Area Forecast Discussion
Issued by NWS Charleston, SC

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000
FXUS62 KCHS 051542
AFDCHS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
1042 AM EST THU MAR 5 2015

.SYNOPSIS...
A COLD FRONT WILL APPROACH FROM THE WEST AND NORTHWEST TODAY AND
PUSH OFFSHORE THIS EVENING. COLDER HIGH PRESSURE WILL BUILD OVER
THE AREA THURSDAY NIGHT AND WILL PREVAIL INTO SUNDAY. NEXT
WEEK...AN UNSETTLED PATTERN WILL DEVELOP BETWEEN A STATIONARY
FRONT SOUTH AND EAST OF THE REGION AND HIGH PRESSURE CENTERED TO
THE NORTH.

&&

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
LATE THIS MORNING...THE FORECAST AREA IS POSITIONED WELL WITHIN
THE WARM SECTOR AND WARM SUN IS SPILL ACROSS MOST OF IT. VISIBLE
SATELLITE IMAGERY SHOWS A WELL DEFINED AREA OF SEA FOG ALONG AND
JUST OFF THE COAST...AND ANY FOG THAT HAD ADVECTED ONSHORE EARLIER
HAS DISSIPATED WITH STRONG INSOLATION AND RETREATED BACK OVER THE
COOLER SHELF WATERS. THE MAIN FORECAST ISSUE FOR TODAY REVOLVES
AROUND THE APPROACHING COLD FRONT AND PRECIPITATION CHANCES
ASSOCIATED WITH IT. THE COLD FRONT IS CURRENTLY INTERACTING WITH
THE SOUTHERN APPALACHIANS AND SLIPPING INTO THE LEE. SURFACE
OBSERVATIONS SHOW THE FRONT EXTENDS FROM CENTRAL NORTH
CAROLINA...ACROSS THE UPSTATE AND DOWN THROUGH CENTRAL GEORGIA.
RECENT RUNS OF THE HRRR AND RAP SEEM TO HAVE A GOOD HANDLE ON THE
FRONT AS WELL AS THE CURRENT PRECIPITATION COVERAGE...AND THEY
HAVE BEEN USED EXTENSIVELY FOR FORECAST UPDATES. MOST OF THE DAY
WILL BE DRY UNTIL THE FRONT BEGINS ENTERING FROM THE WEST AROUND 2
PM. THE DAMPENING UPPER WAVE ALOFT WILL REMAIN TO THE WEST AND
NORTHWEST OF THE AREA...AND THE FRONT WILL INCREASINGLY BECOME
DISPLACED FROM ANY PVA ALOFT. THERE IS A POWERFUL 180 KT JET ALOFT
AND THE REGION WILL BE SOLIDLY IN THE RIGHT ENTRANCE REGION OF
IT...SO THAT WILL HELP PROVIDE BROAD ASCENT. BY THE TIME THE FRONT
REACHES THE FORECAST AREA IT APPEARS THERE WILL BE MAINLY A BROKEN
LINE OF SHOWERS JUST BEHIND THE LEADING EDGE. THERE CONTINUES TO
BE A SLIGHT CHANCE FOR THUNDER...ESPECIALLY GIVEN THE INCREASINGLY
WARM SURFACE TEMPERATURES. IT WILL BE A BREEZY DAY WITH WINDS
GUSTING TO AS HIGH AS 35 MPH AT TIMES. FINALLY...IT WILL ONCE
AGAIN BE ANOTHER AFTERNOON WITH WELL ABOVE NORMAL TEMPERATURES. IN
FACT...WE WILL LIKELY COME CLOSE TO RECORDS AT KCHS AND KSAV.

