Area Forecast Discussion
Issued by NWS Charleston, SC

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000
FXUS62 KCHS 271055
AFDCHS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
547 AM EST SAT DEC 27 2014

.SYNOPSIS...
HIGH PRESSURE WILL SHIFT OFF THE COAST THROUGH TONIGHT. A COLD
FRONT WILL MOVE THROUGH THE REGION LATE MONDAY OR MONDAY NIGHT.
HIGH PRESSURE WILL BUILD INTO THE AREA FOR MUCH OF NEXT WEEK. A
STORM SYSTEM COULD APPROACH OVER THE WEEKEND.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
HIGH PRESSURE CENTERED OVER THE NORTH CAROLINA CENTRAL COASTAL AREA
AND OUTER BANKS WILL SHIFT OFFSHORE TODAY AS A COLD FRONT APPROACHES
FROM THE WEST. A WEAK COASTAL TROUGH NOTED WELL OFFSHORE WILL REMAIN
WEAK WITH LITTLE DIRECT IMPACT ON THE FORECAST AREA. SOME
STRATOCUMULUS ASSOCIATED WITH SOME SUBTLE ISENTROPIC 295K ASSENT
ATOP THE TROUGH COULD BRUSH THE MAINLY THE SOUTH CAROLINA COASTAL
AREAS THROUGH THE DAY...BUT DRY CONDITIONS WILL PERSIST. IT WILL BE
A WARM DAY WITH AFTERNOON HIGHS RISING INTO THE UPPER 60S FOR MOST
LOCATIONS AWAY FROM THE IMMEDIATE COAST. A SUBTLE SEA BREEZE
CIRCULATION WILL LIKELY DEVELOP ALONG THE BEACHES BY MID-
AFTERNOON...BUT HIGH RESOLUTION MODELS SUGGEST THE DIRECT
CIRCULATION WILL REMAIN WEAK AT BEST. HIGH CLOUDS WILL BEGIN TO
INCREASE FROM THE SOUTHWEST LATER TODAY AS THE EXPANSIVE UPPER RIDGE
MOVES SLOWLY EAST IN RESPONSE TO A DEEPENING UPPER TROUGH OVER THE
SOUTHERN ROCKIES AND FOUR CORNERS REGION.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH TUESDAY/...
TONIGHT...QUIET CONDITIONS WILL PERSIST. THE 27/00Z NAM IS STILL
LIKELY OVERPLAYING THE STRENGTH OF THE COASTAL TROUGH OFFSHORE AND
ACTUALLY TRIES TO PINCH OFF A WEAK MESOLOW OFF THE CHARLESTON
COUNTY COAST AFTER MIDNIGHT. THIS SCENARIO LOOKS UNREALISTIC WITH
THE CENTER OF THE SURFACE HIGH FORECAST TO BE WELL OFFSHORE OF THE
NORTH CAROLINA COAST BY SUNRISE SUNDAY. WE CONTINUE TO PREFER THE
27/00Z GFS/ECMWF/GEM SOLUTIONS WHICH SHOW THE COASTAL TROUGH
WASHING OUT IN THE STRENGTHENING SOUTHERLY FLOW AHEAD OF AN
APPROACHING COLD FRONT. STILL CAN NOT RULE OUT A FEW SHOWERS
DEVELOPING OVER THE CHARLESTON COUNTY WATERS AND POSSIBLY THE
GEORGIA OFFSHORE WATERS LATE...BUT THESE SHOULD LARGELY REMAIN
OFFSHORE WITH A DRY SUB-CLOUD LAYER HOLDING FIRM OVER LAND.
THICKENING CLOUD COVER COUPLED WITH CONTINUED WEAK WARM AIR
ADVECTION WILL RESULT IN A WARMER NIGHT WITH LOWS RANGING FROM THE
UPPER 40S/NEAR 50 WELL INLAND TO THE LOWER-MID 50S ELSEWHERE. SOME
PATCHY FOG WILL LIKELY DEVELOP ONCE AGAIN...BUT WITH INCREASING
CLOUD COVER SHOULD LIMIT THE FOG COVERAGE COMPARED TO PREVIOUS
MORNINGS.

