Area Forecast Discussion
Issued by NWS Charleston, SC

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000
FXUS62 KCHS 020600
AFDCHS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
100 AM EST MON MAR 2 2015

.SYNOPSIS...
AN INLAND HIGH PRESSURE WEDGE WILL WEAKEN TONIGHT AS A COASTAL
TROUGH LIFTS OFF TO THE NORTHEAST. WEAK HIGH PRESSURE MONDAY WILL
YIELD TO A COLD FRONT AND WEDGE OF HIGH PRESSURE WHICH WILL
ADVANCE INTO THE REGION LATE MONDAY THEN STALL OVER OR JUST SOUTH
OF THE AREA MONDAY NIGHT INTO TUESDAY. THE FRONT WILL LIFT BACK
NORTH AS A WARM FRONT LATE TUESDAY INTO WEDNESDAY. THEN...A COLD
FRONT WILL SHIFT THROUGH THE AREA LATE WEDNESDAY INTO THURSDAY.
COLDER HIGH PRESSURE WILL BUILD OVER THE AREA THROUGH THE WEEKEND.

&&

.NEAR TERM /UNTIL 6 AM THIS MORNING/...
THE FORECAST AREA IS STUCK WITHIN AN EXTREMELY SHALLOW COLD AIR
WEDGE REGIME...WITHIN THE FIRST 800-900 FT PER THE EVENING
SOUNDING...AS A COASTAL TROUGH OFFSHORE PULLS AWAY. THE BULK OF
ANY PRECIP TONIGHT WILL BE IN THE FORM OF DRIZZLE GIVEN WIDESPREAD
LOW CLOUD DECKS AND AN IMPRESSIVE INVERSION JUST OFF THE DECK THAT
HOLDS IN PLACE. LOW STRATUS HAS BUILT DOWN...LOW ENOUGH WHERE
FOG WAS NOW WIDESPREAD. WITH SOME DRIER AIR TO WORK IN FROM THE
WEST/NW WITHIN THE 925-750 MB THIS WILL ALLOW FOR SOME OF THE FOG
TO BECOME DENSE AT TIMES OVERNIGHT. JUST ABOUT ANYWHERE IS FAIR
GAME FOR A DENSE FOG ADVISORY AND RECENTLY AROUND THE CHARLESTON
QUAD-COUNTY REGION...FOG HAD BECOME DENSE. A DENSE FOG ADVISORY
HAS BEEN ISSUED THERE AND IT MAY NEED LATER EXPANSIONS.

DUE TO THE ABSENCE OF ANY COLD OR WARM ADVECTION THERE IS LITTLE
CHANGE IN TEMPS THROUGH THE NIGHT...WITH LOWS TO RANGE FROM 41-42F
NW TIER TO 46-49F ON THE BARRIER ISLANDS.

&&

.SHORT TERM /6 AM THIS MORNING THROUGH 6 PM TUESDAY/...
THIS PERIOD WILL FEATURE A COMPLEX/CHANGEABLE PATTERN. AFTER FOG AND
DRIZZLE TO START MONDAY...THE WEDGE WILL RETREAT...CLOUDS COULD
BREAK FOR SOME SUNSHINE AND TEMPERATURES SHOULD RECOVER INTO THE
LOWER/MID 60S NORTH AND INTO THE UPPER 60S TO LOWER 70S SOUTH.

THEN...A COLD FRONT AND YET ANOTHER WEDGE OF HIGH PRESSURE WILL
ADVANCE INTO THE REGION LATE MONDAY AND MONDAY NIGHT. MEANWHILE...A
WEAK VORT LOBE EMBEDDED WITHIN THE WEAK WEST/NORTHWEST FLOW ALOFT
WILL INTERACT WITH THE FRONT AND ASSOCIATED BAROCLINIC
ZONE/OVERRUNNING REGIME TO PRODUCE ANOTHER ROUND OF LIGHT
RAIN/DRIZZLE...ACCOMPANIED BY LOWERING CEILINGS/SOME
FOG...ESPECIALLY ACROSS NORTHERN COUNTIES LATER MONDAY NIGHT INTO
TUESDAY MORNING. THE SURFACE FRONT WILL EVENTUALLY STALL OVER OR
JUST SOUTH OF SOUTHERN COUNTIES OF THE FORECAST AREA LATER MONDAY
NIGHT INTO TUESDAY MORNING.

