Area Forecast Discussion
Issued by NWS Charleston, SC

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000
FXUS62 KCHS 040314
AFDCHS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
1014 PM EST TUE MAR 3 2015

.SYNOPSIS...
A WARM FRONT WILL CONTINUE TO LIFT NORTH OF THE AREA OVERNIGHT.
HIGH PRESSURE WILL REMAIN CENTERED OVER THE ATLANTIC
WEDNESDAY...WHILE A COLD FRONT APPROACHES FROM THE NORTHWEST AND
PASSES THROUGH THE REGION THURSDAY. COLDER HIGH PRESSURE WILL
BUILD OVER THE AREA INTO EARLY SATURDAY...WITH A COASTAL TROUGH TO
DEVELOP OFFSHORE INTO SUNDAY. ANOTHER STORM SYSTEM COULD IMPACT
THE AREA EARLY NEXT WEEK.

&&

.NEAR TERM /UNTIL 6 AM WEDNESDAY MORNING/...
THE WARM FRONT WILL CLEAR THE SANTEE RIVER BY 06Z AND IN IT/S WAKE
A WARM AND EXTREMELY MOIST AIR MASS WILL OVERSPREAD THE ENTIRE
FORECAST DISTRICT ON A DEEP SOUTHERLY FLOW. TEMPS MAY DROP A
COUPLE MORE DEGREES EARLY ON...BUT TEMPS WILL LEVEL OFF OR EVEN
INCREASE OVERNIGHT AS THIS TRANSPIRES. THERE WILL ALSO STILL BE A
FEW LINGERING SHOWERS OVER THE EXTREME SW PART OF CWFA...BUT THESE
WILL END BY MIDNIGHT.

THE MAIN STORY FOR TONIGHT IS IN REGARDS TO FOG...ORIGINATING FROM
BOTH THE LAND AND THE SEA...AND THE BUILD DOWN OF STRATUS. RECENT
OBSERVATIONS...WEB CAMS AND REPORTS FROM THE SAVANNAH PILOT OFFICE
INDICATING THAT SEA FOG FORMED RATHER QUICKLY LATE TUESDAY
EVENING. THIS COVERAGE OF FOG WILL CONTINUE TO FAN OUT AS IT
SPREADS NORTH/NW OVER LAND...MERGES WITH ALREADY PRE-EXISTING LOW
STRATUS AND RADIATION FOG. THEREFORE WE WENT AHEAD WITH A DENSE
FOG ADVISORY FOR LOCATIONS MAINLY NEAR AND EAST OF I-95...ALTHOUGH
THE START TIME OF THE ONE FOR THE CHARLESTON TRI-COUNTY AREA OF 4
AM MIGHT NEED TO BE STARTED SOONER. VISIBILITIES IN THE FOG WILL
BE DOWN NEAR 1/4 MIL OR LESS...EVEN LOCALLY NEAR ZERO. WE STILL
MAY REQUIRE A DENSE FOG ADVISORY FURTHER WEST...ALTHOUGH A 30-40
KT LOW LEVEL JET LOOKS TO BE THE MAIN NEGATING FACTOR...SINCE SEA
FOG SHOULDN/T GET THAT FAR INLAND. THUS THE FOG IN THOSE SECTIONS
WOULD NEED TO BE RADIATION FOG AND STRATUS BUILD-DOWN...AND WITH
WINDS THAT HIGH THERE IS MORE OF A RISK FOR STRATUS RATHER THAN
LAND BASED FOG. WE WILL CONTINUE TO MONITOR NEVERTHELESS.

