Area Forecast Discussion
Issued by NWS Charleston, SC

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000
FXUS62 KCHS 301148
AFDCHS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
748 AM EDT THU OCT 30 2014

.SYNOPSIS...
A COLD FRONT WILL MOVE OFFSHORE THIS MORNING...WITH HIGH PRESSURE
THEN BUILDING OVER THE AREA THROUGH FRIDAY. A MUCH STRONGER COLD
FRONT WILL SWEEP THROUGH THE REGION FRIDAY NIGHT...FOLLOWED BY HIGH
PRESSURE BUILDING FROM THE WEST OVER THE WEEKEND. THE HIGH WILL
SETTLE ALONG THE SOUTHEAST COAST EARLY NEXT WEEK BEFORE SHIFTING
OFFSHORE INTO THE ATLANTIC DURING THE MIDDLE OF NEXT WEEK AS ANOTHER
COLD FRONT APPROACHES.

&&

.NEAR TERM /THROUGH TONIGHT/...
A COLD FRONT IS SLOWLY MOVING OFF THE SOUTH CAROLINA COAST AND
THROUGH NORTH COASTAL GEORGIA THIS MORNING. THE BRUNT OF THE
SHOWER ACTIVITY HAS ENDED...BUT CANNOT RULE OUT AN ISOLATED
SHOWER ALONG PART OF THE SOUTH CAROLINA COAST THROUGH MID-
MORNING. THE 850-700 MB TROUGH WILL PERSIST OVER THE SOUTHEAST
STATES TODAY WITH EXTENSIVE MOISTURE AND CONSIDERABLE CLOUDINESS
STICKING AROUND ACROSS OUR EASTERN THIRD. ENOUGH UPLIFT WILL BE
PRESENT OVER OUR COASTAL WATERS FOR SOME ISOLATED SHOWERS TO
DEVELOP DURING THE DAY. COOLER...DRIER AIR WILL GRADUALLY FILTER
INTO THE AREA WITH HIGH TEMPS IN THE LOWER 70S.

WEAK HIGH PRESSURE WILL BUILD IN TONIGHT THOUGH WITH THE
PERSISTING UPPER TROUGH WE EXPECT ENOUGH LOW LEVEL MOISTURE TO
SUPPORT SCATTERED CUMULUS OR STRATOCUMULUS OVER THE WATERS AND
PORTIONS OF COASTAL AREAS. FARTHER INLAND...MODEST RADIATIONAL
COOLING WILL ALLOW FOR LOWS IN THE MIDDLE 40S WHILE ELSEWHERE THE
GREATER SKY COVER AND SLIGHT BOUNDARY LAYER MIXING WILL KEEP TEMPS
IN THE UPPER 40S TO LOWER 50S.

&&

.SHORT TERM /FRIDAY THROUGH SUNDAY/...
FRIDAY...A POTENT SHORT WAVE WILL DIVE OUT OF THE GREAT LAKES REGION
AND INTO THE OHIO VALLEY...RESULTING IN THE AMPLIFICATION OF A MID
AND UPPER LEVEL TROUGH OVER THE EASTERN UNITED STATES. AT THE
SURFACE...THE DEEPENING TROUGH WILL ALLOW FOR CYCLOGENESIS TO OCCUR
OFF THE SOUTHEAST COAST WITH THE DEVELOPING SURFACE LOW LIFTING
NORTHEAST ALONG THE NORTH CAROLINA COAST THROUGH THE DAY. WEAK HIGH
PRESSURE OVER THE REGION WILL RESULT IN RAIN-FREE CONDITIONS BUT IT
WILL BE UNSEASONABLY COOL WITH HIGHS AROUND 70 OR IN THE LOWER 70S
DESPITE MOSTLY SUNNY SKIES.

FRIDAY NIGHT...AN UPPER LEVEL LOW WILL CLOSE OFF AS IT RAPIDLY DROPS
SOUTHEAST ACROSS THE TENNESSEE VALLEY AND INTO THE CAROLINAS. WHILE
THE INITIAL SURFACE LOW CONTINUES TO LIFT NORTHEAST OFF THE
MID-ATLANTIC COAST...ANOTHER SURFACE LOW WILL DEVELOP NEAR THE
SOUTHEAST NORTH CAROLINA COAST AND CAUSE A POWERFUL COLD FRONT TO
SWEEP THROUGH THE AREA OVERNIGHT. THERE APPEARS JUST ENOUGH MOISTURE
WRAPPING AROUND THE NEWLY FORMING SURFACE LOW TO ALLOW ISOLATED
SHOWERS TO DEVELOP ACROSS MAINLY THE CHARLESTON TRI-COUNTY AREA
OVERNIGHT IN CLOSER PROXIMITY TO THE UPPER LOW. GIVEN THE MAGNITUDE
OF THE DEVELOPING COLD POOL ALOFT...THERE IS CERTAINLY THE POTENTIAL
FOR SOME GRAUPEL TO OCCUR BUT WILL NOT INCLUDE MENTION IN THE
FORECAST AT THIS TIME.  COLD AIR ADVECTION AND DEEPER MIXING WILL
DEVELOP BEHIND THE FRONT...WITH TEMPERATURES QUICKLY FALLING LATE
INTO THE LOWER AND MID 40S WITH WINDS BECOMING GUSTY.

