Area Forecast Discussion
Issued by NWS Charleston, SC

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000
FXUS62 KCHS 281212
AFDCHS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
712 AM EST WED JAN 28 2015

.SYNOPSIS...
HIGH PRESSURE WILL MIGRATE ACROSS THE CAROLINAS TODAY AND
CONTINUE OFFSHORE BY THURSDAY. A COLD FRONT WILL CROSS THE REGION
THURSDAY NIGHT...WITH ANOTHER AREA OF HIGH PRESSURE BUILDING IN
ITS WAKE THROUGH SATURDAY. A COASTAL TROUGH WILL DEVELOP BY
SUNDAY...THEN LIFT NORTH AHEAD OF A COLD FRONT PASSING OVER THE
AREA MONDAY. HIGH PRESSURE WILL THEN BUILD OVER THE REGION NEXT
TUESDAY.

&&

.NEAR TERM /THROUGH TONIGHT/...
LATEST FORECAST REMAINS ON TRACK WITH ONLY MINOR ADJUSTMENTS TO
TEMP TRENDS DURING LATE MORNING HOURS.

TODAY...SFC HIGH PRESSURE WILL CONTINUE TO BUILD FROM THE NORTH AND
NORTHWEST AS ITS CENTER SLIDES EASTWARD FROM THE MIDWEST TO THE
NORTHEASTERN UNITED STATES. ALOFT...A LARGE TROUGH OF LOW PRESSURE
WILL SLOWLY SHIFT OFF THE NORTHEAST SEABOARD...WITH SLIGHT MID LVL
RIDGING OCCURRING LATE. THE COMBINATION OF THE MID/UPPER TROUGH
SHIFTING OFFSHORE AND SFC HIGH PRESSURE BUILDING FROM THE NORTH WILL
CREATE DRY AND COOL CONDITIONS OVER THE FORECAST AREA...WITH OVERALL
HIGH TEMPS REMAINING BELOW NORMAL. IN GENERAL...EXPECT MAX TEMPS
ONLY IN THE UPPER 40S OVER THE TRI-COUNTY AREA TO LOW 50S IN
SOUTHEAST GEORGIA.

TONIGHT...SFC HIGH PRESSURE WILL DOMINATE THE AREA AS IT BECOMES
CENTERED ALONG THE EAST COAST. STRONGER WIND FIELDS ASSOCIATED WITH
THE LONGWAVE TROUGH TO OUR NORTHEAST WILL SLIDE OFFSHORE...ALLOWING
ANY CIRRUS THAT MAY HAVE DEVELOPED OVER THE COURSE OF THE AFTERNOON
TO SHIFT OVER THE WESTERN ATLANTIC WITH A H25 JET MAXIMA. STRONG
RADIATIONAL COOLING IS THEREFORE EXPECTED UNDER CLEAR SKIES EARLY
TONIGHT...WITH WINDS DECOUPLING JUST AN HOUR OR TWO AFTER SUNSET. IN
GENERAL...TEMPS SHOULD DIP INTO THE MID/UPPER 20S INLAND TO LOW/MID
30S ALONG THE COAST.

&&

.SHORT TERM /THURSDAY THROUGH SATURDAY/...
THURSDAY...TRANSIENT UPPER RIDGING WILL TRACK ACROSS THE EAST COAST
AND MOVE OFFSHORE EARLY IN THE DAY...BEFORE A STRENGTHENING
SHORTWAVE TROUGH SLIPS FROM THE OHIO VALLEY INTO THE MID ATLANTIC
AND CAROLINAS OVERNIGHT. SURFACE HIGH PRESSURE FOUND DIRECTLY OVER
THE FORECAST AREA DURING THE MORNING HOURS WILL THUS SHIFT OFF THE
COAST THROUGH THE AFTERNOON...AHEAD OF AN APPROACHING COLD FRONT
ASSOCIATED WITH THE UPPER SHORTWAVE ENERGY. SURFACE FLOW WILL
GRADUALLY VEER FROM NORTHEAST TO SOUTHEAST DURING THE DAYTIME
HOURS...SUPPORTING SEASONAL HIGH TEMPERATURES IN THE UPPER 50S NORTH
TO THE LOW 60S SOUTH. THE MAJORITY OF THE ENERGY WITH THE
APPROACHING SYSTEM WILL REMAIN NORTH OF THE AREA...AND SIGNIFICANT
PRECIPITATION COVERAGE IS NOT EXPECTED WITH FRONTAL PASSAGE. WILL
CONTINUE TO INDICATE JUST A SLIGHT CHANCE FOR RAIN BETWEEN MIDNIGHT
AND DAYBREAK FRIDAY MORNING. LOW TEMPERATURES WILL BE NOTABLY MILDER
THAN THE PREVIOUS NIGHT...RANGING FROM THE LOW TO MID 40S WITHIN
WARM SOUTHWEST FLOW AHEAD OF THE FRONT AND UNDER INSULATING THICK
CLOUD COVER.

