000
FXUS62 KCHS 071130
AFDCHS

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
630 AM EST SAT NOV 7 2009

.SYNOPSIS...
HIGH PRESSURE WILL REMAIN THE DOMINANT WEATHER FEATURE THROUGH THE
WEEKEND. THE COMBINATION OF A STORM SYSTEM LIFTING OUT OF THE GULF
OF MEXICO AND A COLD FRONT APPROACHING FROM THE WEST WILL KEEP
THINGS UNSETTLED DURING THE EARLY TO MIDDLE PART OF NEXT WEEK.
HIGH PRESSURE WILL THEN BUILD BACK INTO THE REGION BY THURSDAY.

.NEAR TERM /UNTIL 6 PM THIS EVENING/...
SURFACE HIGH PRESSURE WILL CONTINUE TO EXTEND OVER THE AREA TODAY
AS ITS CENTER GRADUALLY MOVES OFF THE COAST OF NORTH CAROLINA AND
INTO THE WESTERN ATLANTIC. MEANWHILE...HEIGHTS WILL RISE ACROSS THE
REGION AS AN UPPER LEVEL RIDGE EXPANDS EASTWARD FROM THE DEEP SOUTH.

AN EXTREMELY DRY AIRMASS...LEADING TO CLEAR SKIES...AND CALM WINDS
EARLY THIS MORNING HAVE RESULTED IN IDEAL RADIATIONAL COOLING
CONDITIONS. SCATTERED FROST IS EXPECTED FOR MANY INLAND LOCATIONS
ACROSS SOUTHERN SOUTH CAROLINA AND SOUTHEAST GEORGIA...THUS NO
CHANGES PLANNED TO THE ONGOING FROST ADVISORY WHICH IS SET TO
EXPIRE AT 8 AM THIS MORNING.

ANTICYCLONIC FLOW AROUND THE SURFACE HIGH PRESSURE SYSTEM WILL
RESULT IN A LOW LEVEL ONSHORE FLOW TODAY. THIS COULD ADVECT JUST
ENOUGH MOISTURE INLAND TO ALLOW FOR SOME STRATOCUMULUS DEVELOPMENT
THIS AFTERNOON...BUT OVERALL SKIES WILL BE SUNNY OR MOSTLY SUNNY.

THE AIRMASS WILL BEGIN TO MODIFY TODAY AS LOW-LEVEL THICKNESS VALUES
SLOWLY INCREASE...GENERALLY SUPPORTING HIGHS IN THE LOWER 70S
ACROSS THE AREA.

.SHORT TERM /6 PM THIS EVENING THROUGH 6 AM SUNDAY/...
UPPER LEVEL RIDGING WILL EXPAND OVER THE SOUTHEASTERN U.S. TONIGHT
AS HIGH PRESSURE AT THE SURFACE LINGERS OVER THE WESTERN ATLANTIC.
A SYNOPTIC ONSHORE FLOW IN THE LOW LEVELS OF THE ATMOSPHERE WILL
CONTINUE TO ADVECT SOME MOISTURE INLAND...BUT TO WHAT EXTENT IS
STILL UNCERTAIN. EITHER WAY DO NOT ANTICIPATE MUCH IN THE WAY OF
CLOUD COVER...WITH THE GREATEST COVERAGE ACROSS NORTH COASTAL
GEORGIA. THE ONSHORE FLOW AND MODERATING AIRMASS WILL NOT ALLOW
TEMPERATURES TO FALL AS SIGNIFICANTLY AS THE PAST COUPLE OF
MORNINGS...WITH LOW TEMPERATURES EXPECTED TO RANGE FROM THE LOWER
40S WELL INLAND TO THE UPPER 40S TOWARD THE COAST. AREAS ALONG THE
IMMEDIATE COAST WILL BE SIGNIFICANTLY WARMER.

.LONG TERM /SUNDAY THROUGH FRIDAY/...
FAIRLY GOOD MODEL AGREEMENT INTO MONDAY LEADS TO HIGHER THAN
NORMAL FORECAST CONFIDENCE...THEN CONFIDENCE LOWERS A BIT THROUGH
MID WEEK DUE TO THE UNCERTAINTY WITH REGARD TO TROPICAL CYCLONE
IDA...OR ITS REMNANTS.

