Area Forecast Discussion
Issued by NWS Charleston, SC

Home | Current Version | Previous Version | Text Only | Print | Product List | Glossary On
Versions: 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50
000
FXUS62 KCHS 300024
AFDCHS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
724 PM EST THU JAN 29 2015

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

&&

.NEAR TERM /UNTIL 6 AM FRIDAY MORNING/...
THURSDAY EVENING...A BAND OF LIGHT SHOWERS/SPRINKLES WAS ADVANCING
INTO INLAND COUNTIES OF THE FORECAST AREA. MOST LOCATIONS WILL NOT
RECEIVE MEASURABLE RAIN AS THESE SHOWERS PUSH INTO DRIER
AIR/TOWARD THE COAST...BUT AN EARLIER ONSET OF SLIGHT CHANCE POPS
IS JUSTIFIED. OTHERWISE...FORECASTS REMAIN ON TRACK AND REQUIRED
MAINLY MINOR ADJUSTMENTS TO HOURLY ELEMENTS TONIGHT.

TONIGHT...THE APPROACHING MID/UPPER LEVEL SHORTWAVE WILL CONTINUE TO
DIVE SOUTHEASTWARD OUT OF THE UPPER MIDWEST AND TOWARD THE SOUTHERN
APPALACHIANS. AS IT DOES...THE ASSOCIATED COLD FRONT WILL PUSH
INTO THE LEE OF THE MOUNTAINS AND THEN CROSS THE FORECAST AREA
LATE TONIGHT. THE MAIN FORECAST ISSUE WITH THE COLD FRONT WILL BE
THE COVERAGE OF ANY SHOWERS ALONG THE FRONT LATER TONIGHT. THE
MODELS HAVE BEEN INCONSISTENT WITH THE AMOUNT OF
PRECIPITATION...FROM NONE AT ALL TO UP TO A TENTH OF AN INCH FROM
RUN TO RUN. THERE IS A NARROW RIBBON OF MOISTURE ALONG THE
CONVERGENCE WITH THE COLD FRONT AND PVA ALOFT WITH THE SHORTWAVE.
THERE IS ENOUGH MODEL CONSENSUS TO GO WITH SLIGHT CHANCE POPS
ACROSS MUCH OF THE FORECAST AREA...AND EVEN A SMALL AREA OF CHANCE
POPS FOR THE TRI- COUNTY REGION. ANY RAINFALL THAT OCCURS WILL BE
LIGHT AND SHORTLIVED...WITH ONLY A FEW HUNDREDTHS OF AN INCH AT
MOST. SKIES WILL BECOME OVERCAST LATE TONIGHT AND INCREASED
SOUTHWEST FLOW AHEAD OF THE FRONT WILL KEEP TEMPERATURES ELEVATED.
LOWS ARE EXPECTED TO FALL INTO THE MID 40S INLAND AND UPPER 40S
CLOSER TO THE COAST.

LAKE WINDS...A COLD FRONT WILL MOVE ACROSS LAKE MOULTRIE LATE
TONIGHT. WINDS WILL INCREASE IN RESPONSE TO THE TIGHTENING PRESSURE
GRADIENT AND FREQUENT GUSTS TO 25 KT ARE EXPECTED. A LAKE WIND
ADVISORY BEGINS AT MIDNIGHT AND RUNS THROUGH THE NIGHT.

&&

.SHORT TERM /6 AM FRIDAY MORNING THROUGH SUNDAY/...
FRIDAY...HIGH PRESSURE WILL BE MOVING IN BEHIND A DEPARTING COLD
FRONT WITH ANY LINGERING SHOWERS NEAR THE COAST ENDING QUICKLY NEAR
DAYBREAK. IT WILL BE A BIT BREEZY...ESPECIALLY IN THE MORNING. SOME
COLD AIR ADVECTION...ESPECIALLY OVER SC...WILL BE OFFSET SOMEWHAT BY
THE WARMING DOWNSLOPE NORTHWEST WINDS. EXPECT HIGHS IN THE MID TO
UPPER 50S WITH SOME AREAS POSSIBLY HITTING 60...ESPECIALLY SOUTH OF
BEAUFORT. HIGH PRESSURE WILL BE MOVING IN FROM THE NORTHWEST FRIDAY
NIGHT MAKING FOR LIGHT WINDS AND GOOD RADIATIONAL COOLING OTHER THAN
SOME HIGH CLOUDS. EXPECT A COLD NIGHT WITH LOWS LIKELY DIPPING INTO
THE UPPER 20S INLAND AND FREEZING MOST OTHER PLACES AWAY FROM THE
IMMEDIATE COAST.