&&

.SHORT TERM /6 PM THIS EVENING THROUGH SUNDAY/...
TONIGHT...RAIN CHANCES WILL STEADILY END FROM WEST-EAST THIS
EVENING AS THE COLD FRONT PUSHES THROUGH. THE BULK OF THE
MEASURABLE RAINS WILL BE OFFSHORE 9 PM TO MIDNIGHT WITH ONLY
ISOLATED TO PERHAPS SCATTERED SHOWERS LINGERING THROUGH EARLY
FRIDAY. IN THE WAKE OF THE PRIMARY RAIN BAND...LOW CEILINGS AND
PERIODS OF DRIZZLE WILL FILL IN AS COLDER AIR PUSHES SOUTH.
TEMPERATURES COULD BE NEAR FREEZING ACROSS UPPER PORTIONS OF
DORCHESTER AND BERKELEY COUNTIES AFTER 4-5 AM. ALTHOUGH SOUNDINGS
SHOW MID-LEVEL MOISTURE QUICKLY SCOURING OUT BY THIS TIME...DEEP
MOISTURE WITHIN THE BOUNDARY LAYER WILL SUPPORT PERIODS OF
DRIZZLE. THIS OPENS THE POSSIBILITY FOR A LITTLE FREEZING DRIZZLE
BY SUNRISE FRIDAY...ROUGHLY ALONG AND NORTH OF SAINT GEORGE-
RIDGEVILLE-HUGER-SHULERVILLE LINE. WITH ONLY MARGINALLY COLD
CONDITIONS AND TEMPERATURES HOLDING RIGHT AT FREEZING...
SIGNIFICANT IMPACTS APPEAR UNLIKELY ATTM. HOWEVER...A VERY LIGHT
GLACE ON ELEVATED SURFACES SUCH AS TREES...METAL OBJECTS AS WELL
AS SOME BRIDGES AND OVERPASSES CAN NOT BE COMPLETELY RULED OUT.
GROUND CONDITIONS WILL BE TOO WARM TO SUPPORT ICE ACCUMULATIONS
OTHERWISE...WHICH INCLUDES NON-ELEVATED ROADWAYS. GIVEN THE
MARGINAL NATURE OF THIS EVENT...THE FORECAST WILL CALL FOR PERIODS
OF DRIZZLE WITH A CHANCE OF FREEZING DRIZZLE IN THE AFOREMENTIONED
AREAS. THE RISK FOR FREEZING DRIZZLE WILL SURGE SOUTH AFTER
SUNRISE AS SUBFREEZING WET-BULB TEMPERATURES ADVECT SOUTH.

LOWS WILL RANGE FROM AROUND FREEZING FAR NORTH TO THE LOWER-MID
40S SOUTH OF INTERSTATE 16 IN SOUTHEAST GEORGIA. ONE COULD ARGUE
THAT A FREEZE WARNING IS NEEDED FOR PARTS OF DORCHESTER AND
BERKELEY COUNTIES NOW THAT ITS BEYOND 1 MARCH AND THE GROWING
SEASON HAS BEGUN. HOWEVER...GIVEN THE TRANSIENT NATURE OF THE
FREEZING LINE AND CONSIDERING A MUCH MORE SIGNIFICANT AND
WIDESPREAD FREEZE WILL OCCUR FRIDAY NIGHT...A FREEZE WARNING WILL
NOT BE ISSUED.

FRIDAY...MODELS HAVE TRENDED DRIER IN THE LOW LEVELS AS COMPARED
WITH RECENT RUNS. THUS...EVEN AS THE COLDEST AIR FEATURING TEMPS
AROUND FREEZING AND WET BULB TEMPS JUST BELOW FREEZING SPREADS
ACROSS INLAND AREAS BETWEEN THE EDISTO RIVER/INTERSTATE 26 AND THE
SANTEE RIVER...LOW LEVEL MOISTURE NOW APPEARS BARELY SUFFICIENT TO
SUPPORT ANYTHING MORE THAN DRIZZLE. THUS...THE PROBABILITY FOR ANY
FREEZING PRECIPITATION HAS DIMINISHED...ALTHOUGH A SLIGHT
CHANCE/CHANCE OF FREEZING DRIZZLE IS STILL JUSTIFIED ACROSS
NORTHERN/INLAND LOCATIONS THROUGH MIDDAY FRIDAY...POSSIBLY A FAR
SOUTH AS A WALTERBORO-NORTH CHARLESTON-MCCLELLANVILLE LINE. EVEN
IF A BIT OF FREEZING DRIZZLE OCCURS ANY TRACE AMOUNTS OF GLAZE
SHOULD ONLY OCCUR ON ELEVATED SURFACES SUCH AS TREES AND STREET
SIGNS...GREATLY LIMITING ANY IMPACTS.

FARTHER SOUTH/EAST WHERE DEEPER MOISTURE WILL RESIDE AND SLIGHT
CHANCE/CHANCE POPS ARE JUSTIFIED THROUGH MIDDAY/EARLY AFTERNOON...
TEMPERATURES WILL REMAIN ABOVE FREEZING. IN GENERAL...GUIDANCE HAS
TRENDED TOWARD A SLOW BUT STEADY DRYING TREND...SO POPS DECREASE
WITH TIME FRIDAY AFTERNOON AND FALL TO NEAR ZERO FRIDAY NIGHT.

ASIDE FROM ANY PRECIP TYPE CONCERNS...FRIDAY WILL PROVIDE
TEMPERATURES SOME 35-40F COLDER THAN THOSE OF THURSDAY...ONLY
RECOVERING INTO THE UPPER 30S TO MID 40S.

FRIDAY NIGHT...CONFIDENCE IS HIGH THAT SUB-FREEZING TEMPERATURES
WILL OCCUR ACROSS MOST SOUTH CAROLINA LOCATIONS AND ACROSS SE
GEORGIA LOCATIONS WEST OF I-95...AND A HARD FREEZE IS POSSIBLE WELL
INLAND. PER COLLABORATION WITH WFO JAX...WILL DEFER DECISIONS
REGARDING FREEZE WATCHES/WARNINGS TO SUBSEQUENT FORECAST PACKAGES.

