322
FXUS62 KCHS 161658
AFDCHS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
1258 PM EDT WED OCT 16 2013
...SHALLOW COASTAL FLOODING LIKELY AGAIN TONIGHT...
...COASTAL FLOOD ADVISORY IN EFFECT FROM 5 PM AND 10 PM TONIGHT...
.SYNOPSIS...
WEAK HIGH PRESSURE WILL PREVAIL OVER THE REGION INTO THURSDAY. A
COLD FRONT WILL MOVE INTO THE AREA THURSDAY NIGHT...THEN WILL STALL
ALONG THE SOUTHEAST COAST THROUGH SATURDAY. THE FRONT WILL PUSH
OFFSHORE ON SUNDAY AS HIGH PRESSURE BUILDS FROM THE NORTHWEST AND
PREVAILS INTO EARLY NEXT WEEK. A WAVE OF LOW PRESSURE MAY APPROACH
FROM THE SOUTHWEST DURING THE MIDDLE OF THE WEEK.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
INCREASED CLOUD COVER A BIT OVER THE CHARLESTON TRI-COUNTY AREA
WHERE LOW CLOUDS ARE HOLDING FIRM. LATEST SATELLITE DATA HOWEVER
SUGGEST THE CLOUDS ARE STARTING TO MIX OUT AND ERODE FROM THE
WEST. NO OTHER CHANGES WERE MADE.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH SATURDAY/...
TONIGHT...CONTINUED RAIN-FREE ALTHOUGH DEEPER MOISTURE WILL
BE IMPINGING ON THE AREA FROM THE WEST AHEAD OF A COLD FRONT
PUSHING TOWARD THE APPALACHIANS. GENERALLY TOOK A COMPROMISE OF
THE MOS GUIDANCE WITH LOWS AROUND 60 INLAND AND MID/UPPER 60S NEAR
THE COAST. LIGHT WINDS AND SUFFICIENT LOW-LEVEL MOISTURE WILL BE
CONDUCIVE TO FOG FORMATION ALTHOUGH HIGHER CLOUDS WILL DETERMINE
THIS POTENTIAL. FOR NOW WE INCLUDED PATCHY FOG ACROSS PORTIONS OF
SOUTHEAST GEORGIA CLOSE TO THE ALTAMAHA RIVER WHICH SHOULD SEE THE
LEAST IMPACT FROM CLOUDS AND A SLIGHTLY INCREASING LOW-LEVEL WIND.
THURSDAY AND THURSDAY NIGHT...A STRONG SHORT WAVE EMBEDDED WITHIN A
BROAD AND MOSTLY CYCLONIC FLOW OVER MUCH OF THE LOWER 48 STATES WILL
LIFT NE THROUGH THE OHIO VALLEY AND GREAT LAKES DURING THE DAYTIME
HOURS...THEN INTO THE NE STATES AFTER NIGHTFALL. AS THIS OCCURS IT
NUDGES THE DEEP RIDGING OVER THE LOCAL REGION INTO THE NEARBY
ATLANTIC. THIS IN TURN ALLOWS FOR A COLD FRONT ORIENTED NE-SW TO
APPROACH FROM THE NW THURSDAY NIGHT...PRECEDED BY A PRE-FRONTAL
TROUGH. THERE IS LITTLE CHANGE IN MID-TROPOSPHERIC HEIGHTS WITHIN
THE ZONAL SW TO WEST FLOW...AND THE BEST DYNAMICS AND JET FORCING
REMAIN OUTSIDE OF THE CWFA. THUS OUR PROGNOSIS IS FOR LITTLE IN THE
WAY OF RAIN IN ASSOCIATION WITH THESE APPROACHING SURFACE FEATURES.