SATURDAY...HIGH PRESSURE WILL SLIDE OVER THE AREA WITH A DRY AND
COOL DAY ON TAP ALTHOUGH THERE COULD BE SOME HIGH CLOUDS AROUND.
HIGHS SHOULD STRUGGLE A BIT GIVEN THE COLD START LIKELY ONLY
REACHING THE MID 50S MOST PLACES...WITH LOWER 50S CLOSER TO THE
SANTEE RIVER AND UPPER 50S POSSIBLE SOUTH OF I-16. A BIT MORE HIGH
CLOUDS EXPECTED SATURDAY NIGHT AS HIGH PRESSURE SLIDES OFFSHORE AND
RETURN FLOW BEGINS TO INCREASE AHEAD OF THE NEXT STORM SYSTEM WELL
TO THE WEST OVER TEXAS. COULD SEE SOME WEAK TROUGHING OFFSHORE BUT
STILL DRY. LOW TEMPS SHOULD BE IN THE MID/UPPER 30S INLAND BUT LOWER
TO MID 40S AT THE COAST.

SUNDAY...ANY COASTAL TROUGH EARLY WILL DISSIPATE DURING THE DAY AS
THE SOUTHERLY LOW-LEVEL JET STRENGTHENS AHEAD OF AN APPROACHING COLD
FRONT. BEST RAIN CHANCES LOOK TO COME LATER IN THE DAY...MAINLY WELL
INLAND AND POSSIBLY SKIRTING THE SC COAST. DESPITE INCREASING
CLOUDINESS TEMPS SHOULD PUSH TO NEAR NORMAL AROUND 60 IN THE
CHARLESTON AREA WITH MID 60S NEAR AND SOUTH OF SAVANNAH.

&&

.LONG TERM /SUNDAY NIGHT THROUGH THURSDAY/...
SUNDAY NIGHT THROUGH MONDAY NIGHT...THERE REMAINS SOME DIFFERENCES
IN MEDIUM RANGE MODEL SOLUTIONS REGARDING THE STRENGTH OF THE LOW
PRESSURE SYSTEM TRACKING JUST TO THE NORTH OF THE FORECAST AREA
SUNDAY NIGHT...AS WELL AS THE AMPLIFICATION OF THE UPPER SHORTWAVE
HELPING TO DRIVE ITS DEVELOPMENT. A BLENDED SOLUTION WILL SHOW THE
LOW SYSTEM DEEPENING ALONG THE VIRGINIA/CAROLINA COASTLINE BY
MONDAY MORNING...WITH THE TRAILING COLD FRONT OFF THE SOUTHEAST
COAST BY EARLY MONDAY AFTERNOON. THE SHORTWAVE WILL FOLLOW THE
SURFACE FRONT QUICKLY OFFSHORE THROUGH THE AFTERNOON/EARLY EVENING
HOURS...WITH SURFACE HIGH PRESSURE BUILDING INTO THE REGION FROM
THE WEST/NORTHWEST MONDAY NIGHT. WILL CONTINUE TO ADVERTISE THE
HIGHEST RAIN CHANCES SUNDAY NIGHT INTO MONDAY MORNING...COINCIDENT
WITH TIMING OF THE COLD FRONTAL PASSAGE. HAVE REMAINED SOMEWHAT
CONSERVATIVE WITH ACTUAL POPS...CAPPING RAIN CHANCES AT 50 PERCENT
OR LESS...DUE TO SOME HINTS IN BOTH ECMWF AND GFS SOLUTIONS OF A
POSSIBLE PRECIPITATION MINIMUM OVER THE AREA. RAIN CHANCES WILL
DECREASE LATE MORNING/EARLY AFTERNOON MONDAY...FALLING BELOW 10
PERCENT BY MONDAY EVENING.

TUESDAY THROUGH THURSDAY...MODEL SOLUTIONS ARE IN TEMPORARY
AGREEMENT THAT THE MAJORITY OF THE DAYTIME HOURS ON TUESDAY WILL
BE DRY...AS SURFACE HIGH PRESSURE BUILDS IN THE WAKE OF THE FRONT
AND QUICKLY PROGRESSES TOWARD THE COASTLINE. MEDIUM RANGE MODELS
THEN SERIOUSLY DIVERGE REGARDING THE DEVELOPMENT OF LOW PRESSURE
IN THE GULF OF MEXICO LATE TUESDAY INTO MID WEEK. THE DIFFERENCES
ARE NOT SUBTLE...WITH THE MORE AGGRESSIVE ECMWF SOLUTIONS DEPICTING
A WAVE OF LOW PRESSURE MOVING UP THE SOUTHEAST COAST AND BRINGING
NOTABLE RAINFALL TO THE AREA FOR EARLY TO MID WEEK. THE WAVE OF
LOW PRESSURE IS CONSIDERABLY DELAYED AND MORE SUBTLE IN THE
GFS...LEAVING LITTLE OPPORTUNITY TO REASONABLY BLEND THE TWO
SOLUTIONS. PREFER TO MAINTAIN SOME PERSISTENCE...AND WILL JUST
INDICATE SLIGHT TO LOW RAIN CHANCES TUESDAY NIGHT THROUGH
WEDNESDAY...WITH DRY WEATHER POSSIBLE BY LATE WEEK. HIGH
TEMPERATURES EACH AFTERNOON WILL BE JUST A FEW DEGREES BELOW
SEASONAL NORMALS. LOW TEMPERATURES COULD ACTUALLY BE A FEW DEGREES
ABOVE NORMAL...ESPECIALLY CONSIDERING POTENTIAL CLOUD COVER
THROUGH THE PERIOD.

