Area Forecast Discussion
Issued by NWS Charleston, SC

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000
FXUS62 KCHS 301801
AFDCHS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
101 PM EST FRI JAN 30 2015

.SYNOPSIS...
HIGH PRESSURE WILL BUILD INTO THE REGION FROM THE NORTHWEST THROUGH
SATURDAY. A WEAK COASTAL TROUGH WILL DEVELOP SUNDAY AND LIFT NORTH
AHEAD OF A COLD FRONT PASSING OVER THE AREA MONDAY. HIGH PRESSURE
WILL THEN RETURN TO THE REGION TUESDAY BEFORE SHIFTING OFFSHORE
AHEAD OF ANOTHER STORM SYSTEM APPROACHING FROM THE GULF OF MEXICO
LATE IN THE WEEK.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
HIGH PRESSURE WILL BUILD IN FROM THE NORTHWEST BEHIND A DEPARTING
COLD FRONT NOW SOUTH AND EAST OF THE AREA NEAR JACKSONVILLE. DRY
AND GUSTY CONDITIONS WILL PREVAIL ACROSS THE REGION. THE MAIN
SENSIBLE WEATHER FEATURE WILL BE GUSTY NORTHWEST WINDS UP TO 30
MPH...MAINLY THIS MORNING. TEMPS WILL BE A LITTLE TRICKY AS THERE
IS SOME COLD ADVECTION BUT ALSO DOWNSLOPE WARMING. WE KEPT HIGHS
IN THE MID TO UPPER 50S WITH A FEW SPOTS POSSIBLY HITTING 60
DEGREES...MAINLY NEAR AND SOUTH OF SAVANNAH.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH MONDAY/...
TONIGHT...A LINGERING PRESSURE GRADIENT BETWEEN INLAND HIGH
PRESSURE AND THE OFFSHORE COLD FRONT WILL LIKELY KEEP THE BOUNDARY
LAYER SOMEWHAT MIXED THROUGH MUCH OF THE EVENING HOURS BEFORE
DECOUPLING AFTER MIDNIGHT AS THE NOCTURNAL INVERSION DEEPENS AND
THE CORE OF THE SURFACE HIGH DRAWS CLOSER. WITH SOLID RADIATIONAL
CONDITIONS EXPECTED BETWEEN MIDNIGHT AND SUNRISE SATURDAY...HAVE
LEANED CLOSER TO THE COOLER SIDE OF THE GUIDANCE ENVELOP TO
CONSTRUCT OVERNIGHT LOWS. LOWS WILL RANGE FROM THE UPPER 20S WELL
INLAND TO THE LOWER-MID 30S ELSEWHERE...EXCEPT UPPER 30S ALONG
PARTS OF THE GEORGIA COAST. NORTHERLY WINDS OVER LAKE MOULTRIE
WILL ALSO KEEP AREAS IMMEDIATELY DOWNWIND OF THE LAKE A BIT
WARMER...INCLUDING THE MONCKS CORNER AREA.

SATURDAY...SURFACE HIGH PRESSURE WILL STEADILY TRACK OVER THE EAST
COAST STATES DURING THE DAYTIME HOURS...EVENTUALLY MOVING INTO THE
NEARBY ATLANTIC WATERS OVERNIGHT. A COOLER AIR MASS AND NORTHEAST
FLOW WILL REMAIN IN PLACE FOR THE FIRST HALF OF THE DAY...SUPPORTING
HIGH TEMPERATURES SLIGHTLY BELOW NORMAL. TEMPERATURES WILL PEAK IN
THE LOW 50S NORTH TO THE UPPER 50S SOUTH...WHILE MAINLY HIGH CLOUDS
BEGIN TO INTRUDE FROM THE WEST DURING THE LATE AFTERNOON TIME FRAME.
THE INCREASING CLOUD COVER...COMBINED WITH MORE EAST/SOUTHEAST
SURFACE FLOW...WILL MODERATE NIGHTTIME TEMPERATURES A FEW DEGREES
COMPARED TO THE PREVIOUS NIGHT. EXPECT LOW TEMPERATURES TO STAY
ABOVE FREEZING...RANGING FROM THE LOW/MID 30S INLAND TO THE UPPER
30S/AROUND 40 SOUTH AND COAST.