HIGH PRESSURE TO THE NORTH WILL CONTINUE THROUGH MONDAY BEFORE THE
THE HIGH BEGINS TO BREAK DOWN DUE TO THE APPROACH OF A SURFACE AREA
OF LOW PRESSURE FROM THE SOUTH AND AN UPPER LEVEL TROUGH FROM THE
WEST. A STRONG AREA OF HIGH PRESSURE BUILDING IN QUICKLY BEHIND THE
DEPARTING TROUGH TUE NIGHT SHOULD HELP KEEP THE LOW /TC IDA OR ITS
REMNANTS/ SOUTH AND EAST OF THE AREA. HOWEVER...AN INCREASE IN
TROPICAL MOISTURE OVER THE SOUTHEAST ALONG WITH THE APPROACHING
FRONT WILL YIELD INCREASING RAIN CHANCES FROM MONDAY NIGHT AND
TUESDAY. DRIER WEATHER IS THEN EXPECTED BEHIND THE COLD FRONT
WEDNESDAY AND THURSDAY. THE TREND IS FOR LOWER POPS WEDNESDAY SO
HAVE FOLLOWED SUITE BUT DID NOT PULL POPS COMPLETELY JUST YET.
ALSO...AS PWATS INCREASE TO AROUND 2 INCHES /WHICH IS ABOUT 2
STANDARD DEVIATIONS ABOVE NORMAL FOR THIS TIME OF YEAR/ AND THE AREA
BECOMES SITUATED IN A FAVORABLE JET ENTRANCE REGION...THERE IS A
CHANCE FOR AT LEAST A FEW INCHES OF RAIN FROM THIS EVENT.

TEMPERATURES WILL GENERALLY BE NEAR NORMAL THROUGH THE PERIOD EXCEPT
FOR ABOVE NORMAL TEMPERATURES SUNDAY...MONDAY AND FRIDAY.

.AVIATION /12Z SATURDAY THROUGH WEDNESDAY/...
VFR CONDITIONS WILL PREVAIL AT KCHS AND KSAV THROUGH 12Z SUNDAY.
THE AIRMASS WILL REMAIN EXTREMELY DRY THROUGH THIS MORNING AT BOTH
TERMINALS...LEADING TO CLEAR SKIES. HOWEVER...A LOW LEVEL ONSHORE FLOW
COULD ADVECT A FEW STRATOCUMULUS ONSHORE DURING THE AFTERNOON. WINDS
WILL REMAIN BELOW 10 KT THROUGH THE FORECAST PERIOD.

EXTENDED AVIATION OUTLOOK...VFR CONDITIONS WILL PREVAIL THROUGH
MONDAY. THE COMBINATION OF A STORM SYSTEM LIFTING NORTHEAST OUT OF
THE GULF OF MEXICO AND A COLD FRONT APPROACHING FROM THE WEST WILL
RESULT IN UNSETTLED WEATHER AND THE POTENTIAL FOR MVFR OR IFR
CONDITIONS MONDAY NIGHT THROUGH WEDNESDAY. LLWS IS ALSO POSSIBLE
WEDNESDAY MORNING.

.MARINE...
HIGH PRESSURE WILL SHIFT OFFSHORE NORTH OF THE AREA TODAY...CAUSING
NORTHEAST WINDS TO SHIFT EAST THIS AFTERNOON. THE SURFACE PRESSURE
GRADIENT WILL NOT BE TIGHT ENOUGH TO SUPPORT WINDS ANY GREATER
THAN 10-15 KT ACROSS THE WATERS THROUGH THIS AFTERNOON. SEAS WILL
GENERALLY RANGE FROM 2-3 FT ACROSS THE NEARSHORE WATERS AND 3-4 FT
ACROSS THE OUTER GEORGIA WATERS.

HIGH PRESSURE WILL LINGER OVER THE WESTERN ATLANTIC TONIGHT...KEEPING
AN ONSHORE FLOW IN PLACE WITH WIND SPEEDS 15 KT OR LESS AND SEAS 4
FT OR LESS.

SUNDAY THROUGH WEDNESDAY...HIGH PRES WILL REMAIN N OF THE AREA EARLY
NEXT WEEK AS AN AREA OF LOW PRES /POSSIBLY TS IDA/ TRACKS N/NE OUT
OF THE GULF OF MEX. MEANWHILE...A COLD FRONT WILL PUSH ACROSS THE
AREA TUE/TUE NIGHT WHICH WILL KEEP THE LOW S AND E OF THE AREA.
HOWEVER...A VERY STRONG PRES GRADIENT WILL SET UP B/W THE LOW AND A
BUILDING HIGH PRES SYSTEM INLAND. SMALL CRAFT ADVISORIES ARE
EXPECTED ACROSS ALL WATERS BY TUE AND GALES ARE EVEN POSSIBLE
WED/WED NIGHT...ESPECIALLY ACROSS THE WATERS BEYOND 20 NM.

.TIDES/COASTAL FLOODING...
TIDAL DEPARTURES WILL REMAIN ELEVATED THIS MORNING DUE TO A
PERSISTENT NORTHEAST FLOW. THE POSSIBILITY OF COASTAL FLOODING
ALONG PARTS OF THE SOUTHERN SOUTH CAROLINA COAST WILL REMAIN IN
THE HAZARDOUS WEATHER OUTLOOK AS ANOTHER COASTAL FLOOD ADVISORY FOR
SHALLOW COASTAL FLOODING MAY BE NEEDED.

.CHS WATCHES/WARNINGS/ADVISORIES...
GA...FROST ADVISORY UNTIL 8 AM EST THIS MORNING FOR GAZ087-088-
     099101-114-115.
SC...FROST ADVISORY UNTIL 8 AM EST THIS MORNING FOR SCZ040-042045-
     047.
MARINE...NONE.

JAQ/RJB