FRIDAY...THE AXIS OF THE UPPER SHORTWAVE AND THE COLD FRONT WILL BE
RAPIDLY MOVING OFFSHORE BY FRIDAY MORNING. DRIER NORTHWEST FLOW IN
THE WAKE OF THE SYSTEM WILL BRING AN END TO RAIN CHANCES. COLD
ADVECTION BEHIND THE FRONT WILL BE MITIGATED BY THE WARMING EFFECTS
OF DOWNSLOPE FLOW AND ABUNDANT SUNSHINE...THUS EXPECT HIGH
TEMPERATURES TO STILL REACH THE MID TO UPPER 50S NORTH TO AROUND 60
DEGREES SOUTH OF THE SAVANNAH RIVER. LOW TEMPERATURES WILL BETTER
REFLECT A COLDER AIR MASS IN PLACE...ESPECIALLY AS LIGHT NOCTURNAL
WINDS AND MOSTLY CLEAR SKIES SUPPORT RADIATIONAL COOLING.
TEMPERATURES WILL FALL INTO THE LOW 30S NORTHWEST ZONES TO THE UPPER
30S SOUTHEAST GEORGIA.

SATURDAY...SURFACE HIGH PRESSURE WILL HAVE STEADILY BUILT INTO THE
MID ATLANTIC AND SOUTHEAST STATES BY THE START OF THE WEEKEND. COOL
AND DRY NORTHEAST FLOW WILL SUPPORT HIGH TEMPERATURES BELOW SEASONAL
NORMALS...PEAKING IN THE LOW 50S CHARLESTON TRI COUNTY TO UPPER 50S
SOUTHEAST GEORGIA.

&&

.LONG TERM /SATURDAY NIGHT THROUGH TUESDAY/...
SURFACE HIGH PRESSURE WILL STEADILY SHIFT INTO THE ATLANTIC SATURDAY
NIGHT INTO SUNDAY...WITH A COASTAL TROUGH DEVELOPING OFF THE
SOUTHEAST COAST EARLY SUNDAY. HAVE INTRODUCED RAIN CHANCES BACK INTO
THE FORECAST BY SUNDAY TO ACCOUNT FOR THE INTRUSION OF SHOWERS
ASSOCIATED WITH MOISTURE/CONVERGENCE FROM THE COASTAL TROUGH THAT
WILL BE SHIFTING TOWARD THE SHORELINE. A NEGATIVELY TILTING UPPER
TROUGH WILL BE RAPIDLY MOVING FROM THE CENTRAL PLAINS STATES MIDDAY
SUNDAY TOWARD THE APPALACHIAN REGION EARLY MONDAY...SUPPORTING THE
STEADY PROGRESSION OF A DEEPENING LOW PRESSURE SYSTEM AND ASSOCIATED
TRAILING COLD FRONT TOWARD THE EAST COAST. THE COASTAL TROUGH ON
SUNDAY WILL TRANSITION INTO A WARM FRONT LIFTING NORTH AHEAD OF THE
SYSTEM SUNDAY AFTERNOON...WITH RAIN CHANCES INCREASING SUNDAY NIGHT
INTO EARLY MONDAY AS THE COLD FRONT APPROACHES FROM THE WEST. HAVE
INDICATED HIGHEST POPS OF THE PERIOD FOR SUNDAY NIGHT...HOWEVER
NUMERICAL MODELS COULD SPEED UP OR SLOW DOWN FRONTAL PROGRESSION
THIS FAR IN ADVANCE...POSSIBLY SHIFTING THE WINDOW OF BEST RAIN
COVERAGE ACCORDINGLY.