&&

.SHORT TERM /6 AM WEDNESDAY MORNING THROUGH FRIDAY/...
THE AREA WILL BE IN THE WARM SECTOR AHEAD OF A COLD FRONT WHICH IS
EXPECTED TO PUSH THROUGH THURSDAY AFTERNOON/EVENING. UNSEASONABLY
WARM AND HUMID AIR WILL ADVECT IN FROM THE SOUTH WEDNESDAY INTO
THURSDAY AND THIS WILL BOOST TEMPS TO NEAR 80 INLAND BOTH DAYS.
RECORD HIGHS IN THE LOWER TO MID 80S LOOK TO BE SAFE HOWEVER.
COASTAL AREAS WILL BE MUCH COOLER...PROBABLY STAYING IN THE 60S...
GIVEN THE ONSHORE WINDS...LOW CLOUDS AND SEA FOG WHICH WILL BE
PUSHING ONSHORE FROM TIME TO TIME. COULD SEE A FEW SHOWERS WEDNESDAY
INLAND AND MAINLY NEAR THE SC COAST WED NIGHT BUT THE BEST RAIN
CHANCES WILL COME THURSDAY AS THE FRONT NEARS. COULD EVEN SEE A FEW
THUNDERSTORMS GIVEN THE LIMITED INSTABILITY AND DECENT LOW-LEVEL
JET. MUCH COLDER AIR WILL MOVE IN THURSDAY NIGHT WITH TEMPERATURES
DOWN NEAR FREEZING AT LEAST OVER NORTHERN PORTIONS OF BERKELEY
COUNTY BY DAYBREAK FRIDAY BUT THE PRECIPITATION SHOULD BE MOSTLY
OFFSHORE BY THEN. NOT MUCH WARMUP EXPECTED FRIDAY /HIGHS ONLY IN THE
40S...ABOUT 35-40 DEGREES COLDER COMPARED TO THURSDAY/ AS MOISTURE
HANGS ON THE UPPER FLOW REMAINS MORE SOUTHWEST. WE TRENDED A BIT
WETTER WITH SOME HIGHER RAIN CHANCES...ESPECIALLY NEAR THE COAST.
INTERESTINGLY...SURFACE WET BULB TEMPS ARE PROGGED BY THE NAM/GFS TO
BE NEAR OR JUST BELOW FREEZING OVER INTERIOR PORTIONS OF SOUTHEAST
SC SO WILL HAVE TO WATCH THIS CAREFULLY OVER THE NEXT FEW DAYS FOR
THE POTENTIAL OF AT LEAST SOME FREEZING DRIZZLE.

&&

.LONG TERM /FRIDAY NIGHT THROUGH TUESDAY/...
THERE IS QUITE A BIT OF UNCERTAINTY IN THE LONG TERM PERIOD AS THERE
ARE SIGNIFICANT DIFFERENCES BETWEEN MODEL SOLUTIONS. THE GENERAL
SURFACE PATTERN WILL FEATURE HIGH PRESSURE CENTERED INLAND WHILE A
COASTAL TROUGH DEVELOPS OFFSHORE. THE TROUGH MAY CLOSE OFF INTO A
LOW BEFORE LIFTING NORTHEAST OF THE AREA LATE IN THE WEEKEND.
GENERALLY TEMPERATURES WILL BE COOLER THAN NORMAL INTO EARLY NEXT
WEEK...WITH SLIGHT CHANCE/CHANCE OF RAIN. ANOTHER STORM SYSTEM
COULD IMPACT THE AREA FROM THE SOUTHWEST EARLY NEXT WEEK.

&&

.AVIATION /03Z WEDNESDAY THROUGH SUNDAY/...
WHILE OUR TIMING MAY BE OFF BY A FEW HOURS...WE ARE CONFIDENT
THAT BOTH AIRFIELDS WILL BE IFR OR LOWER THROUGH 15Z WEDNESDAY.
AIRPORT MINIMUMS ARE A DEFINITE POSSIBILITY.

LIGHT WINDS EAST WINDS THIS EVENING WILL BECOME SOUTH TONIGHT.
WITH THE PASSAGE OF A LOW LEVEL JET WE HAVE INCLUDED LOW LEVEL
WIND SHEAR AT KCHS...WHICH MAY ALSO EVENTUALLY BE REQUIRED AT
KSAV. SURFACE WINDS THEN INCREASE BY MID-LATE MORNING WEDNESDAY
WITH DEEP MIXING WITHIN AN UNSEASONABLY WARM AIR MASS. SOUTH/SW
WINDS AIDED BY THE SEA BREEZE WILL PEAK AT 20-25 KT WEDNESDAY
AFTERNOON...EVEN PERIODICALLY HIGHER.