AS THE VORT PUSHES EAST AND THE OVERRUNNING SCENARIO WINDS DOWN...
PRECIPITATION COVERAGE SHOULD DECREASE AS TUESDAY PROGRESSES.
ALSO...THE STATIONARY FRONT WILL BEGIN TO LIFT NORTH AS A WARM FRONT
TUESDAY AFTERNOON OR TUESDAY EVENING. THE LATEST FORECAST FOR
TUESDAY HIGH TEMPERATURES VARIES FROM MID/UPPER 50S NORTH TO THE
LOWER/MID 70S SOUTH OF INTERSTATE 16...BUT CONFIDENCE IN THE
POSITION/MAGNITUDE OF THIS TEMPERATURE GRADIENT REMAINS RATHER LOW.

AS THE WARM FRONT CONTINUES TO LIFT NORTH TUESDAY NIGHT...A FEW
SHOWERS COULD OCCUR ESPECIALLY ACROSS NORTHERN/WESTERN
COUNTIES...AND TEMPERATURES SHOULD REMAIN IN THE 50S AND COULD EVEN
RISE ACROSS NORTHERN/WESTERN COUNTIES. CONDITIONS COULD ALSO BECOME
FAVORABLE FOR FOG/STRATUS. MOST SIGNIFICANTLY...THE PROBABILITY FOR
SEA FOG WILL INCREASE AS SOUTHERLY WINDS PUSH DEWPOINTS UPWARD
THROUGH THE 50S OVER THE COOL SHELF WATERS BEGINNING LATE TUESDAY OR
TUESDAY NIGHT.

THE WARM FRONT WILL ADVANCE NORTH OF THE REGION BY WEDNESDAY
MORNING...USHERING AN UNSEASONABLY WARM AIR MASS INTO THE AREA FOR
ONE DAY. AWAY FROM THE COAST...WEDNESDAY TEMPERATURES WILL TOP OUT
IN THE 70S AT MOST LOCATIONS...AND SOME AREAS ACROSS INTERIOR
SOUTHEAST GEORGIA COULD REACH 80F. PRIMARY FORECAST UNCERTAINTY
HINGES ON THE POTENTIAL FOR SEA FOG...THE WIND DIRECTION AND THE
RELATED INLAND PENETRATION OF THE COOL/MOIST MARINE LAYER. SUNDAY
12Z GUIDANCE SUGGESTS THAT SOUTH WINDS COULD PUSH THE MARINE LAYER
ACCOMPANIED BY STRATUS/FOG AND SIGNIFICANTLY COOLER TEMPERATURES IN
THE 50S/60S INTO MOST LOCATIONS EAST OF INTERSTATE 95 ESPECIALLY
WEDNESDAY AFTERNOON. ON THE OTHER HAND...SOUTHWEST WINDS WOULD HOLD
FOG/STRATUS AND COOLER TEMPERATURES ON THE BEACHES/SEA
ISLANDS...ALLOWING FOR GREATER COVERAGE OF TEMPERATURES IN THE
70S/NEAR 80F. THE FORECAST AS OF LATE SUNDAY AFTERNOON INCORPORATES
A COMPROMISE BETWEEN SOUTH/SOUTHWEST WINDS. IN EITHER CASE...LOCALLY
DENSE FOG IS POSSIBLE ALONG THE IMMEDIATE COAST. OTHERWISE...POPS
REMAIN LOW WEDNESDAY...PRIMARILY LIMITED TO SLIGHT CHANCE
NORTHERN/INLAND ESPECIALLY WEDNESDAY AFTERNOON AS THE NEXT COLD
FRONT APPROACHES.

