES WEST OF I-95 BUT CONDITIONS SHOULD BE QUIET WITH
PARTLY CLOUDY SKIES AND PERHAPS SOME LATE NIGHT FOG AND
STRATUS...MAINLY OVER INLAND ZONES.

&&

.SHORT TERM /THURSDAY THROUGH SATURDAY/...
THURSDAY...AN EAST-WEST MOISTURE GRADIENT WILL PERSIST OVER THE
REGION. THUS...AFTERNOON POPS ARE GRADUATED FROM SLIGHT CHANCE NEAR
THE COAST TO CHANCE INLAND...HIGHEST ALONG/WEST OF I-95. MODELS
DEPICT LESS THAN IMPRESSIVE INLAND INSTABILITY. THUS...THE POTENTIAL
FOR SEVERE WEATHER SHOULD REMAIN QUITE LIMITED...UNLESS A STRONGER
MULTICELL THUNDERSTORM CLUSTER WHICH DEVELOPS INLAND CLIPS FAR
INLAND COUNTIES. OUTSIDE THUNDERSTORMS/BEFORE THUNDERSTORMS
DEVELOP...TEMPERATURES IN THE MID 90S SHOULD BECOME COMMON AWAY FROM
THE COAST...AND HEAT INDEX VALUES COULD PEAK IN THE 100-105F RANGE
AT MANY LOCATIONS.

THURSDAY NIGHT...INLAND THUNDERSTORM COVERAGE/INTENSITY SHOULD
GRADUALLY WANE. HOWEVER...TO VARYING DEGREES GUIDANCE DEPICTS
SUFFICIENT MOISTURE SPREADING INTO THE REGION FROM THE
NORTH/NORTHWEST TO SUPPORT ISOLATED SHOWERS/THUNDERSTORMS THROUGH
THE OVERNIGHT. THUS...MAINTAINED ONGOING SLIGHT CHANCE POPS AFTER
MIDNIGHT.

FRIDAY AND SATURDAY...A COLD FRONT WILL ADVANCE INTO THE REGION AND
WILL STALL. THE ASSOCIATED TROUGH AT THE SURFACE AND ALOFT WILL
SETTLE OVER THE REGION AND WILL FOCUS A POOL OF PWATS EXCEEDING 2
INCHES...1-3 STANDARD DEVIATIONS ABOVE NORMAL...OVER THE AREA. THIS
REGIME WILL SUPPORT PERIODS OF ACTIVE CONVECTION FEATURING LIKELY
POPS ACROSS MANY AREAS ESPECIALLY FRIDAY AFTERNOON/EVENING AND AGAIN
SATURDAY AFTERNOON/EVENING. LOCALLY GREATER POPS COULD EVENTUALLY BE
REQUIRED.

THE POTENTIAL FOR PULSE SEVERE WEATHER COULD ACTUALLY BE GREATEST AS
THUNDERSTORMS FIRE AND EXPAND IN COVERAGE FRIDAY AFTERNOON. OF
GREATER CONCERN...HIGH PWATS AND WEAK TROPOSPHERIC WINDS WILL
SUPPORT HIGH RAINFALL RATES AND ERRATIC STORM PROPAGATION...AND THE
PROBABILITY FOR LOCALIZED EXCESSIVE RAINFALL/FLOODING WILL INCREASE.
OTHERWISE...TEMPERATURES COULD TOP OUT IN THE LOWER/MID 90S BEFORE
THUNDERSTORMS DEVELOP FRIDAY. THEN...HELD TEMPERATURES CLOSE TO 90F
SATURDAY...ALTHOUGH TEMPERATURES COULD HOLD IN THE 80S AT MANY
LOCATIONS.

