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AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
611 AM EST SUN DEC 28 2014

.SYNOPSIS...
HIGH PRESSURE WILL PULL FURTHER OFFSHORE TODAY. A COLD FRONT WILL
SLOWLY MOVE THROUGH THE REGION LATE MONDAY AND MONDAY NIGHT. HIGH
PRESSURE WILL THEN BUILD INTO THE AREA TUESDAY THROUGH THURSDAY...
BEFORE MOVING INTO THE ATLANTIC LATE IN THE WEEK. A COLD FRONT
COULD APPROACH NEXT WEEKEND.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
HIGH PRESSURE CENTERED WELL OFFSHORE OF THE NORTH CAROLINA OUTER
BANKS WILL SHIFT FARTHER OUT INTO THE ATLANTIC TODAY AS A COLD
FRONT APPROACHES FROM THE WEST. A VERY WEAK COASTAL TROUGH NOTED
OVER THE GULF STREAM YESTERDAY EVENING HAS DISSIPATED WITH THE
LOW-LEVEL WIND FIELD OVER THE LOCAL MARINE AREA NOW SOUTHWEST
VERSUS NORTHEAST. THE EXPANSIVE UPPER RIDGE THAT IS IN PLACE ALOFT
WILL NUDGE EAST TODAY A POTENT SHORTWAVE OVER THE SOUTHERN
ROCKIES/ 4-CORNERS REGION DIGS INTO NORTHERN MEXICO AND THE
EDWARDS PLATEAU OF TEXAS. THERE LOOKS TO BE ENOUGH RIDING BOTH AT
THE SURFACE AND ALOFT TO KEEP THE PRIMARY MOISTURE CONVEYOR AHEAD
OF THE COLD FRONT TO THE WEST TODAY...THUS KEEPING DRY CONDITIONS
IN PLACE FOR ALL OF SOUTHEAST SOUTH CAROLINA AND SOUTHEAST
GEORGIA. IT WILL BE WARM DAY AS 850 HPA TEMPERATURES RISE TO +12C
TO +14C... ALTHOUGH MID/HIGH LEVEL CLOUDINESS WILL TEMPER THE
WARMTH POTENTIAL SOMEWHAT. IT WILL STILL BE A VERY WARM DAY FOR
LATE DECEMBER WITH HIGHS RISING INTO THE MID 70S AWAY FROM THE
BEACHES. A FEW UPPER 70S WILL BE POSSIBLE FOR AREAS CLOSEST TO THE
ALTAMAHA RIVER AS MORE BREAKS IN THE CLOUD COVER ARE EXPECTED TO
OCCUR THERE. IMMEDIATE BEACH LOCATIONS WILL LIKELY STRUGGLE TO
REACH THE LOWER 60S DUE TO THE PROXIMITY OF CHILLY ATLANTIC SHELF
WATERS IN THE MID 50S AND POSSIBLY SEA FOG.

THERE IS A POTENTIAL FOR SIGNIFICANT SEA FOG DEVELOPMENT OVER THE
COASTAL WATERS TODAY AS WARM/MOIST AIR BEGINS TO FLOW OVER THE
CHILLY SHELF WATERS THAT ARE IN PLACE OFF THE COAST. THE SYNOPTIC
MODELS HAVE BEEN HINTING AT SEA FOG DEVELOPMENT FOR QUITE SOME
TIME...ALTHOUGH ITS ONSET AND EXTENT IS STILL IN QUESTION. 
CONDITIONS CERTAINLY LOOK RIPE FOR WIDESPREAD SEA FOG DEVELOPMENT...
SIMILAR TO WHAT HAS BEEN SEEN OVER THE PAST SEVERAL WEEKS DURING
WARM PERIODS. ANY SEA FOG THAT FORMS OFFSHORE COULD CERTAINLY
BEGIN TO MOVE INLAND THIS AFTERNOON AS A SEA BREEZE CIRCULATION
TAKES HOLD ALONG THE COAST. DEPENDING ON HOW STRONG THE THERMALLY
DIRECT CIRCULATION BECOMES...DENSE FOG COULD BE ADVECTED AS FAR
INLAND AS THE INTRACOASTAL WATERWAY...CHARLESTON HARBOR AND
POSSIBLY THE SAVANNAH RIVER...AFFECTING DOWNTOWN CHARLESTON AND
PARTS OF DOWNTOWN SAVANNAH BY LATE AFTERNOON.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH WEDNESDAY/...
TONIGHT...MEAN RIDGING WILL LIKELY GIVE WAY ENOUGH OVERNIGHT THAT
ISOLATED TO PERHAPS LOW-END SCATTERED SHOWERS COULD IMPACT MAINLY
THE CENTRAL AND WESTERN PORTIONS OF THE FORECAST AREA LATE TONIGHT
AS A COLD FRONT AND WEAK FRONTAL WAVE APPROACHES. RAINFALL
AMOUNTS...IF ANY...WILL BE LIGHT AS MODELS STILL DEPICT A WELL-
DEFINED MID-LEVEL CLOUD POCKET HOLDING FIRM. WILL HIGHLIGHT 20-30
PERCENT POPS IN THESE AREAS...ALTHOUGH CONFIDENCE FOR ACTUALLY
SEEING MEASURABLE RAINFALL IS LOW. IT WILL BE ANOTHER WARM NIGHT
WITH LOWS RANGING FROM THE UPPER 50S INLAND TO THE LOWER 60S
COAST.

