FXUS62 KCHS 031232
AFDCHS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
732 AM EST THU DEC 3 2009
.SYNOPSIS...
HIGH PRES WILL BUILD OVER THE REGION THROUGH TONIGHT BEHIND A
DEPARTING COLD FRONT THIS MORNING. A WAVE OF LOW PRES WILL DEVELOP
IN THE GULF OF MEXICO LATE FRI...THEN SHIFT OFF THE SOUTHEAST
COAST FRI NIGHT AND TOWARD THE NORTHEAST STATES BY LATE SAT. HIGH
PRES WILL RETURN FROM THE N SUNDAY THROUGH TUE...AHEAD OF THE NEXT
COLD FRONT MID WEEK.
&&
.NEAR TERM /UNTIL 6 PM THIS EVENING/...
A COLD FRONT WAS PRESSING OFF THE COAST EARLY THIS MORNING. SURFACE
DEW POINTS WERE FALLING FROM W TO E AND SKIES HAVE BECOME PARTLY
CLOUDY. A FEW AREAS OF STRATOCUMULUS WERE STILL AROUND SOUTH
CAROLINA AND SOUTH GEORGIA PRE-DAWN. WIDESPREAD HIGH LEVEL CLOUDS
ENHANCED BY A BROAD ENTRANCE REGION OF A STRONG SOUTHERN STREAM
JET STREAM WERE STREAMING OVER THE SOUTHEAST STATES. WINDS HAVE
SUBSIDED OVERNIGHT...MOSTLY 10 MPH OR LESS AT OBSERVATION SITES
EARLY THIS MORNING.
DESPITE DRYING IN THE LOWER LEVELS...WIDESPREAD HIGH CLOUDS COULD
KEEP SKIES PARTLY TO EVEN MOSTLY CLOUDY AT TIMES. IT CERTAINLY
WILL BE A BRIGHTER DAY THAN ON WED AND WE HAVE SELECTED PARTLY
CLOUDY SKIES AS A COMPROMISE. CAA NOT PARTICULARLY STRONG AND
WILL DOWNSLOPE HIGH TEMPERATURES WILL REACH THE LOWER TO MID 60S
INLAND AND PERHAPS A FEW UPPER 60S CLOSER TO THE CHARLESTON COUNTY
COAST.
LAKE WINDS...WE HELD ONTO A MARGINAL LAKE WIND ADVISORY ON LAKE
MOULTRIE THIS MORNING. THIS WILL LIKELY COME DOWN LATER THIS
MORNING.
&&
.SHORT TERM /6 PM THIS EVENING THROUGH 6 PM FRIDAY/...
SURFACE HIGH PRES WILL BUILD N OF THE REGION TONIGHT. DRY WEATHER
IS ANTICIPATED WITH AN OVERNIGHT INCREASE IN HIGH CLOUDS ON TAP
AS OTHER SYSTEM TAKES SHAPE OVER GULF OF MEXICO. THE AMOUNT AND
THICKNESS OF THE HIGH CLOUDS WILL BE A PLAYER IN LOW TEMPERATURES
BUT WE HAVE CONTINUED GENERAL PERSISTENCE WITH SOME UPPER 30S
WELL INLAND TO LOWER 40S ALONG THE COAST.
WEAK HIGH PRESSURE WILL BRIEFLY BUILD INTO THE SOUTHEAST STATES ON
FRIDAY BEHIND THE COLD FRONT WELL OFFSHORE...WITH HIGH TEMPERATURES
SUPPRESSED IN THE UPPER 50S TO AROUND 60 DEGREES. RAIN FREE WEATHER
WILL BE SHORT LIVED ON FRIDAY...AS WAVES OF LOW PRESSURE DEVELOP
ACROSS THE GULF OF MEXICO AND ALONG THE LINGERING BOUNDARY OFF THE
SOUTHEAST COAST. DEEP MOISTURE WILL LIFT BACK INTO THE AREA
THROUGH THE DAY...AND HAVE THUS INTRODUCED POPS RANGING FROM A
SLIGHT CHANCE FOR INLAND AREAS TO A CHANCE ALONG THE COAST AND
OVER THE WATERS.
&&
.LONG TERM /FRIDAY NIGHT THROUGH WEDNESDAY/...
WARM ADVECTION WILL INCREASE FRIDAY NIGHT...AS AN UPPER LEVEL
SHORTWAVE MOVING ACROSS THE GULF COAST STATES ENHANCES
CYCLOGENESIS IN THE EASTERN GULF OF MEXICO. BOTH GFS AND ECMWF
INDICATE THE MAIN SURFACE WAVE SHIFTING INTO THE ATLANTIC BY
SATURDAY MORNING...FOLLOWING THE SHORTWAVE ENERGY TRACKING
NORTHEAST THROUGH THE DAY. BEST RAIN CHANCES WILL LIKELY BE LATE
FRIDAY NIGHT INTO SATURDAY MORNING...WHEN THE SURFACE LOW PASSES
CLOSEST TO THE COASTLINE AND UPPER LEVEL ENERGY SWINGS FROM THE
MIDLANDS INTO CENTRAL NORTH CAROLINA. THERE REMAINS SOME
DISCREPANCIES IN TIMING AND STRENGTH OF THE COASTAL LOW BETWEEN
MEDIUM RANGE MODELS...HOWEVER QPF FIELDS IN BOTH MODEL SOLUTIONS
ARE HIGHEST FRIDAY NIGHT INTO SATURDAY.
THE FORECAST AREA WILL REMAIN ON THE COOL SIDE OF THE LOW
SYSTEM OVER THE WEEKEND. EXPECT HIGH TEMPERATURES ON SATURDAY TO
REMAIN IN THE LOWER TO MID 50S WITHIN DECENT COLD ADVECTION BEHIND
A COLD FRONT PULLING THROUGH THE REGION SATURDAY AFTERNOON/EVENING.