EXTENDED AVIATION OUTLOOK...FLIGHT RESTRICTIONS LIKELY MUCH OF THE
TIME INTO THURSDAY NIGHT...ESPECIALLY AT KCHS...DUE TO LOW CLOUDS
AND FOG/SEA FOG. ALSO EXPECT BREEZY/GUSTY CONDITIONS THURSDAY INTO
FRIDAY.

&&

.MARINE...
TONIGHT...BEHIND THE NORTHWARD PROGRESSING WARM FRONT THE COASTAL
WATERS WILL BE SITUATED ON THE WESTERN EDGE OF THE SUB-TROPICAL
ATLANTIC RIDGE. SOUTHERLY WINDS WILL HOLD AT 15 KT OR LESS AND
SEAS WILL REMAIN AT 4 FT OR LESS.

THE MAIN FORECAST ISSUE WILL CONTINUE TO BE THE DEVELOPMENT AND
EXTENT OF SEA FOG. LATEST SATELLITE IMAGES...WEB CAMS AND COASTAL
OBSERVATIONS INDICATE THAT THE FOG WILL CONTINUE TO RAPIDLY
DEVELOP NOW THAT WINDS ARE VEERING TO THE SOUTH. THIS FAVORABLE
FETCH WILL ADVECT WARM/VERY MOIST AIR ATOP THE CHILLY SHELF WATERS
WHICH WILL PROMOTE AN EXPANSION NORTHWARD OF SEA FOG. AS A RESULT
WE HAVE RAISED A DENSE FOG ADVISORY FOR ALL COASTAL WATERS WITH
THE EXCEPTION OF AMZ374. THE PORTS OF CHARLESTON AND SAVANNAH
WILL LIKELY BECOME CLOSED TO NAVIGATION OVERNIGHT INTO WEDNESDAY
MORNING. VISIBILITIES WILL LOWER TO 1/2 NM OR LESS...EVEN DOWN
NEAR ZERO AT TIMES.

WEDNESDAY THROUGH SATURDAY...SURFACE HIGH PRESSURE WILL BE CENTERED
EAST OF THE WATERS WEDNESDAY INTO THURSDAY AHEAD OF AN APPROACHING
COLD FRONT. WINDS AND SEAS WILL PICK UP...MAINLY NEAR THE COAST AND
OVER THE OUTER WATERS WHERE THE BEST MIXING IS EXPECTED WITH
ADVISORIES POSSIBLE WED NIGHT OVER THE OUTER GA WATERS. GIVEN WARM
MOIST AIRMASS MOVING OVER THE COOLER ...SEA FOG WILL LIKELY DEVELOP.
VISIBILITIES MAY DROP TO 1/2 NM OR LESS AND DENSE FOG ADVISORIES MAY
EVENTUALLY BE NEEDED...ESPECIALLY OVER THE COOLER NEAR SHORE WATERS.
THE COLD FRONT WILL PUSH THROUGH THE WATERS THURSDAY EVENING WITH
WINDS/SEAS INCREASING. SMALL CRAFT ADVISORIES WILL BE POSSIBLE FOR
MOST MARINE LEGS THURSDAY AFTERNOON INTO AT LEAST FRIDAY NIGHT
BEFORE THE PRESSURE GRADIENT RELAXES.

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...DENSE FOG ADVISORY UNTIL NOON EST WEDNESDAY FOR GAZ116>119-
     138>141.
SC...DENSE FOG ADVISORY UNTIL NOON EST WEDNESDAY FOR SCZ047-048-051.
     DENSE FOG ADVISORY FROM 4 AM TO NOON EST WEDNESDAY FOR
     SCZ043>045-049-050-052.
MARINE...DENSE FOG ADVISORY UNTIL 2 PM EST WEDNESDAY FOR AMZ352-354.
     DENSE FOG ADVISORY FROM 4 AM TO 2 PM EST WEDNESDAY FOR AMZ350.
     DENSE FOG ADVISORY FROM 4 AM TO NOON EST WEDNESDAY FOR AMZ330.

&&

$$
SYNOPSIS...
NEAR TERM...BSH
SHORT TERM...RJB
LONG TERM...ECT
AVIATION...
MARINE...



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