OUR BIGGEST CONCERN TONIGHT IS FOR THE POTENTIAL FOR A WIDESPREAD
DENSE SEA FOG EVENT UNFOLDING ACROSS THE AREA. AREAS OF SEA FOG
WILL LIKELY BE ONGOING ACROSS THE COASTAL WATERS AND POSSIBLY THE
COASTAL COUNTIES AT SUNSET...WHICH SHOULD SPREAD INLAND UNDERNEATH
THE NOCTURNAL INVERSION AS THE NIGHT PROGRESSES. IN ADDITION...
MODELS SUGGEST A SECONDARY AREA OF SEA FOG AND RADIATION FOG WILL
DEVELOP OVER THE NORTHEAST GULF AND FLORIDA PANHANDLE THIS
EVENING...THEN GRADUALLY SPREAD IN FROM THE SOUTH AND SOUTHWEST
AFTER MIDNIGHT. CONDITIONS CERTAINLY LOOK FAVORABLE FOR WIDESPREAD
FOG TO AFFECT MANY AREAS TONIGHT...BUT FORECASTING THE TIMING AND
EXTENT OF SEA FOG IS ALWAYS A CHALLENGE. CONFIDENCE IN SEA FOG
FORMING IS RATHER HIGH GIVEN EXTENSIVE SEA FOG HAS ALREADY
OCCURRED DURING PREVIOUS WARM SPELLS EXPERIENCED OVER THE PAST FEW
WEEKS...BUT IT REMAINS TO BE SEEN EXACTLY HOW THIS EVENT WILL PLAY
OUT. WILL HIGHLIGHT AREAS OF FOG AND WIDESPREAD FOG ALL AREAS
TONIGHT...GRADUALLY SPREADING INLAND AND FROM THE SOUTH OVERNIGHT.
THE INTRODUCTION OF DENSE AND VISIBILITY ATTRIBUTES MAY EVENTUALLY
BE NEEDED IN THE GRIDDED AND TEXT FORECASTS. A DENSE FOG ADVISORY
MAY VERY WELL BE NEEDED FOR SOME AREAS OVERNIGHT AND THIS
POTENTIAL WILL REMAIN HIGHLIGHTED IN THE HAZARDOUS WEATHER
OUTLOOK.

MONDAY...WEAKENING SHORTWAVE ENERGY WILL MOVE ACROSS THE MID
ATLANTIC AND CAROLINA COASTLINE DURING THE MORNING AND AFTERNOON
TIME FRAME. A COLD FRONT WILL SHIFT INTO THE FORECAST AREA AND
GRADUALLY SLIP OFF THE SOUTHEAST COAST THROUGH THE EVENING AND
OVERNIGHT. ALTHOUGH THE BEST CHANCE OF RAIN DURING THE SHORT TERM
PERIOD APPEARS TO OCCUR WITH FRONTAL PASSAGE MONDAY AFTERNOON...
PREFER TO CAP POPS BELOW THE LIKELY CATEGORY CONSIDERING SOME
UNCERTAINTIES REGARDING COVERAGE. WILL INDICATE RAIN CHANCES
PEAKING IN THE 40 PERCENT RANGE TO ACCOUNT FOR SOME FRONTAL
CONVERGENCE AND MOISTURE ACCESS...WHILE STILL REMAINING
CONSERVATIVE SINCE THE FRONT WILL BE NEARLY PARALLEL TO THE
DAMPENING FLOW ALOFT AND SHORTWAVE ENERGY WILL BE IN A WEAKENING
STATE. COMPRESSIONAL WARMING IN ADVANCE OF THE COLD
FRONT...COMBINED WITH A DOWNSLOPE FLOW COMPONENT...WILL SUPPORT
ANOTHER UNSEASONABLY WARM DAY. EXPECT TEMPERATURES TO PEAK IN THE
UPPER 60S TO LOW 70S...WHILE LOW TEMPERATURES ARE RELATIVELY MILD
IN THE LOW TO MID 50S.