SUNDAY...SURFACE HIGH PRESSURE WILL HAVE SETTLED OVER THE ATLANTIC
WATERS BY DAYBREAK...AHEAD OF A DEVELOPING COLD FRONT THAT WILL
STRETCH FROM THE APPALACHIANS TO THE EASTERN GULF COAST STATES BY
EARLY EVENING. SHORTWAVE ENERGY RIDING ALONG THE PERIPHERY OF AN
UPPER RIDGE OVER THE BAHAMAS WILL ENHANCE DEEP MOISTURE ALONG THE
FRONTAL ZONE....WITH WAVES OF SURFACE LOW PRESSURE TRACKING UP
FROM THE GULF OF MEXICO. WARM SOUTHERLY FLOW WILL PREVAIL ALONG
THE SOUTHEAST COAST IN BETWEEN THE ATLANTIC HIGH PRESSURE AND
INLAND COLD FRONT...SUPPORTING BOTH UNSEASONABLY WARM TEMPERATURES
PEAKING IN THE LOW TO MID 70S AND STEADILY INCREASING DEWPOINTS.
CONSIDERING THE RESIDUAL DEEP LAYER RIDGING ACROSS THE FORECAST
AREA FOR THE MAJORITY OF THE DAYTIME PERIOD...WILL KEEP RAIN
CHANCES BELOW 15 PERCENT THROUGH THE EVENING HOURS...BEFORE SLOWLY
INTRODUCING ISOLATED TO SCATTERED RAIN ACROSS THE INLAND AREAS
LATE SUNDAY NIGHT. SEA FOG DEVELOPING ACROSS THE NEARSHORE MARINE
ZONES AS WARM/HUMID AIR SETTLES OVER THE COOLER WATERS WILL
POTENTIALLY SPREAD INLAND OVERNIGHT. WILL NEED TO MONITOR FOR THE
POTENTIAL THAT FOG COULD BECOME DENSE...AND WILL CONTINUE TO
MENTION POSSIBLE DENSE FOG CONDITIONS IN THE HAZARDOUS WEATHER
OUTLOOK.

MONDAY...THE UPPER RIDGING WILL GRADUALLY RETREAT FAR TO THE
SOUTH/SOUTHEAST AS WEAKENING SHORTWAVE ENERGY LIFTS ACROSS THE
CAROLINAS AND OFF THE MID ATLANTIC COAST. THE FRONTAL SYSTEM WILL
SHIFT ACROSS THE SOUTHEAST STATES THROUGH THE DAYTIME
HOURS...MOVING OFF THE COAST BY MONDAY NIGHT. WILL INDICATE BEST
RAIN CHANCES MONDAY AFTERNOON WHEN THE FRONTAL ZONE AND ASSOCIATED
CONVERGENCE IS DIRECTLY OVER THE FORECAST AREA...WITH RAIN
COVERAGE MOVING INTO THE MARINE ZONES OVERNIGHT. EXPECT ANOTHER
UNSEASONABLY WARM DAY AND MILD NIGHT...AS MAINLY SOUTHWEST FLOW
PREVAILS DURING FRONTAL PASSAGE. HIGH TEMPERATURES WILL REACH THE
LOW TO MID 70S...WHILE LOW TEMPERATURES ONLY FALL INTO THE LOW TO
MID 50S.

TUESDAY...COOLER AND DRIER WEATHER WILL PREVAIL BEHIND THE DEPARTING
COLD FRONT...AS EXPANSIVE SURFACE HIGH PRESSURE BUILDS WEST WITHIN
NEARLY ZONAL FLOW ALOFT. HIGH TEMPERATURES WILL RANGE FROM THE
UPPER 50S/AROUND 60 DEGREES NORTH TO THE MID 60S SOUTH OF THE
SAVANNAH UNDER SLOWLY DIMINISHING SKY COVER.