WITH CONDENSATION PRESSURE DEFICITS 100 MILLIBARS OF GREATER ON
THURSDAY WE HAVE OPTED TO KEEP THE FORECAST RAIN-FREE...ALTHOUGH AS
THE PRE-FRONTAL TROUGH SLIDES IN LATE THERE CERTAINLY COULD BE A
COUPLE OF ISOLATED SHOWERS ALONG THE NW TIER AFTER 5 PM. THE
MOISTURE DEPTH INCREASES THURSDAY NIGHT AND LOW LEVEL FORCING WITH
THE PRE-FRONTAL TROUGH AND APPROACHING FRONT WILL SPUR AT LEAST A
SMALL CHANCE OF POPS. WHILE WE DO HAVE DECENT SHEAR...IT IS
GENERALLY UNI-DIRECTIONAL. AND GIVEN POOR LAPSE RATES AND LIMITED
SBCAPES THE RISK FOR THUNDER IS ABSENT FROM THE FORECAST. BUT SINCE
THERE ARE HINTS OF A LITTLE ELEVATED INSTABILITY WITH SHOWALTER
VALUES DOWN AROUND ZERO...IT CAN/T BE ENTIRELY DISCOUNTED THURSDAY
NIGHT.
DESPITE PARTLY TO MOSTLY CLOUDY SKY COVER THURSDAY...THE WARM SW
FLOW AND COMPRESSIONAL HEATING IN ADVANCE OF THE COLD FRONT WILL
ALLOW FOR MAX TEMPS TO CLIMB WELL ABOVE MID OCTOBER NORMS. WITH 850
MILLIBAR TEMPS OF 15-16C WE ARE SHOOTING FOR LOWER AND MIDDLE 80S
AWAY FROM THE BEACHES. THURSDAY NIGHT WILL BE WARM AND HUMID WITH
EXTENSIVE CLOUD COVER AS THE COLD FRONT DRAWS CLOSER. THIS
BLANKETING EFFECT WILL KEEP TEMPS FROM DROPPING ANY LOWER THAN THE
LOWER OR MIDDLE 60S INLAND AND THE UPPER 60S TO NEAR 70 AT THE
COAST.
FRIDAY THROUGH SATURDAY...THE COLD FRONT WILL STALL OUT OVER
SOUTHERN SC AND SE GA AS IT BECOMES PARALLEL TO THE FLOW ALOFT. A
MID LEVEL PERTURBATION WITHIN THE ZONAL WEST AND SW FLOW WILL MOVE
THROUGH LATE FRIDAY AND FRIDAY NIGHT...WHICH WILL TRIGGER THE
FORMATION OF A SURFACE WAVE ON THE FRONT AS IT TREKS NE NEAR OUR
COASTAL ZONES. THE PROXIMITY TO THE FRONT WILL PROVIDE AMPLE
LIFT...AND THERE ARE EVEN INDICATIONS THAT A SEA BREEZE COULD ALSO
DEVELOP ON FRIDAY...PROVIDING ANOTHER MECHANISM FOR FORCING. WE/LL
GO WITH 20-30 POPS THROUGH THE PERIOD...HIGHEST NEAR THE COAST AND
CLOSER TO THE EXPECTED PATH OF THE SURFACE WAVE. SBCAPES ARE
ACTUALLY A LITTLE GREATER THAN ON THURSDAY...BUT GIVEN POOR LAPSE
RATES YET AGAIN WE ARE HESITANT TO ADD THUNDER TO THE FORECAST JUST
YET. TEMPS WILL BE DETERMINED BY WHERE THE FRONT ALIGNS ITSELF...BUT
GIVEN THE LACK OF COOL AIR WE/LL STILL BE ABOVE SEASONAL LEVELS.
&&
.LONG TERM /SATURDAY NIGHT THROUGH TUESDAY/...