&&

.AVIATION /00Z FRIDAY THROUGH TUESDAY/...
VFR MUCH OF THE 00Z TAF PERIOD...EXCEPT FOR BRIEF PERIODS OF MVFR
CEILINGS AROUND THE TIME OF COLD FROPA DURING THE 06Z-12Z TIME
FRAME. ALSO...LOW LEVEL WIND SHEAR WILL DEVELOP FROM 03Z-06Z
UNTIL JUST AFTER 12Z...WHEN WINDS WILL SHIFT TO THE NORTH/NORTHWEST
AND WILL GUST TO 20-25 KNOTS MUCH OF FRIDAY.

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...
TONIGHT...A COLD FRONT WILL APPROACH THE WATERS OVERNIGHT AND WILL
PUSH THROUGH LATE. A WEAK PRESSURE GRADIENT WILL SUPPORT S/SE
WINDS 10 KT OR LESS EARLY...THEN WINDS WILL VEER TOWARD THE SW AND
WILL INCREASE IN RESPONSE TO THE TIGHTENING GRADIENT. WINDS WILL
THEN SHIFT TO THE WEST IMMEDIATELY BEHIND THE FRONT LATE
TONIGHT/EARLY FRIDAY. MODEL SOUNDINGS SHOW A QUICK RAMP UP IN
WIND SPEEDS STARTING AROUND MIDNIGHT AND CONTINUING THROUGH THE
REST OF THE PERIOD. IN FACT...WINDS WILL BE SUPPORTIVE OF
EXPANDING THE CURRENT SMALL CRAFT ADVISORIES TO INCLUDE ALL OF THE
SOUTH CAROLINA WATERS AS WELL AS THE CHARLESTON HARBOR. WILL
CONTINUE TO GO WITH A START TIME OF MIDNIGHT THOUGH THE STRONGEST
WINDS WILL OCCUR LATER IN THE NIGHT. WINDS WILL GENERALLY BE 20-25
KT WITHIN THE ADVISORY AREA...AND 15-20 KT FOR THE NEARSHORE
GEORGIA WATERS. SEAS WILL GENERALLY BE 2-3 FT NEARSHORE...EXCEPT
UP TO 4 FT IN THE CHARLESTON COUNTY WATERS...AND 3-4 FT FOR THE
OUTER GEORGIA WATERS.

FRIDAY THROUGH TUESDAY...A COLD FRONT RAPIDLY PROGRESSING OFFSHORE
EARLY FRIDAY MORNING WILL MAINTAIN ENOUGH OF A PRESSURE GRADIENT TO
KEEP SMALL CRAFT ADVISORY CONDITIONS OVER THE SC AND OFFSHORE GA
WATERS THROUGH AT LEAST THE MORNING. HIGH PRESSURE WILL THEN
STEADILY BUILD INTO THE REGION AND EVENTUALLY SHIFT OFFSHORE INTO
THE WEEKEND. SLIGHT NORTH/NORTHEAST WIND SURGE EXPECTED SATURDAY
NIGHT BEFORE WINDS DIMINISH DURING THE DAY SATURDAY...WITH
CONDITIONS LIKELY REMAINING JUST BELOW ADVISORY LEVELS...ALTHOUGH A
MARGINAL ADVISORY COULD BE NEEDED OVER THE CHARLESTON NEARSHORE
WATERS AND OFFSHORE GA WATERS.

A STRENGTHENING LOW PRESSURE SYSTEM WILL TRACK NORTH OF THE AREA
MONDAY...WITH ITS TRAILING COLD FRONT SWEEPING THROUGH THE REGION
MONDAY MORNING. INCREASING SOUTHERLY FLOW AHEAD OF THE FRONT...AS
WELL AS NORTHWEST FLOW IN ITS WAKE WILL LIKELY CREATE SMALL CRAFT
ADVISORY CONDITIONS OVER PORTIONS OF THE LOCAL WATERS LATE SUNDAY
NIGHT INTO MONDAY NIGHT. HIGH PRESSURE BUILDING IN TUESDAY WILL
THEN LEAD TO IMPROVING CONDITIONS.

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
SC...LAKE WIND ADVISORY FROM MIDNIGHT TONIGHT TO 1 PM EST FRIDAY
     FOR SCZ045.
MARINE...SMALL CRAFT ADVISORY FROM MIDNIGHT TONIGHT TO 1 PM EST FRIDAY
     FOR AMZ330-350-352-374.

&&

$$
SYNOPSIS...
NEAR TERM...BSH/SPR
SHORT TERM...RJB
LONG TERM...WMS
AVIATION...BSH/RJB/SPR
MARINE...BSH/RJB/SPR


USA.gov is the U.S. government's official web portal to all federal, state and local government web resources and services.