SUNDAY...SURFACE HIGH PRESSURE WILL HAVE SETTLED OVER THE ATLANTIC
BY DAYBREAK...WITH THE NEXT LOW PRESSURE SYSTEM TAKING SHAPE ACROSS
THE MISSISSIPPI VALLEY. A WEAK COASTAL TROUGH ON THE PERIPHERY OF
THE ATLANTIC HIGH COULD GENERATE ISOLATED SHOWERS OVER THE MARINE
ZONES IN THE MORNING. THE COASTAL TROUGH WILL THEN DISSIPATE AND/OR
MOVE ONSHORE AS THE DAY PROGRESSES...AHEAD OF THE DEEPENING LOW
PRESSURE SYSTEM AND TRAILING COLD FRONT MOVING TOWARD THE
APPALACHIANS OVERNIGHT. SHOWERS WILL SPREAD ACROSS THE FORECAST AREA
FROM WEST TO EAST MAINLY BEGINNING IN THE LATE AFTERNOON/EARLY
EVENING. COVERAGE IS THEN EXPECTED TO PEAK BETWEEN MIDNIGHT AND
DAYBREAK MONDAY MORNING...WHEN THE COLD FRONT SHIFTS INTO THE
WESTERN FORECAST AREA. DESPITE THICKENING SKY COVER...EXPECT WARMER
TEMPERATURES SUNDAY AS A RESULT OF INCREASING SOUTHERLY FLOW IN THE
WARM SECTOR OF THE APPROACHING SYSTEM. HIGH TEMPERATURES WILL BE IN
THE LOW TO MID 60S...WHILE LOW TEMPERATURES ONLY FALL INTO THE UPPER
40S TO LOW 50S.

MONDAY...THE COLD FRONT WILL BE CROSSING OVER THE FORECAST AREA
DURING THE MORNING HOURS...AND LIKELY MOVING OFFSHORE NO LATER THAN
EARLY AFTERNOON. SCATTERED SHOWERS ARE THUS STILL EXPECTED THROUGH
THE MORNING...BEFORE DISSIPATING FROM WEST TO EAST IN THE WAKE OF
THE DEPARTING SYSTEM. HIGH TEMPERATURES WILL RETURN TO MORE SEASONAL
NORMALS WITHIN BREEZY WEST FLOW...REACHING THE UPPER 50S TO LOWER
60S AS CLOUD COVER STEADILY DECREASES.

&&

.LONG TERM /MONDAY NIGHT THROUGH THURSDAY/...
RAIN CHANCES WILL DROP BELOW 10 PERCENT BY MONDAY EVENING. LOW
TEMPERATURES MONDAY NIGHT WILL REFLECT THE COOLER AIR MASS IN
PLACE...FALLING INTO THE LOW 30S WEST AND NORTH TO THE MID TO UPPER
30S COAST AND SOUTH. TRANSIENT HIGH PRESSURE WILL MOVE QUICKLY
ACROSS THE EASTERN UNITED STATES IN THE WAKE OF THE DEPARTING LOW
SYSTEM ON TUESDAY. NUMERICAL MODEL SOLUTIONS THEN INDICATE SOUTHERN
STREAM SHORTWAVE ENERGY MOVING INTO THE GULF OF MEXICO AND
GENERATING A LOW PRESSURE SYSTEM ON WEDNESDAY. STRENGTH AND TIMING
DIFFERENCE BETWEEN MODELS ARE STILL QUITE SIGNIFICANT. THERE REMAINS
AT LEAST A 6 HOUR VARIANCE BETWEEN THE FASTER AND SLOWER SOLUTIONS
REGARDING WHEN THE DEEPENING LOW WILL HAVE TRACKED UP TO THE
SOUTHEAST COAST. WILL REMAIN SOMEWHAT GENERIC AND CONSERVATIVE
REGARDING RAIN CHANCES UNTIL THERE IS BETTER MODEL AGREEMENT. AT
THIS POINT...WILL REINTRODUCE RAIN CHANCES BY WEDNESDAY AS A COASTAL
TROUGH DEVELOPS ALONG THE PERIPHERY OF THE SURFACE HIGH OVER THE
ATLANTIC. HAVE THEN INDICATED INCREASING COVERAGE/POTENTIAL OF RAIN
WEDNESDAY NIGHT INTO EARLY THURSDAY...WHEN THE FASTER MODEL SOLUTION
TRACKS THE GULF LOW UP THE SOUTHEAST COASTLINE. ALTHOUGH COVERAGE IS
EXPECTED TO DECREASE FROM WEST TO EAST LATER THURSDAY INTO
FRIDAY...WILL MAINTAIN SLIGHT CHANCE POPS TO ACCOUNT FOR A FEW
SHOWERS THAT COULD BE INITIATED AS AN UPPER TROUGH MOVES ACROSS THE
EAST COAST BEHIND THE DEPARTING LOW SYSTEM.