DESPITE SUNSHINE...TEMPERATURES WILL REMAIN BELOW NORMAL
SATURDAY...RANGING FROM THE MID/UPPER 50S NORTH OF I-16 TO THE LOWER
60S SOUTH.

SATURDAY NIGHT...TRANQUIL CONDITIONS WILL PREVAIL...AND LOW TEMPS
WILL RANGE FROM THE LOWER/MID 30S WELL INLAND TO THE MID 40S ALONG
THE GA COAST.

SUNDAY...MID/HIGH LEVEL CLOUDS WILL INCREASE/THICKEN AHEAD OF A WAVE
OF LOW PRESSURE APPROACHING FROM THE WEST. HOWEVER...NO RAIN IS
EXPECTED DURING THE DAYLIGHT HOURS. ON THE POSITIVE SIDE...
TEMPERATURES SHOULD RECOVER INTO THE 60S SUNDAY...CLOSER TO NORMAL
FOR EARLY MARCH.

LAKE WINDS...FAVORABLE MIXING PROFILES WILL DEVELOP THIS EVENING
AND PERSIST THROUGH THE NIGHT AS COLD AIR INTENSIFIES. EXPECT
NORTH WINDS OF 20 KT WITH FREQUENT GUSTS TO 25 KT TO PREVAIL
THROUGH THE NIGHT...SO A LAKE WIND ADVISORY WILL BE ISSUED. GUSTY
CONDITIONS WILL PERSIST THROUGH FRIDAY MORNING BEFORE DIMINISHING.
WAVES ON THE OPEN LAKE WATERS WILL BUILD TO 1-2 FEET.

&&

.LONG TERM /SUNDAY NIGHT THROUGH WEDNESDAY/...
BETWEEN A STATIONARY FRONT OFF THE SOUTHEAST COAST AND ACROSS THE FL
PENINSULA AND HIGH PRESSURE CENTERED NORTH OF THE REGION...A
BAROCLINIC ZONE WILL WAVER OVER THE REGION AND WILL CONTRIBUTE TO
UNSETTLED CONDITIONS NEXT WEEK. WHILE A MOSTLY CLOUDY REGIME
PUNCTUATED BY PERIODS OF PRECIPITATION AND FINALLY DEVOID OF ANY
COLD AIR APPEARS LIKELY...CONFIDENCE REGARDING COMPLEX FORECAST
DETAILS REMAINS LOW. FOR INSTANCE...WE MAINTAIN CHANCE POPS MONDAY
AND TUESDAY...BUT SOME GUIDANCE SUGGESTS THAT LIKELY/CATEGORICAL
POPS WILL EVENTUALLY BE NEEDED FOR THIS PERIOD. ALSO...THE POTENTIAL
FOR THUNDERSTORMS COULD INCREASE...BUT THE UNCERTAIN DETAILS
REGARDING INDIVIDUAL WAVES OF LOW PRESSURE AND AN ASSOCIATED
UNCERTAIN POTENTIAL FOR AN INFLUX OF ANY SIGNIFICANT INSTABILITY
DOES NOT JUSTIFY ANY MENTION OF THUNDER.

&&

.AVIATION /16Z THURSDAY THROUGH MONDAY/...
VFR AT THE SITES THROUGH LATE AFTERNOON. CONDITIONS WILL CRASH
RAPIDLY TO SUB-IFR BY 22-00Z AS A COLD FRONT PUSHES THROUGH. LIGHT
TO MODERATE RAINS WILL AFFECT THE TERMINALS WITH THE FRONT WITH
LOW CLOUDS/DRIZZLE TO FILLING IN BEHIND THE MAIN RAIN BAND HAS IT
PUSHES OFFSHORE. LIFR CIGS ARE MOST LIKELY AT KCHS. GUSTY WINDS
WILL AFFECT THE TERMINALS FOR THE NEXT 24 HOURS...BOTH IN THE WARM
SECTOR AND IN THE POST-FRONTAL COLD SECTOR.

EXTENDED AVIATION OUTLOOK...VFR LIKELY FRIDAY PM THROUGH THIS
WEEKEND. FLIGHT RESTRICTIONS POSSIBLE IN RAIN EARLY NEXT WEEK.