TUESDAY...RAIN WILL STEADILY DIMINISH IN COVERAGE FROM NORTHWEST
TO SOUTHEAST THROUGH THE MORNING HOURS...AS THE COLD FRONT AND AN
ASSOCIATED WAVE OF LOW PRESSURE MOVE FARTHER AWAY FROM THE COAST.
RAIN CHANCES WILL FALL BELOW 15 PERCENT BY EARLY AFTERNOON...WITH
SKY COVER SLOWLY SCATTERING TOWARD THE EVENING HOURS. COLD
ADVECTION AND NORTH FLOW IN THE WAKE OF THE FRONT AND ALONG THE
PERIPHERY OF EXPANSIVE HIGH PRESSURE BUILDING FROM THE WEST WILL
SUPPORT COOLER AND DRIER CONDITIONS. HIGH TEMPERATURES WILL RANGE
FROM THE LOW 60S NORTH TO THE MID 60S SOUTH...WITH NIGHTTIME LOWS
FALLING INTO THE UPPER 30S TO LOWER 40S.

WEDNESDAY...AN IMPRESSIVELY STRONG AND EXPANSIVE SURFACE HIGH WILL
STRETCH ACROSS MUCH OF THE CENTRAL AND EASTERN UNITED STATES BY
MID WEEK. EXPECT RATHER QUIET CONDITIONS TO PREVAIL...WITH
TEMPERATURES A DEGREE OR TWO BELOW SEASONAL NORMALS. HIGH
TEMPERATURES WILL BE IN THE LOW 50S NORTH TO UPPER 50S SOUTH UNDER
MOSTLY CLEAR SKIES.

&&

.LONG TERM /WEDNESDAY NIGHT THROUGH SATURDAY/...
THE EXPANSIVE SURFACE HIGH WILL STEADILY SHIFT OVER THE SOUTHERN
UNITED STATES BY THURSDAY...BEFORE SHIFTING INTO THE ATLANTIC
WATERS FRIDAY AND SATURDAY. A STRONG CUT OFF LOW OVER SOUTHERN
CALIFORNIA THURSDAY MORNING WILL WEAKEN WHILE TRACKING ACROSS THE
SOUTHWEST STATES FRIDAY...EVENTUALLY PROVIDING THE NECESSARY
ENERGY TO SPIN UP A SURFACE LOW PRESSURE SYSTEM THAT WILL LIFT
INTO THE OHIO VALLEY SATURDAY. THE TRAILING COLD FRONT FROM THIS
SYSTEM WILL CROSS THE EASTERN UNITED STATES OVER THE WEEKEND. WILL
MAINTAIN DRY WEATHER WEDNESDAY NIGHT THROUGH THURSDAY AS HIGH
PRESSURE REMAINS IN CONTROL...THEN REINTRODUCE RAIN CHANCES FRIDAY
INTO THE WEEKEND TO ACCOUNT FOR THE NEXT FRONTAL SYSTEM. LATEST
MODEL SOLUTIONS SUGGEST BEST RAIN POTENTIAL WILL BE
SATURDAY...WHEN THE COLD FRONT IS CURRENTLY FORECAST TO BE
CROSSING THE REGION. WILL ADVERTISE SEASONAL TEMPERATURES THURSDAY
AND FRIDAY...THEN INDICATE A WARMING TREND FRIDAY NIGHT INTO THE
WEEKEND AHEAD OF THE APPROACHING FRONT.

&&

.AVIATION /11Z SUNDAY THROUGH THURSDAY/...
VFR TODAY ATHOUGH THERE IS A SLIGHT CHANCE FOR A BRIEF PERIOD OF
MVFR CIGS AT BOTH KCHS/KSAV JUST AFTER SUNSET IF THE RAP SOUNDINGS
PROVE CORRECT. SEA FOG IS EXPECTED TO DEVELOP OFF THE COAST LATER
TODAY. SOME OF THIS WILL SPREAD INLAND LATE THIS AFTERNOON WITH
THE SEA BREEZE WITH A BIGGER PUSH EXPECTED OVERNIGHT. AT THIS
TIME...THE BEST CHANCES FOR SIGNIFICANT IMPACTS LOOKS TO BE AT
KCHS...ALTHOUGH PROBABILITIES ARE HIGH AT KSAV AS WELL. WILL TAKE
A SOMEWHAT CONSERATIVE APPROACH WITH THE 12Z TAFS SINCE THE TIMING
AND EXTENT IS STILL A BIT UNCERTAIN. WILL SHOW MVFR VSBYS/CIGS THIS
EVENING...DROPPING TO LIFR AT KCHS BY 06Z WITH HIGH-END IFR AT
KSAV. BOTH SITES COULD VERY WELL DROP BELOW AIRFIELD MINIMUMS
AFTER 06Z...BUT WILL NOT INTRODUCE THOSE CONDITIONS JUST YET.