SATURDAY...A 535 DECAMETER UPPER LEVEL LOW WILL SWING ACROSS
NORTHERN SOUTH CAROLINA IN THE MORNING...BEFORE SHIFTING OFFSHORE
DURING THE AFTERNOON. THIS HIGHLY ANOMALOUS LOW AND VERY STRONG COLD
AIR ADVECTION WILL RESULT IN 850 MB TEMPERATURES OF -5C...WHICH IS 4
STANDARD DEVIATIONS BELOW NORMAL! NEEDLESS TO SAY...IT WILL BE A
VERY COLD DAY FOR EARLY NOVEMBER WITH HIGHS STRUGGLING TO REACH INTO
THE MID AND UPPER 50S. THIS WILL LIKELY RESULT IN A RECORD LOW
MAXIMUM AT KCHS...BUT SEE BELOW FOR OTHER RECORD INFORMATION. WINDY
CONDITIONS WILL ALSO OCCUR...WITH VERY STRONG LOW LEVEL WINDS OF 30
TO 40 KT DEVELOPING ALONG THE SOUTHERN PERIPHERY OF THE UPPER LOW.
DEEP MIXING PROFILES WILL TAP INTO THE STRONGER WINDS
ALOFT...PRODUCING SUSTAINED WINDS OF 20 TO 30 MPH WITH GUSTS UPWARDS
OF 35 MPH AT TIMES. THERE COULD BE SUFFICIENT MOISTURE WRAPPING
AROUND SURFACE LOW PRESSURE TRACKING OFF THE NORTH CAROLINA COAST TO
PRODUCE ISOLATED SHOWERS ACROSS PARTS SOUTHEAST SOUTH CAROLINA. THE
POTENTIAL FOR GRAUPEL TO OCCUR WILL CONTINUE AS WELL WITH THE CORE
OF THE COLD POOL ALOFT SHIFTING OVER THE AREA. PRECIPITATION CHANCES
WILL DIMINISH IN THE AFTERNOON AS THE SURFACE AND UPPER LOWS BEGIN
TO PULL AWAY.

SATURDAY NIGHT...THE SURFACE PRESSURE GRADIENT WILL REMAIN FAIRLY
TIGHT OVER THE REGION BETWEEN LOW PRESSURE BOMBING OFF THE
MID-ATLANTIC COAST AND HIGH PRESSURE OVER THE MISSISSIPPI VALLEY.
THIS COMBINED WITH CONTINUED COLD AIR ADVECTION WILL KEEP WINDS
COUPLED THROUGH THE NIGHT. TEMPERATURES WILL DROP INTO THE MID AND
UPPER 30S FOR LOWS...WITH COOL TEMPERATURES LIKELY OCCURRING ALL THE
WAY TO THE COAST GIVEN THE ADVECTIVE REGIME.

SUNDAY...SURFACE HIGH PRESSURE WILL BEGIN TO BUILD INTO THE REGION
FROM THE WEST RESULTING IN MAINLY SUNNY SKIES. NORTHERLY FLOW WILL
KEEP TEMPERATURES WELL BELOW NORMAL...WITH HIGHS ONLY
MODERATING INTO THE UPPER 50S OR LOWER 60S ACROSS THE AREA.

LAKE WINDS...THE COMBINATION OF WARM LAKE WATER TEMPERATURES AND
VERY STRONG COLD AIR ADVECTION ALOFT IN WAKE OF A POWERFUL COLD
FRONT FRIDAY NIGHT WILL RESULT IN POTENTIALLY DANGEROUS CONDITIONS
ON LAKE MOULTRIE FOR MARINERS. STRONG WINDS AND ROUGH WAVES ARE
EXPECTED THROUGH SATURDAY NIGHT AND A LAKE WIND ADVISORY WILL
CERTAINLY BE NEEDED.