&&

.LONG TERM /TUESDAY NIGHT THROUGH FRIDAY/...
EXPECT DRY AND COOLER CONDITIONS ON THE PERIPHERY OF BUILDING
HIGH PRESSURE TUESDAY NIGHT THROUGH WEDNESDAY NIGHT. TEMPERATURES
WILL PEAK IN THE MID 50S NORTH TO UPPER 50S/AROUND 60 SOUTHERN
SECTIONS WEDNESDAY AFTERNOON...WHILE LOW TEMPERATURES FALL INTO
THE UPPER 30S INLAND TO LOW 40S COAST BOTH TUESDAY NIGHT AND
WEDNESDAY NIGHT. THE EXPANSIVE SURFACE HIGH BUILDS ACROSS THE
SOUTHEAST UNITED STATES THROUGH MID WEEK AND SETTLES OVER THE
ATLANTIC WATERS FRIDAY AND SATURDAY. ANOTHER SYSTEM WILL DEVELOP
OVER THE WESTERN GULF OF MEXICO LATE FRIDAY AND LIFT TO THE
NORTHEAST DURING THE WEEKEND. WILL MAINTAIN RAIN FREE CONDITIONS
THROUGH THURSDAY...THEN INTRODUCE CONSERVATIVE RAIN CHANCES LESS
THAN 30 PERCENT FRIDAY AND SATURDAY TO ACCOUNT FOR SOME
UNCERTAINTY REGARDING THE LATE PERIOD SYSTEM. WILL ADVERTISE
SEASONAL TEMPERATURES...WITH A WARMING TREND FRIDAY NIGHT INTO
SATURDAY AHEAD OF THE FRONTAL SYSTEM.

&&

.AVIATION /12Z SATURDAY THROUGH WEDNESDAY/...
VFR. BRIEF VSBY RESTRICTIONS POSSIBLE RIGHT AROUND SUNRISE AS
SHALLOW GROUND FOG BEGINS TO LIFT. LOW PROBABILITIES FOR LOW CIGS
TO DEVELOP OVERNIGHT...BUT THIS SHOULD BE MITIGATED SOMEWHAT BY
A THICKENING SHIELD OF HIGH CLOUDS. WILL MAINTAIN VFR CONDITIONS
FOR NOW.

EXTENDED AVIATION OUTLOOK...IFR OF LOWER CONDITIONS POSSIBLE SUNDAY
NIGHT INTO MONDAY MORNING AS SEA FOG POSSIBLY SPREADS INLAND FROM
OFF THE ATLANTIC.

&&

.MARINE...
TODAY THROUGH TONIGHT...NORTHEAST WINDS 10 KT OR LESS TODAY WILL
BECOME VARIABLE TONIGHT AS HIGH PRESSURE NUDGES SOUTH AND THE
COASTAL TROUGH WELL OFFSHORE DISSIPATES. SEAS WILL REMAIN 3 FT OR
LESS THROUGH THE PERIOD.

SUNDAY THROUGH MONDAY...A LIGHT SOUTHERLY FLOW WILL DEVELOP ON
THE PERIPHERY OF ATLANTIC HIGH PRESSURE THROUGH SUNDAY
NIGHT...BEFORE VEERING A LITTLE FURTHER SOUTHWEST AND INCREASING
IN ADVANCE OF THE NEXT COLD FRONT THAT DROPS INTO THE REGION MONDAY.
WINDS AND SEAS WILL REMAIN BELOW ANY SMALL CRAFT ADVISORY
CONDITIONS THROUGH THE PERIOD. THE MAIN MARINE CONCERN WILL BE
THE FORMATION OF SEA FOG ACROSS THE COOLER SHELF WATERS BY LATE
SUNDAY OR SUNDAY NIGHT...POSSIBLY LINGERING INTO MONDAY. WARMER
AND MORE HUMID AIR OVERRIDING THE COOLER NEAR SHORE WATERS WITHIN
FAVORABLE SOUTHERLY TRAJECTORIES APPEARS HIGHLY FAVORABLE FOR
PERSISTENT SEA FOG FORMATION. HAVE ADDED MENTION TO THE HAZARDOUS
WEATHER OUTLOOK...SINCE DENSE FOG AND MARINE DENSE FOG ADVISORIES
COULD BECOME NECESSARY.

MONDAY NIGHT THROUGH WEDNESDAY...THE COLD FRONT MOVES THROUGH THE
COASTAL WATERS MONDAY NIGHT...FOLLOWED BY CONTINENTAL HIGH
PRESSURE INTO MID WEEK. SOME COLD ADVECTION AND EVENTUALLY A
TIGHTENING OF THE PRESSURE GRADIENT WILL SUPPORT HIGHER WINDS AND
SEAS...AND WILL NEED TO MONITOR FOR POTENTIAL SMALL CRAFT ADVISORY
CONDITIONS TO DEVELOP.

&&

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

&&

$$

ST/WMS






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