&&

.LONG TERM /TUESDAY NIGHT THROUGH SUNDAY/...
A COLD FRONT WILL APPROACH WESTERN ZONES WEDNESDAY NIGHT WITH MAINLY
SHOWERS. HOWEVER...STRONG FORCING WILL BE ASSOCIATED WITH THE
FRONT...SUPPORTING THE NEED FOR A FEW THUNDERSTORMS OVER INLAND
AREAS EARLY WEDNESDAY NIGHT. THE COLD FRONT WILL THEN CONTINUE TO
PUSH THROUGH THE AREA EARLY THURSDAY...WITH GREATEST COVERAGE OF
SHOWERS THURSDAY MORNING AND AFTERNOON. MOST SHOWERS WILL THEN SHIFT
OFFSHORE THURSDAY NIGHT INTO EARLY FRIDAY AS COOLER HIGH PRESSURE
BUILDS BEHIND THE FRONT. THURSDAY AND FRIDAY NIGHT LOW TEMPS SHOULD
BE THE COOLEST OF THE WEEK. THE LATEST FORECASTS HOLD LOWS IN THE
MID/UPPER 30S BOTH NIGHTS...BUT FREEZING TEMPERATURES CANNOT BE
RULED OUT AWAY FROM THE COAST ESPECIALLY ACROSS NORTHERN/INLAND
COUNTIES. AFTERNOON HIGHS WILL ONLY BE IN THE LOW/MID 50S INTO THE
WEEKEND. HIGH PRESSURE SHOULD PREVAIL THROUGH THE WEEKEND...BUT
THERE ARE INDICATIONS THAT SOME SHOWERS COULD DEVELOP MAINLY ALONG
THE COAST AS A SFC LOW DEVELOPS OFFSHORE AND DEEPENS WHILE LIFTING
TO THE NORTH/NORTHEAST.

&&

.AVIATION /06Z MONDAY THROUGH FRIDAY/...
BOTH KSAV AND KCHS WILL BE STUCK WITHIN IFR OR LOWER CONDITIONS
OVERNIGHT INTO EARLY MONDAY AFTERNOON...WITH A PROMINENT
INVERSION TO LOCK ABUNDANT MOISTURE IN PLACE. WE WILL DROP BELOW
AIRPORT MINIMUMS FOR SEVERAL HOURS DUE TO EXTENSIVE LOW STRATUS
AND/OR FOG...PLUS A LITTLE DRIZZLE AT TIMES. FOR NOW WE HAVEN/T
GONE ANY LOWER THAN 200 FT AND 3/4NM AT KSAV...BUT THAT COULD
CHANGE. FOG WAS DENSE AT 06Z AT KCHS AND WHILE IT MAY BOUNCE
LATER TONIGHT...IT WILL LIKELY TEND TO HANG IN.

SLIGHTLY DRIER AIR WILL ARRIVE FROM THE WEST/NW THIS AFTERNOON
AND AS THE INVERSION LIFTS THERE WILL BE AN IMPROVEMENT BACK INTO
THE MVFR RANGE...PERHAPS EVEN VFR FOR A SHORT TIME. THIS EVENING
AND PRIOR TO 06Z TUESDAY...LOW CLOUDS IN THE WAKE OF A BACKDOOR
COLD FRONT WILL REDEVELOP AROUND KCHS AND MAY IMPINGE ON KSAV
SOMETIME AFTER MID EVENING. LOOK FOR

EXTENDED AVIATION OUTLOOK...FLIGHT RESTRICTIONS MUCH OF THE TIME
THROUGH THURSDAY. POTENTIAL FOR SOME VFR CONDITIONS WEDNESDAY AND
AGAIN FRIDAY.

