Area Forecast Discussion
Issued by NWS Charleston, SC

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FXUS62 KCHS 012342
AFDCHS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
742 PM EDT SAT AUG 1 2015

.SYNOPSIS...
A STATIONARY FRONT WILL DISSIPATE OVER THE AREA THROUGH SUNDAY AS
HIGH PRESSURE BUILDS IN EARLY NEXT WEEK. AN INLAND LOW PRESSURE
TROUGH WILL THEN DEVELOP BY LATE NEXT WEEK.

&&

.NEAR TERM /UNTIL 6 AM SUNDAY MORNING/...
MOST OF THE MEASURABLE RAINFALL HAS ENDED FOR THIS EVENING. A FEW
LINGERING SHOWERS WILL IMPACT PARTS OF LONG AND TATTNALL COUNTIES
THROUGH 8 PM. EXPECT DRY CONDITIONS TO PREVAIL FOR THE REST OF
THE NIGHT FOR MOST AREAS. THERE ARE SIGNALS IN THE VARIOUS HIGH
RESOLUTION GUIDANCE THAT ISOLATED TO PERHAPS SCATTERED SHOWERS/TSTMS
COULD REDEVELOP ALONG THE GEORGIA COAST AFTER 3-4 AM AS LOW-LEVEL
JETTING INTENSIFIES AND INTERACTS WILL A MODEST AMOUNT OF
INSTABILITY THAT LINGERS JUST OFFSHORE. THE RAP IS MUCH MORE
EMPHATIC ON THE REDEVELOPMENT OF DEEP CONVECTION PRIOR TO
SUNRISE...WHILE THE H3R IS LESS SO. WILL SHOW POPS INCREASING TO
20-40 PERCENT DURING THIS TIME ROUGHLY ALONG AND SOUTH OF HILTON
HEAD-LUDOWICI LINE...HIGHEST ACROSS COASTAL MCINTOSH COUNTY...WITH
DRY CONDITIONS ELSEWHERE TO TREND. IF THE H3R BEGINS TO COME MORE
IN LINE WITH THE LATEST RAP...THEN AN INCREASE IN POPS MAY BE IN
ORDER LATER THIS EVENING.

CONDITIONS WILL FAVOR THE FORMATION AND SLOW EXPANSION OF LOW
STRATUS AND FOG EARLY SUNDAY AS LOW-LEVEL JETTING TAKES HOLD. THE
RISK FOR FOG WILL BE HIGHEST ACROSS INTERIOR SOUTHEAST SOUTH
CAROLINA CLOSEST TO THE WEAK STATIONARY FRONT...WHILE STRATUS IS
MORE LIKELY FAR SOUTH AND CLOSER TO THE COAST. IT IS UNCLEAR
EXACTLY HOW WIDESPREAD EITHER ELEMENT WILL BECOME THIS FAR OUT SO
ADJUSTMENTS WILL LIKELY BE NEEDED THROUGHOUT THE NIGHT AS TRENDS
BECOME MORE APPARENT.

&&

.SHORT TERM /6 AM SUNDAY MORNING THROUGH TUESDAY/...
SUNDAY THROUGH TUESDAY...OVERALL THE PATTERN WILL NOT CHANGE
APPRECIABLY THROUGH EARLY NEXT WEEK. ALOFT...THE FORECAST AREA WILL
BE POSITIONED ON THE SOUTHERN EXTENT OF TROUGHING ACROSS THE GREAT
LAKES AND NORTHEAST. THIS WILL RESULT IN A RATHER WEAK AND NEBULOUS
NEARLY ZONAL FLOW THROUGH THE PERIOD. AT THE SURFACE...THE NEARLY
STATIONARY FRONT WILL DISSIPATE AND ITS REMNANTS WILL LINGER ALONG
THE COASTLINE SUNDAY AND MONDAY. THIS WILL RESULT IN A RATHER TIGHT
PWAT GRADIENT ACROSS THE FORECAST AREA...RANGING FROM AROUND 1.5
INCHES OR LESS AROUND ALLENDALE TO WELL OVER 2 INCHES OVER THE
ATLANTIC COASTAL WATERS. BY TUESDAY THE DEEP MOISTURE WILL PUSH EVEN
FURTHER OFFSHORE AND MUCH DRIER AIR WILL COVER ALL OF THE REGION.
POPS FOR SUNDAY AND MONDAY ARE FOCUSED ALONG THE COAST AND OVER THE
COASTAL WATERS...WITH FURTHER DECREASING COVERAGE BY TUESDAY. POPS
MAY BE A BIT OVERDONE FURTHER INLAND AT TIMES...BUT IT WOULDN/T
REQUIRE A SIGNIFICANT SHIFT IN THE DEEP MOISTURE AXIS TO WARRANT
RAISING POPS. TEMPERATURES ARE PRETTY SIMILAR TO WHAT THEY HAVE BEEN
FOR THE LAST FEW DAYS. LOW TO MID 90S SUNDAY AND MONDAY WITH A
SLIGHT WARMING TREND BY TUESDAY.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SATURDAY/...
UPPER SHORTWAVE ENERGY WILL BEGIN MOVING INTO THE SOUTHEAST UNITED
STATES MID TO LATE WEEK WITH A PRONOUNCED SURFACE TROUGH DEVELOPING
INLAND. PWATS WILL RETURN TO A MORE TYPICAL 2" FOR EARLY AUGUST BY
THURSDAY. A COLD FRONT MAY AFFECT THE AREA FRIDAY INTO SATURDAY. WE
HAVE INCREASING POPS DURING THIS PERIOD AND SLIGHTLY MODERATED
TEMPERATURES DUE TO THICKER CLOUD COVER.