IT LOOKS LIKE THE COLD FRONT WILL BE FORCED EAST AND SE INTO THE
ATLANTIC FOR EARLY NEXT WEEK AS HIGH PRESSURE BUILDS EAST OUT OF THE
CENTRAL AND EASTERN PARTS OF THE COUNTRY. BUT THE BAROCLINIC ZONE
WILL BEGIN TO WORK ITS WAY BACK NORTH BY THE MIDDLE OF THE WEEK AS A
SOUTHERN STREAM SHORT WAVE AND ITS CO-LOCATED SURFACE WAVE LIFTS
INTO THE SE PART OF THE COUNTRY. BUT WHEN THIS OCCURS AND EXACTLY
WHERE THE TRACK OF THE SURFACE LOW OCCURS REMAINS TO BE SEEN THIS
FAR IN ADVANCE. RAIN CHANCES WILL DIMINISH LATER SUNDAY INTO
MONDAY...BUT COULD START TO CLIMB AGAIN IN ADVANCE OF THE NEXT
SYSTEM TUESDAY AND/OR WEDNESDAY. ADJUSTMENTS WILL LIKELY BE REQUIRED
IN SUBSEQUENT FORECASTS. TEMPS WILL BE A BIT COOLER INTO EARLY IN
THE WEEK...BUT COULD MODERATE AGAIN BY MID WEEK.
&&
.AVIATION /18Z WEDNESDAY THROUGH MONDAY/...
VFR FOR THE NEXT 24 HOURS. MVFR CIGS AT KCHS WILL LIKELY HOLD ON
THROUGH ABOUT 20-21Z BEFORE BREAKING AS THEY ERODE FROM THE WEST.
LIGHT/SHALLOW GROUND FOG IS POSSIBLE AT EITHER TERMINAL...BUT
ANY SIGNIFICANT IMPACTS SEEM LOW AT THIS POINT.
EXTENDED AVIATION OUTLOOK..MVFR CONDITIONS ARE POSSIBLE AT TIMES
INTO THE WEEKEND AS A FRONT STALLS OVER THE AREA.
&&
.MARINE...
TODAY AND TONIGHT...IMPROVING CONDITIONS BEYOND THIS MORNING WITH
VEERING WINDS MAINLY 10 KT OR LESS AS HIGH PRESSURE SLIDES OVER
THE AREA.
THURSDAY THROUGH MONDAY...WEAK HIGH PRESSURE ATOP THE LOCAL WATERS
THURSDAY WILL GIVE WAY TO AN APPROACHING COLD FRONT FRIDAY THAT
STALLS OUT NEAR THE AREA INTO SATURDAY. THE FRONT WILL SLIDE TO THE
EAST AND SE OF THE MARINE AREA SUNDAY INTO MONDAY...AS CONTINENTAL
HIGH PRESSURE BUILDS OVER THE EAST AND SE STATES AND EVENTUALLY INTO
THE WESTERN ATLANTIC. WINDS THROUGH THE FORECAST PERIOD WILL BE HELD
TO 15 KT OR LESS...AND SEAS NO HIGHER THAN 2 OR 3 FT. THE BEST
CHANCE FOR SHOWERS AND POSSIBLE T-STORMS WILL BE FRIDAY INTO
SUNDAY.
&&
.TIDES/COASTAL FLOODING...
ISSUED ANOTHER COASTAL FLOOD ADVISORY FOR ALL COASTAL ZONES...
INCLUDING TIDAL BERKELEY...VALID 5-10 PM. TIDE IN THE CHARLESTON
HARBOR IS EXPECTED TO PEAK 7.2-7.5 FT MLLW AND 9.1-9.4 FT MLLW
AT FORT PULASKI.
ASTRONOMICAL HIGH TIDES COURTESY OF THE FULL MOON THAT OCCURS FRIDAY
EVENING WILL MOST PROBABLY GENERATE ADDITIONAL SHALLOW COASTAL
FLOODING WITH MOST IF NOT ALL HIGH TIDES INTO THE WEEKEND. AND WITH
AN EXPECTED NE FETCH FOR EARLY NEXT WEEK...THIS COASTAL FLOODING
CONCERN COULD LINGER EVEN LONGER.
&&
.CHS WATCHES/WARNINGS/ADVISORIES...
GA...COASTAL FLOOD ADVISORY FROM 5 PM THIS AFTERNOON TO 10 PM EDT
THIS EVENING FOR GAZ117-119-139-141.
SC...COASTAL FLOOD ADVISORY FROM 5 PM THIS AFTERNOON TO 10 PM EDT
THIS EVENING FOR SCZ048>052.
MARINE...NONE.
&&
$$
ST