MEDIUM RANGE MODEL SOLUTIONS SUGGEST THE INTENSIFYING SURFACE LOW
WILL LIFT OFF THE NEW ENGLAND COAST MONDAY AFTERNOON AND PULL THE
COLD FRONT OFF THE EAST COAST BY MONDAY EVENING. SURFACE HIGH
PRESSURE BUILDING IN THE WAKE OF THE FRONT WILL INTRODUCE A PERIOD
OF DRY WEATHER LATE MONDAY INTO TUESDAY. MODELS THEN DIVERGE
REGARDING THE DEVELOPMENT OF LOW PRESSURE IN THE GULF OF MEXICO LATE
TUESDAY INTO WEDNESDAY.

HIGH TEMPERATURES SUNDAY AND MONDAY AHEAD OF THE COLD FRONT WILL
RANGE FROM THE UPPER 50S NORTH TO THE LOW/MID 60S SOUTH. COOLER THAN
NORMALS HIGHS ARE EXPECTED TUESDAY AND POSSIBLY WEDNESDAY BEHIND THE
FRONT...WITH TEMPERATURES GENERALLY PEAKING IN THE 50S.

&&

.AVIATION /12Z WEDNESDAY THROUGH SUNDAY/...
VFR CONDITIONS ARE EXPECTED AT BOTH CHS AND SAV TERMINALS THROUGH
12Z THURSDAY.

EXTENDED AVIATION OUTLOOK...THERE IS A SLIGHT CHANCE FOR RAIN TO
AFFECT THE TERMINALS WITH A PASSING COLD FRONT THURSDAY NIGHT INTO
EARLY FRIDAY. OTHERWISE...VFR CONDITIONS ARE EXPECTED AT BOTH KCHS
AND KSAV INTO THE START OF THE WEEKEND.

&&

.MARINE...
TODAY AND TONIGHT...SFC HIGH PRESSURE WILL BUILD OVER THE WATERS
BEHIND A DEPARTING COLD FRONT...RESULTING IN A PERIOD OF ENHANCED
WINDS OVER WATERS THROUGH LATE MORNING/EARLY AFTERNOON. NORTH
WINDS WILL GUST AS HIGH AS 15-20 KTS...WITH A FEW GUSTS AS HIGH AS
25 KTS IN OFFSHORE GEORGIA WATERS...BEFORE SLOWLY IMPROVING LATE
AFTERNOON. WINDS/SEAS WILL THEN CONTINUE TO DECREASE/SUBSIDE
TONIGHT AND REMAIN WELL BELOW SMALL CRAFT ADVISORY LEVELS FOR ALL
COASTAL WATERS AS HIGH PRESSURE BECOMES CENTERED ALONG THE EASTERN
SEABROAD WITH A MUCH WEAKER PRESSURE GRADIENT DIRECTLY OVER THE
AREA. IN GENERAL...WINDS WILL REMAIN AT OR BELOW 10-15 KTS WITH
SEAS NO HIGHER THAN 2-4 FT TONIGHT.

THURSDAY THROUGH MONDAY...A COLD FRONT WILL APPROACH FROM THE
NORTHWEST THURSDAY AND SUPPORT INCREASING SOUTHWEST WINDS UP TO 15
KT WITH SOME GUSTS TO 20 KT...BEFORE PASSING OFFSHORE EARLY FRIDAY.
WINDS WILL STEADILY VEER TO THE NORTH BEHIND THE DEPARTING FRONT ON
FRIDAY...HOWEVER THE PRESSURE GRADIENT DOES NOT TIGHTEN
SIGNIFICANTLY...AND WINDS/SEAS APPEAR TO STAY BELOW SMALL CRAFT
ADVISORY CRITERIA. THE SURFACE HIGH WILL STEADILY TRACK OFFSHORE AND
INTO THE ATLANTIC OVER THE WEEKEND...WITH A COASTAL TROUGH
DEVELOPING AND MOVING ONSHORE SUNDAY AHEAD OF ANOTHER LOW PRESSURE
SYSTEM TRACKING WELL NORTH OF THE AREA MONDAY. A COLD FRONT TRAILING
FROM THIS SYSTEM IS EXPECTED TO SWEEP THROUGH THE SOUTHEASTERN
UNITED STATES BY MONDAY...WITH WINDS/SEAS POSSIBLY REACHING SMALL
CRAFT ADVISORY LEVELS OVER PORTIONS OF THE MARINE ZONES AS A RESULT.

&&

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

&&

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


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