&&

.LONG TERM /SATURDAY NIGHT THROUGH TUESDAY/...
THE STATIONARY FRONT...ASSOCIATED DEEP LAYERED TROUGH...WEAK
STEERING WINDS AND RESERVOIR OF ABOVE-NORMAL PWATS WILL PERSIST OVER
THE REGION THROUGH THE WEEKEND AND INTO EARLY NEXT WEEK. THIS
ENVIRONMENT WILL SUPPORT ELEVATED POPS AND A CONTINUING THREAT FOR
LOCALLY HEAVY RAINFALL/SHORT FUSE FLOODING. LIKELY POPS APPEAR
REASONABLE FOR SATURDAY. THEN...MODEL DISAGREEMENT ARISES REGARDING
THE POSITION OF THE TROUGH AND ASSOCIATED AXIS OF DEEPEST MOISTURE
SUNDAY-MONDAY. IF THE ATLANTIC RIDGE ALLOWS THE TROUGH AXIS TO PUSH
OFF THE COAST...THE FOCUS FOR HEAVIEST RAIN WILL SHIFT OVER THE
ATLANTIC WATERS. HOWEVER...IF THE ATLANTIC RIDGE REMAINS STRONGER
AND HOLDS THE TROUGH AXIS AND RICH MOISTURE OVER THE REGION AS
DEPICTED BY THE 29/00Z EUROPEAN...ELEVATED POPS/THE ASSOCIATED
POTENTIAL FOR LOCALLY HEAVY RAIN WILL PERSIST. DUE TO
UNCERTAINTY...CAPPED MAXIMUM POPS AT AROUND 50 PERCENT SUNDAY AND
MONDAY. EVENTUALLY...THE TROUGH WILL EVENTUALLY WEAKEN OR WILL SHIFT
OFFSHORE...ALLOWING HIGH PRESSURE TO GRADUALLY BUILD INTO THE REGION
WITH MORE TYPICAL TEMPERATURES/POPS TUESDAY THROUGH WEDNESDAY.

&&

.AVIATION /15Z WEDNESDAY THROUGH SUNDAY/...
VFR CONDITIONS EXPECTED TO PREVAIL TODAY AND MUCH OF TONIGHT AT
BOTH KSAV/KCHS. CONVECTION IS EXPECTED TO DEVELOP INLAND FROM THE
TERMINALS LATER THIS AFTERNOON AND EVENING. AREAS OF LOW CLOUDS
ARE POSSIBLE OVERNIGHT BUT FOG IS FAIRLY UNLIKELY.

EXTENDED AVIATION OUTLOOK...LOW CHANCE FOR DIRECT IMPACTS FROM
THUNDERSTORMS THURSDAY...THEN INCREASING THUNDERSTORM CHANCES
FRIDAY THROUGH THE WEEKEND.

&&

.MARINE...
TODAY AND TONIGHT...WITH THE WEAK LOW PRESSURE WELL
OFFSHORE...ONSHORE FLOW WILL GENERALLY PERSIST WITH SPEEDS MAINLY
IN THE 10 KT RANGE THROUGH TONIGHT WITH DIURNAL ENHANCEMENTS OF
10-15 KT ALONG COASTAL CHARLESTON COUNTY THIS AFTERNOON AND
EVENING. SEAS 2 TO 3 FT THROUGH TONIGHT...HIGHEST BEYOND 20 NM
OFFSHORE.

AS A COLD FRONT APPROACHES THEN STALL OVER THE REGION...WINDS WILL
GRADUALLY VEER TOWARD THE SOUTH/SOUTHWEST LATE WEEK INTO EARLY NEXT
WEEKEND. WHILE WIND SPEEDS WILL GENERALLY BE LESS THAN 15 KNOTS...
THE SEA BREEZE CIRCULATION AND PERIODIC NOCTURNAL SURGES COULD PUSH
WINDS TO 15-20 KNOTS. SEAS OF 2 TO 3 FEET WILL REMAIN COMMON...
ALTHOUGH PERIODS OF 4 FT SEAS COULD OCCUR ESPECIALLY AT 20 NM AND
BEYOND. ALSO...THUNDERSTORMS ARE EXPECTED AT ANY TIME LATE WEEK INTO
EARLY NEXT WEEK. THUNDERSTORMS COULD GREATLY ALTER SYNOPTIC WINDS
AND WILL CREATE LOCALIZED HAZARDS...PERHAPS INCLUDING WATERSPOUTS.

&&

.TIDES/COASTAL FLOODING...
ELEVATED HIGH TIDE LEVELS ARE EXPECTED THROUGH THE REST OF THE
WEEK AND THE WEEKEND THANKS TO THE UPCOMING PERIGEAN SPRING TIDE
AND FULL MOON CYCLE. ONSHORE WINDS WILL ALSO PROVIDE ADDITIONAL
ENHANCEMENT AT TIMES...AND SHALLOW COASTAL FLOODING WILL BE
POSSIBLE THROUGH THE WEEKEND ESPECIALLY WITH THE EVENING HIGH TIDE
CYCLE. WILL MAINTAIN THE MENTION IN THE HAZARDOUS WEATHER
OUTLOOK. A COASTAL FLOOD ADVISORY COULD BE ISSUED AROUND HIGH
TIDE LATE THIS AFTERNOON INTO EARLY THIS EVENING FOR DOWNTOWN
CHARLESTON.

&&

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

&&

$$

NEAR TERM...BSH
SHORT TERM...SPR
LONG TERM...SPR
AVIATION...
MARINE...SPR
TIDES/COASTAL FLOODING...



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