HAVE TRENDED DOWN RAIN CHANCES FROM SOUTHWEST TO NORTHEAST...AS THE
LOW SYSTEM PULLS AWAY TO THE NORTHEAST AND THE FRONT CROSSES INTO
THE COASTAL WATERS. HAVE THEN INDICATED RAIN FREE CONDITIONS OVER
LAND AREAS THROUGH MONDAY AS HIGH PRESSURE SHIFTS INTO THE AREA
FROM THE WEST.
BOTH GFS AND ECMWF HINT AT THE FORMATION OF A COASTAL TROUGH ON
THE SOUTHERN EXTENT OF THE HIGH PRESSURE SUNDAY THROUGH
MONDAY...AND HAVE THUS MAINTAINED A SLIGHT CHANCE OF SHOWERS OVER
THE MARINE ZONES DURING THIS PERIOD.
LOOK FOR ANOTHER SOUTHERN STREAM SYSTEM TO POTENTIALLY AFFECT THE
AREA TUESDAY INTO WEDNESDAY...WITH TEMPERATURES WARMING UP IN
INCREASING SOUTHERLY FLOW. HAVE RE-INTRODUCED A CHANCE OF RAIN IN
THE FORECAST FOR MID WEEK...AS MODELS ARE IN BASIC AGREEMENT
REGARDING THE GENERAL DEVELOPMENT OF THE SYSTEM AT THIS POINT.
&&
.AVIATION /12Z THURSDAY THROUGH MONDAY/...
VFR CONDITIONS RETURN TO THE AVIATION ARENA TODAY AS DRIER LOW LEVEL
AIR HAS FILTERED INTO THE REGION FROM THE WSW. A FEW 4 KFT CIGS MAY
BRUSH KSAV THROUGH MID MORNING OTHERWISE...MAINLY SCATTERED
STRATOCUMULUS ARE EXPECTED TODAY. W SURFACE WINDS WILL BE BELOW 15
KT.
TONIGHT...VFR WITH LOW POTENTIAL FOR MVFR VSBYS OR EVEN SOME S
GEORGIA STRATUS PATCHES LATE. NO INTRODUCTIONS TO CLOUDS BLO 1 KFT
OR VSBY RESTRICTIONS JUST YET.
EXTENDED AVIATION OUTLOOK...VFR CONDITIONS ARE EXPECTED INTO EARLY
FRI. MVFR OR LOWER CIGS AND VSBYS POSSIBLE DURING THE WEEKEND.
&&
.MARINE...
WITH THE COLD FRONT COMING THROUGH THE WATERS THIS MORNING...THE
AXIS OF STRONG SOUTHERLY LOW LEVEL JET HAS PASSED ON TO THE NE.
WINDS HAVE VEERED SW AND ARE EXPECTED TO CONTINUE TO DIMINISH AND
VEER MORE W DURING TODAY. THE WRF SHOWS A BIT MORE MORNING JETTING
OFF THE GEORGIA COAST THAN THE GFS THIS MORNING AND WE HAVE LEANED
TOWARD THAT SOLUTION. WE HAVE LOWERED ALL OF OUR GALE WARNINGS ON
THIS RELEASE. WE THINK SMALL CRAFT ADVISORIES WILL ALSO COME DOWN
LATER THIS MORNING WITH SEAS DIMINISHED BY THE OFFSHORE FLOW AND
LACK OF MIXING INTO EARLY AFTERNOON.
THE HIGH SURF ADVISORY HAS BEEN LOWERED THIS MORNING AND NO FURTHER
COASTAL ISSUES ARE EXPECTED TODAY.
SURFACE HIGH PRES WILL BRIDGE NW-N OF THE WATERS TONIGHT WITH
SPEEDS MAINLY LESS THAN 15 KT AND DIRECTION BECOMING NORTHERLY
OVERNIGHT. SEAS SHOULD BE DOWN TO 2 TO 4 FT BY TONIGHT.
MODELS ARE INDICATING THAT A WAVE OF LOW PRESSURE WILL DEVELOP
ALONG THE LINGERING COLD FRONT TO THE SOUTHEAST OF THE WATERS
DURING THE WEEKEND. THIS DEVELOPMENT COULD RESULT IN A STRONG
NORTHEAST SURGE SATURDAY AND SUNDAY AS THE SYSTEM PULLS NORTHEAST
AND COLD ADVECTION INITIATES. WINDS AND SEAS WILL BE HIGHLY
DEPENDENT ON THE TRACK AND STRENGTH OF THIS SYSTEM...AS MEDIUM
RANGE MODELS CONTINUE TO DISAGREE ON DETAILS OF ITS EVOLUTION. AT
THIS POINT...HAVE INDICATED SMALL CRAFT ADVISORY WINDS AND SEAS IN
THE OUTER WATERS SATURDAY AFTERNOON INTO SUNDAY MORNING.
WEAK COASTAL TROUGHING COULD DEVELOP ALONG THE SOUTHERN PERIPHERY
OF HIGH PRESSURE BUILDING INTO THE AREA EARLY NEXT WEEK. MAIN
SENSIBLE WEATHER EFFECTS APPEAR TO BE LINGERING RAIN CHANCES OVER
THE COASTAL WATERS.
&&
.CHS WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
SC...LAKE WIND ADVISORY UNTIL NOON EST TODAY FOR SCZ045.
MARINE...SMALL CRAFT ADVISORY UNTIL NOON EST TODAY FOR AMZ350-352-354-
374.
&&
$$