&&

.MARINE...
OVERNIGHT...A SHARP COASTAL COAST NEAR THE GULF STREAM WILL PULL
FURTHER AWAY FROM THE COAST AND GIVES WAY TO A PORTION OF THE
INLAND WEDGE FROM THE NW BY LATE. THIS WILL RESULT IN NORTHERLY
WINDS OF 15 KT OR LESS THIS EVENING...BACKING AROUND MORE TO THE
NW OVERNIGHT AS SPEEDS DROP TO 10 KT OR UNDER. SEAS WILL STILL BE
ELEVATED GIVEN RECENT STRONG WINDS...AND A SMALL CRAFT ADVISORY
PERSISTS FOR THE OUTER GA WATERS WITH SEAS AS HIGH AS 6 FT.
ELSEWHERE SEAS WILL BE 5 FT OR LOWER IN THE ATLANTIC AND AROUND 1
FOOT WAVES IN CHARLESTON HARBOR. A BIGGER CONCERN WILL BE IN
REGARDS TO FOG POTENTIAL. THE CHARLESTON HARBOR HAS ALREADY BEEN
CLOSED DUE TO DENSE FOG AND A DENSE FOG ADVISORY IS VALID INTO
MONDAY MORNING. ELSEWHERE...LOW STRATUS DECKS UNDER 400-500 FT
WILL LOWER MORE THROUGH THE NIGHT AND THAT WILL GENERATE AREAS OF
FOG THAT BECOMES MORE WIDESPREAD OVERNIGHT. A MARINE DENSE FOG
ADVISORY STILL MAY BE REQUIRED AT A LATER TIME AS VISIBILITIES
WILL LOWER TO 1 NM OR LESS. A MARINE WEATHER STATEMENT IS
PRESENTLY IN EFFECT DUE TO THE FOG FOR THE 0-20 NM WATERS.

MONDAY...A WEAK PRESSURE PATTERN WILL TRANSLATE TO LIGHT WINDS...AND
SEAS WILL REMAIN BELOW SMALL CRAFT ADVISORY LEVELS. MONDAY NIGHT
INTO TUESDAY...A COLD FRONT AND FOLLOWING WEDGE OF HIGH PRESSURE WILL
ADVANCE INTO THE WATERS. THESE FEATURES WILL SUPPORT A SURGE OF
NORTHEAST WINDS...BUT LATEST GUIDANCE SUGGESTS THAT WINDS/SEAS WILL
REMAIN BELOW SCA LEVELS...PERHAPS PEAKING AT NE 15-20 KT ACCOMPANIED
BY SEAS 3-5 FT. THE FRONT WILL THEN STALL SOUTH OF THE WATERS THEN
WILL LIFT NORTH AS A WARM FRONT TUESDAY NIGHT. A WEAKENING PRESSURE
PATTERN WILL THUS SUPPORT SLACKENING WINDS LATER TUESDAY INTO
TUESDAY EVENING...FOLLOWED BY INCREASING SOUTH WINDS LATER TUESDAY
NIGHT INTO WEDNESDAY. ANY SCA CONDITIONS SHOULD REMAIN CONFINED TO
GA WATERS BEYOND 40 NM WEDNESDAY.

ALSO OF NOTE...AS DEWPOINTS CLIMB THROUGH THE 50S AND EVEN INTO THE
LOWER 60S OVER CHILLY SHELF WATERS...THE PROBABILITY FOR AT LEAST
LOCALLY DENSE SEA FOG WILL INCREASE TUESDAY NIGHT THROUGH WEDNESDAY.

WEDNESDAY NIGHT THROUGH SATURDAY...SEA FOG COULD PERSIST INTO
THURSDAY AS MOISTURE PERSIST IN THE WAKE OF A COLD FRONT.
ALSO...WINDS AND SEAS WILL RAMP UP IN THE WAKE OF THE NEXT COLD
FROPA BEGINNING WEDNESDAY NIGHT. SMALL CRAFT ADVISORIES APPEAR
LIKELY BEGINNING AS EARLY AS WEDNESDAY NIGHT OR THURSDAY CONTINUING
INTO THE WEEKEND AS THE GRADIENT TIGHTENS BETWEEN COLDER HIGH
PRESSURE BUILDING INLAND AND A STATIONARY FRONT SOUTH/EAST OF THE
WATERS.

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
SC...DENSE FOG ADVISORY UNTIL 10 AM EST THIS MORNING FOR SCZ043>045-
     049-050-052.
MARINE...SMALL CRAFT ADVISORY UNTIL 5 AM EST EARLY THIS MORNING FOR
     AMZ374.
     DENSE FOG ADVISORY UNTIL 11 AM EST TUESDAY FOR AMZ330.

&&

$$
SYNOPSIS...
NEAR TERM...
SHORT TERM...SPR
LONG TERM...DPB/SPR
AVIATION...
MARINE...



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