&&

.MARINE...
TODAY...DENSE SEA FOG CONTINUES ACROSS THE NEAR SHORE WATERS LATE
THIS MORNING AND WILL PERSIST INTO THE EARLY AFTERNOON. CONDITIONS
HAVE IMPROVED SIGNIFICANTLY IN THE CHARLESTON HARBOR AND THE
ADVISORY THERE HAS BEEN ALLOWED TO EXPIRE. THE MOST
WIDESPREAD/DENSE SEA FOG WILL OCCUR OVER THE SOUTH CAROLINA
NEARSHORE WATERS WHERE SOUTHWEST WINDS WILL PROVIDE LONGER PARCEL
RESIDENCE TIMES OVER THE COLD SHELF WATERS. WILL EXTEND THE MARINE
DENSE FOG ADVISORY THROUGH 2 PM...ALTHOUGH IT IS POSSIBLE THE
GEORGIA NEARSHORE WATERS CAN BE REMOVED PRIOR TO THAT GIVEN THE
LESS THAN IDEAL TRAJECTORY STRUCTURE THAT FAR SOUTH.
OTHERWISE...SOUTH TO SOUTHWEST WINDS OF 15 KT OR LESS WILL PERSIST
WITH SEAS 2-4 FT NEARSHORE WATERS AND 3-5 FT OVER THE CHARLESTON
COUNTY AND GEORGIA OFFSHORE WATERS.

TONIGHT...CONDITIONS WILL DETERIORATE RAPIDLY THIS EVENING AS A
COLD FRONT PUSHES OFF THE COAST AND STRONG COLD AIR ADVECTION
ENSUES. THE COMBINATION OF STRONG POST-FRONTAL COLD AIR ADVECTION
AND STRONG ISALLOBARIC PRESSURES RISES WILL SUPPORT GALES FOR
MUCH OF THE NIGHT OVER THE GEORGIA OFFSHORE WATERS AND THE
CHARLESTON COUNTY WATERS WHERE FREQUENT GUSTS TO 35-40 KT GALES
WILL OCCUR. THE HIGHEST WINDS WILL OCCUR OVER THE GEORGIA OFFSHORE
WATERS...ROUGHLY BEYOND 40 NM...WHERE CONTRAFLOW ALONG THE
WESTERN WALL OF THE GULF STREAM WILL BE AT ITS STRONGEST. THE GALE
WATCH WILL BE UPGRADED TO A WARNING FOR THESE WATERS BEGINNING AT
6 PM AND CONTINUING THROUGH THE NIGHT. FOR THE OTHER NEARSHORE
ZONES...INCLUDING THE CHARLESTON HARBOR...WINDS WILL REMAIN JUST
BELOW GALE FORCE...SO SMALL CRAFT ADVISORIES WILL BE MAINTAINED.
SEAS WILL BUILD TO 4-6 FT NEARSHORE WATERS AND 6-8 FT OFFSHORE
WATERS.

FRIDAY THROUGH MONDAY NIGHT...GALES WILL TRANSITION TO SMALL
CRAFT ADVISORIES FRIDAY...AND ELEVATED N/NE WINDS AND ASSOCIATED
SEAS WILL PERSIST INTO SATURDAY. A MORE TRANQUIL REGIME IS
EXPECTED AS HIGH PRESSURE SHIFTS OVER THE WATERS SATURDAY NIGHT
THROUGH SUNDAY. THEN...FORECAST CONFIDENCE DECREASES NEXT WEEK AS
WINDS/SEAS WILL DEPEND ON A HIGHLY UNCERTAIN STORM TRACK. THE
LATEST FORECAST HOLDS WINDS/SEAS WELL BELOW SCA LEVELS...BUT AN
OFFSHORE TRACK FOLLOWED BY DEEPER AREAS OF LOW PRESSURE WILL
TRANSLATE TO STRONGER WINDS AND HIGHER SEAS.

&&

.CLIMATE...
RECORD HIGHS FOR 5 MARCH...
KCHS... 85/1997
KCXM... 84/1923
KSAV... 86/1955

RECORD LOW MAXIMUMS FOR 6 MARCH...
KCHS... 43/1960
KCXM... 43/1960
KSAV... 42/1901

&&

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
SC...LAKE WIND ADVISORY FROM 4 PM THIS AFTERNOON TO 2 PM EST FRIDAY
     FOR SCZ045.
MARINE...DENSE FOG ADVISORY UNTIL 2 PM EST THIS AFTERNOON FOR AMZ350-
     352-354.
     SMALL CRAFT ADVISORY FROM 6 PM THIS EVENING TO 4 PM EST FRIDAY
     FOR AMZ352-354.
     GALE WARNING FROM 6 PM THIS EVENING TO 11 AM EST FRIDAY FOR
     AMZ350.
     GALE WARNING FROM 6 PM THIS EVENING TO 2 PM EST FRIDAY FOR
     AMZ374.
     SMALL CRAFT ADVISORY FROM 6 PM THIS EVENING TO 11 AM EST
     FRIDAY FOR AMZ330.

&&

$$

NEAR TERM...BSH
SHORT TERM...SPR
LONG TERM...SPR
AVIATION...SPR
MARINE...SPR
CLIMATE...



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