HIGH TEMPERATURES EACH AFTERNOON WILL GENERALLY BE IN THE 50S.
MONDAY NIGHT WILL BE THE COOLEST...WITH LOW TEMPERATURES EACH NIGHT
THEREAFTER GENERALLY IN THE MID 30S INLAND TO LOW 40S NEAR THE COAST.

&&

.AVIATION /18Z FRIDAY THROUGH WEDNESDAY/...
VFR THROUGH THE 18Z/30 TAF PERIOD. GUSTY NW WINDS NEAR 25 KT
EXPECTED THROUGH THIS AFTERNOON DUE TO A TIGHT PRESSURE GRADIENT
BETWEEN A COLD FRONT NOW WELL OFFSHORE AND INCOMING HIGH PRESSURE.
WINDS WILL SHIFT NORTHERLY THIS EVENING AND DIMINISH OVERNIGHT.

EXTENDED AVIATION OUTLOOK...VFR TO PREVAIL UNTIL SUNDAY NIGHT INTO
MONDAY WHEN MVFR OR POSSIBLY LOWER CONDS ARE POSSIBLE DUE TO A
PASSING COLD FRONT. BREEZY CONDS ALSO LIKELY SUN NIGHT/MON.

&&

.MARINE...
TODAY...MARGINAL SMALL CRAFT ADVISORY CONDITIONS ARE EXPECTED
IN THE WAKE OF A COLD FRONT...MAINLY OVER THE SC WATERS AND
OFFSHORE GA WATERS. OFFSHORE WIND TRAJECTORIES WILL LIMIT SEAS TO
2-3 FT NEARSHORE WATERS WITH 3-5 FT OFFSHORE WATERS.

TONIGHT...EXPECT ANOTHER SLIGHT NORTHERLY WIND SURGE WHICH WILL
KEEP WINDS NEAR ADVISORY LEVELS...ESPECIALLY OVER THE CHARLESTON
COUNTY NEARSHORE WATERS AND OFFSHORE GA WATERS. SEAS COULD BUILD
UP TO 6 FT OUT NEAR 60 NM OFF THE GA COAST.

SATURDAY THROUGH TUESDAY...HIGH PRESSURE WILL BUILD INTO THE REGION
AND EVENTUALLY SHIFT OFFSHORE OVER THE WEEKEND. A STRENGTHENING LOW
PRESSURE SYSTEM WILL TRACK NORTH OF THE AREA MONDAY...WITH ITS
TRAILING COLD FRONT SWEEPING THROUGH THE MARINE ZONES MONDAY
MORNING. INCREASING SOUTHERLY FLOW AHEAD OF THE FRONT...AS WELL AS
NORTHWEST FLOW IN ITS WAKE...COULD SUPPORT SMALL CRAFT ADVISORY
CONDITIONS OVER THE LOCAL WATERS LATE SUNDAY NIGHT INTO MONDAY
NIGHT. HIGH PRESSURE BUILDING INTO THE REGION TUESDAY WILL THEN LEAD
TO IMPROVING CONDITIONS.

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
SC...NONE.
MARINE...SMALL CRAFT ADVISORY UNTIL 5 PM EST THIS AFTERNOON FOR AMZ330-
     352.
     SMALL CRAFT ADVISORY UNTIL 7 AM EST SATURDAY FOR AMZ350-374.

&&

$$
SYNOPSIS...
NEAR TERM...
SHORT TERM...
LONG TERM...
AVIATION...
MARINE...


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