EXTENDED AVIATION OUTLOOK...FLIGHT RESTRICTIONS LIKELY LATE
MONDAY INTO MONDAY NIGHT AS A COLD FRONT MOVES ACROSS THE REGION.

&&

.MARINE...
TODAY...VARIABLE WINDS WILL GRADUALLY BECOME SOUTH TO SOUTHWEST
TODAY AS A COLD FRONT APPROACHES FROM THE WEST. WINDS WILL REMAIN
LESS THAN 10 KT THROUGH THE DAY ONCE THE WIND PICKS UP. THERE WILL
BE A RISK FOR SEA FOG DEVELOPING TODAY AS WARM/MOIST AIR FLOWS
OVER THE CHILLY SHELF WATERS. THE ONSET AND EXTENT OF THE SEA FOG
REMAINS IN QUESTIONS...ALTHOUGH MODELS HAVE BEEN HINTING AT THIS
FOR SEVERAL RUNS NOW...ESPECIALLY OVER THE GEORGIA AND BEAUFORT
COUNTY WATERS WHERE AIR PARCEL RESIDENCE TIMES WILL BE THE
LONGEST. WILL LIMIT CONDITIONS TO AREAS OF FOG FOR NOW...ALTHOUGH
THE FOG MAY VERY WELL BECOME WIDESPREAD AND DENSE. A MARINE DENSE
FOG ADVISORY MAY EVENTUALLY BE NEEDED AND WILL BE ADDRESSED IN THE
HAZARDOUS WEATHER OUTLOOK. SEAS WILL AVERAGE 2 FT NEARSHORE AND
3-4 FT OFFSHORE...MAINLY IN LONG PERIOD EAST SWELLS WITH PERIODS
OF 15-18 SECONDS.

TONIGHT...CONDITIONS LOOK TO FAVOR WIDESPREAD DENSE SEA FOG ACROSS
THE NEARSHORE WATERS AS SOUTHWEST WINDS DOMINATE WITH SPEEDS LESS
THAN 10 KT. IT IS STILL UNCLEAR EXACTLY HOW WIDESPREAD AND DENSE
THE SEA FOG WILL BECOME...BUT CONFIDENCE IS INCREASING THAT A
NASTY DENSE SEA FOG EVENT WILL OCCUR. WILL GO AHEAD AND INTRODUCE
WIDESPREAD FOG IN THE GRIDDED AND TEXT FORECASTS...BUT NO
INTRODUCE DENSE WORDING JUST YET. SEAS WILL AVERAGE 2-3 FT
NEARSHORE WATERS AND 3-4 FT OFFSHORE WATERS...MAINLY IN LONG
PERIOD EAST SWELL.

MONDAY...A COLD FRONT WILL SLIP INTO THE COASTAL WATERS DURING
THE EVENING/OVERNIGHT HOURS...ALLOWING SOUTHWEST FLOW EARLY IN THE
DAY TO VEER NORTH OVER THE SOUTH CAROLINA WATERS AND NORTHWEST
ACROSS GEORGIA MARINE ZONES. SEA FOG WILL PERSIST ACROSS THE
NEARSHORE WATERS DURING THIS TIME...MOST LIKELY JUST OUTSIDE OF
CHARLESTON AND SAVANNAH HARBORS. HOWEVER...IF WINDS BACK MORE TO
THE SOUTH DURING THE DAYTIME PERIOD...FOG COULD IMPACT ONE OR BOTH
OF THESE PORTS.

TUESDAY THROUGH THURSDAY...AN IMPRESSIVE AREA OF HIGH PRESSURE
WILL BUILD ACROSS THE CENTRAL AND EASTERN UNITED STATES EARLY IN
THE WEEK...EVENTUALLY SETTLING OVER THE SOUTHEAST COAST BY
THURSDAY. THE PRESSURE GRADIENT WILL TIGHTEN ON THE PERIPHERY OF
THE BUILDING SURFACE HIGH...AND CONSIDERING SOME COLD ADVECTION IN
THE WAKE OF THE DEPARTING COLD FRONT...MARGINAL SMALL CRAFT ADVISORY
CONDITIONS ARE POSSIBLE FOR PORTIONS OF THE WATERS TUESDAY INTO
EARLY WEDNESDAY. AS THE CENTER OF THE HIGH SHIFTS TOWARD THE
SOUTHEAST STATES THURSDAY...THE PRESSURE GRADIENT WILL WEAKEN
SUFFICIENTLY TO ALLOW WINDS/SEAS TO SUBSIDE.

&&

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

&&

$$

ST


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