&&

.AVIATION /00Z SUNDAY THROUGH THURSDAY/...
TSTM IMPACTS AT BOTH TERMINALS HAS ENDED. PRIMARY CONCERN
OVERNIGHT IS THE POTENTIAL FOR FOG/STRATUS IMPACTING KCHS/KSAV.
THE RISK FOR LOW STRATUS LOOKS HIGHEST AT KSAV AS LOW-LEVEL
JETTING TAKES HOLD AN INTERACTS WITH RICH LOW-LEVEL MOISTURE WHILE
FOG IS MORE LIKELY AT KCHS. THE DEGREE OF JETTING WILL ULTIMATELY
DETERMINE HOW IMPACTFUL EITHER ELEMENT WILL BECOME AT THE
TERMINALS. WILL CONTINUE TO TAKE A TRENDED YET CONSERVATIVE
APPROACH WITH THE 00Z TAF CYCLE. WILL CALL FOR LOW-END MVFR CIGS
09-14Z WITH VERY LIGHT FOG AT KSAV...WHILE A TEMPO GROUP FOR MVFR
VSBYS FROM 09-12Z WILL BE SHOWN AT KCHS. ADJUSTMENTS WILL MOST
LIKELY BE NEEDED AS TRENDS BECOME MORE APPARENT LATER TONIGHT.
ONCE FOG/STRATUS DISSIPATES...EXPECT VFR CONDITIONS.

EXTENDED AVIATION OUTLOOK...LOW CHANCES FOR DIRECT IMPACTS FROM
AFTERNOON/EVENING SHOWERS AND THUNDERSTORMS. ALSO LOW CHANCES FOR
PERIODS OF STRATUS/FOG AROUND SUNRISE.

&&

.MARINE...
TONIGHT...VARIABLE WINDS THIS AFTERNOON TO BECOME SOUTHWEST AND
STRENGTHEN THIS EVENING AS THE LOW-LEVEL JET INTENSIFIES AHEAD OF
LOW PRESSURE OVER THE WESTERN FLORIDA PANHANDLE. THERE IS A
CHANCE THAT SMALL CRAFT ADVISORY CONDITIONS DEVELOP OVER EASTERN
PORTION OF THE OUTER GEORGIA WATERS CLOSER TO THE GULF STREAM BUT
FOR NOW WE KEPT CONDITIONS JUST BELOW SUCH LEVELS /20 KT AND 5
FT/.

SUNDAY THROUGH THURSDAY...THE LINGERING WEAK FRONT WILL DISSIPATE
ALONG THE COAST ON SUNDAY AND SOUTHWEST FLOW WILL GENERALLY PREVAIL
ACROSS THE LOCAL WATERS THROUGH THE MIDDLE OF NEXT WEEK. AS AN
INLAND TROUGH OF LOW PRESSURE DEVELOPS...THE PRESSURE GRADIENT WILL
TIGHTEN AT TIMES AND LEAD TO PERIODS OF SURGING IN THE SOUTHWEST
FLOW. WIND SPEEDS WILL GENERALLY TOP OUT IN THE 15-20 KT RANGE...BUT
COULD MARGINALLY APPROACH SMALL CRAFT ADVISORY CRITERIA AT TIMES.
SEAS WILL INCREASE IN THE IMPROVING SOUTHWEST FETCH AS
WELL...INCREASING TO 2-4 FT WITHIN 20 NM AND MAINLY 4-5 FT BEYOND. 6
FT SEAS COULD BEGIN ACROSS THE OUTER GEORGIA WATERS STARTING MONDAY
AND A SMALL CRAFT ADVISORY COULD BE NEEDED.

&&

.TIDES/COASTAL FLOODING...
CURRENT TIDE TRENDS SUGGEST LEVELS COULD GET IN THE 6.9-7.0 FT
MLLW RANGE AT THE CHARLESTON HARBOR WITH HIGH TIDE THIS EVENING.
NOT YET CONFIDENT ENOUGH THAT 7.0 FT ADVISORY CRITERIA WILL BE
BREACHED...SO HAVE ISSUED A COASTAL FLOOD STATEMENT TO ADDRESS
VERY MINOR FLOODING ISSUES THAT ARE KNOWN TO OCCUR IN DOWNTOWN
CHARLESTON WITH TIDES FALLING JUST SHORT OF 7.0 FT MLLW. THE NEED
FOR A COASTAL FLOOD ADVISORY CONTINUES TO BE EVALUATED.

TIDES WILL REMAIN ELEVATED THROUGH SUNDAY...BUT THEREAFTER WILL
BEGIN TO DECREASE AS WE MOVE FURTHER AWAY FROM THE FULL MOON AND
PERIGEE. SHALLOW COASTAL FLOODING APPEARS UNLIKELY AFTER SUNDAY.

&&

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

&&

$$

ST



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