&&

.LONG TERM /SUNDAY NIGHT THROUGH WEDNESDAY/...
MEDIUM RANGE GUIDANCE IS IN GOOD AGREEMENT WITH THE GENERAL SYNOPTIC
PATTERN THROUGH THE LONG TERM PERIOD. IN THE MID AND UPPER LEVELS OF
THE ATMOSPHERE...A STRONG RIDGE WILL SHIFT EASTWARD AND EXPAND OVER
THE REGION EARLY NEXT WEEK...BEFORE SHIFTING INTO THE ATLANTIC AS A
TROUGH APPROACHES FROM THE WEST DURING THE MIDDLE OF THE WEEK.
MEANWHILE AT THE SURFACE...STRONG HIGH PRESSURE WILL SETTLE ALONG
THE SOUTHEAST COAST EARLY NEXT WEEK THEN SHIFT INTO THE ATLANTIC BY
MID-WEEK...WITH A COASTAL TROUGH POSSIBLY DEVELOPING WEDNESDAY
BEFORE A COLD FRONT MOVES THROUGH THURSDAY.

OVERALL...THIS PATTERN WILL FAVOR RAIN-FREE CONDITIONS EARLY IN THE
WEEK...WITH A SLIGHT CHANCE FOR SHOWERS WEDNESDAY WITH THE COASTAL
TROUGH/ONSHORE FLOW AND THURSDAY WITH THE COLD FRONT. PATCHY FROST
COULD OCCUR INLAND FROM THE COAST SUNDAY NIGHT...WITH SOME FREEZING
TEMPERATURES POSSIBLE IN WELL SHELTERED LOCATIONS AS WELL.
THEN...TEMPERATURES WILL MODERATE THROUGH THE REMAINDER OF THE LONG
TERM PERIOD RETURNING TO NEAR OR SLIGHTLY ABOVE NORMAL BY THE MIDDLE
OF NEXT WEEK.

&&

.AVIATION /12Z THURSDAY THROUGH MONDAY/...
A BRIEF PERIOD OF MVFR OR LOWER CEILINGS IS POSSIBLE THROUGH MID-
MORNING AS A COLD FRONT PUSHES OFFSHORE...BUT OVERALL
PROBABILITIES ARE TOO LOW TO MENTION IN THE TAF/S. OTHERWISE...VFR
CONDITIONS WILL PREVAIL AT THE TERMINALS THROUGH 12Z FRIDAY.

EXTENDED AVIATION OUTLOOK...STRONG WINDS ARE LIKELY AT THE
TERMINALS LATE FRIDAY NIGHT AND SATURDAY AS A COLD FRONT PASSES
THROUGH THE REGION. OTHERWISE...VFR CONDITIONS ARE EXPECTED TO
PREVAIL.

&&

.MARINE...
WINDS WILL BECOME NORTH THIS MORNING AS THE COLD FRONT SHIFTS
OFFSHORE AND HIGH PRESSURE STARTS TO BUILD IN. WIND SPEEDS WILL BE
AROUND 10 KT TODAY...BUT INCREASING TO 10-15 KT TONIGHT WITH AN
INCREASING LOW-LEVEL GRADIENT COMBINED WITH COLD ADVECTION OVER
FAIRLY WARM ATLANTIC WATERS.

FRIDAY THROUGH TUESDAY...HIGH PRESSURE WILL BUILD OVER THE AREA ON
FRIDAY...THEN A POWERFUL COLD FRONT WILL SWEEP OFFSHORE LATE FRIDAY
NIGHT. THE COMBINATION OF WARM SEA SURFACE TEMPERATURES...VERY
STRONG COLD AIR ADVECTION ALOFT AND POTENT LOW LEVEL WIND FIELDS
WILL RESULT IN POTENTIALLY DANGEROUS CONDITIONS FOR MARINERS LATE
FRIDAY NIGHT THROUGH SATURDAY NIGHT WITH GALE CONDITIONS LIKELY.
CONDITIONS WILL IMPROVE EARLY NEXT WEEK...AS HIGH PRESSURE BUILDS
OVER THE REGION.

&&

.CLIMATE...
RECORD LOW MAX TEMPERATURES FOR SAT NOV 1...
KCHS 56 /1993/...
KSAV 52 /1925/...
KCXM 52 /1925/...

&&

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

&&

$$

NEAR TERM...JRL
SHORT TERM...JAQ
LONG TERM...JAQ
AVIATION...JAQ
MARINE...JRL/JAQ
CLIMATE...






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