FXUS62 KCHS 290512
AFDCHS
AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE CHARLESTON SC
1212 AM EST SUN NOV 29 2009
.SYNOPSIS...
HIGH PRES WILL EXTEND ACROSS THE REGION THROUGH MON. A COLD FRONT WILL
MOVE INTO THE AREA FROM THE NW MON NIGHT...THEN STALL S OF THE AREA
ON TUE. A GULF LOW PRES SYSTEM WILL DEVELOP TUE AND MOVE THROUGH THE
MIDLANDS ON WED AND OFF THE MID ATLC COAST WED NIGHT...FOLLOWED BY
HIGH PRES FOR LATE IN THE WEEK.
&&
.NEAR TERM /UNTIL 6 AM THIS MORNING/...
A WEAK SHORT WAVE MOVING THROUGH THE LOWER MISSISSIPPI VALLEY
REGION WAS SPREADING A SHIELD OF HIGH CLOUDS THROUGH A NARROW
RIDGE AXIS ALIGNED NW-SE OVER THE STATE OF GEORGIA THIS EVENING.
WHILE MUCH OF THESE CLOUDS WERE THIN...A FEW DENSER AREAS OF
CIRROSTRATUS APPEAR DESTINED TO REACH EASTERN SOUTH CAROLINA
LATER TONIGHT. THE CLOUDS WERE LIMITING A QUICKER TEMPERATURE
PLUNGE THIS EVENING THAN WE WOULD TYPICALLY SEE DURING SUCH AN
EXCELLENT RADIATIONAL SETUP. MODELS INDICATE BY SUNRISE...THE
GREATEST UPPER LEVEL RH RESIDING OVER OUR SOUTH CAROLINA ZONES
WHILE SOME POTENTIAL FOR LESSER HIGH CLOUDS AROUND DAWN DOWN IN S
GEORGIA...IN PROXIMITY OF THE CENTER OF THE SURFACE HIGH PRES.
WE MADE SOME SLIGHT DOWNWARD TWEAKS TO OUR FORECAST LOW TEMPERATURES
OVER INLAND SE GEORGIA GIVEN THESE SUBTLE TREND SHIFTS THIS EVENING
AND EXPANDED OUR PATCHY FROST MENTIONS S FOR MOST INLAND AREAS OF
SOUTHEAST GEORGIA S OF A LINE FROM METTER TO RINCON.
&&
.SHORT TERM /6 AM THIS MORNING THROUGH 6 PM TODAY/...
HIGH PRESSURE WILL SLOWLY SHIFT OFFSHORE AS THE UPPER RIDGE
FLATTENS ALOFT WITH THE FLOW BECOMING MORE ZONAL. EXPECT A MAINLY
SUNNY DAY WITH HIGHS IN THE LOWER 70S...ABOUT 5 DEGREES ABOVE NORMAL.
&&
.LONG TERM /TONIGHT THROUGH SATURDAY/...
HIGH PRESSURE ACROSS THE AREA SUNDAY NIGHT WILL GIVE WAY TO FAST
MOVING COLD FRONT WHICH SHOULD ACROSS THE AREA MONDAY NIGHT.
MARGINAL MOISTURE COMBINED WITH WILL ONLY WEAK UPPER LEVEL FORCING
SHOULD RESULT IN FARLY LOW CHANCES FOR PRECIPITATION IN ADVANCE
AND WITH THE FRONT. ADDED A SLIGHT CHANCE FOR LATE AFTERNOON
SHOWERS IN THE WEST IN ADVANCE OF THE FRONT WITH A MAINLY A SLIGHT
CHANCE FOR SHOWERS MONDAY NIGHT. IN ADVANCE OF THE FRONT...850 MB
TEMPERATURES FROM 11 TO 12 DEGREES CELSIUS AND DECENT SUNSHINE
SHOULD RESULT IN DECENT MIXING WHICH SHOULD ALLOWS AFTERNOON
TEMPERATURES TO CLIMB INTO THE LOWER 70S IN MOST AREAS.
LOWERED CLOUD COVER AND THREAT FOR RAIN TO NEGLIGIBLE LEVELS FOR THE
LATER HALF OF MONDAY NIGHT THROUGH TUESDAY AS THE COLD LOOKS LIKE IT
WILL DRIVE FURTHER SOUTH THAN EARLIER THOUGHT BEFORE STALLING OUT.
A STRONG UPPER LEVEL SYSTEM CURRENTLY DIVING SOUTHWESTWARD THROUGH
SOUTHERN SOUTH CALIFORNIA WILL SLOWLY MOVE MAINLY EASTWARD AND
INDUCE SURFACE LOW DEVELOPMENT IN THE NORTHWESTER GULF OF MEXICO ON
TUESDAY. MODELS TRACK THE MAIN SURFACE LOW PRESSURE AREA ACROSS INTO
THE OHIO VALLEY BY WEDNESDAY NIGHT WHILE A SECONDARY LOW TRACKS
ACROSS THE SOUTHEASTERN STATES WEDNESDAY AND WEDNESDAY EVENING. THE
UPPER LEVEL SYSTEM IS EXPECTED TO LIFT NEGATIVELY TILTED ACROSS THE
SOUTHEASTERN STATES WEDNESDAY AFTERNOON AND WEDNESDAY NIGHT. GFS AND
ECMWF ARE SIMILAR WITH THE HANDLING OF THIS SYSTEM...ALTHOUGH FAVOR
THE SLIGHTLY SLOWER ECMWF SOLUTION. IT APPEARS THAT RAINFALL AMOUNTS
WILL BE GREATEST FOR FAR INLAND COUNTIES WHERE MORE THAN AN INCH CAN
BE EXPECTED.
MAINLY KEPT FORECAST AS IS BEYOND WEDNESDAY NIGHT...AS DRIER AND
COLDER AIR SPREAD INTO THE AREA. IF THE 12Z GFS MAINTAINS CURRENT
STRENGTH OF COLD AIR FOR LATE IN THE WEEK...LATER SHIFTS WILL LIKELY
NEED TO MAKE SOME ADJUSTMENTS DOWNWARD FOR TEMPERATURES.
&&
.AVIATION /05Z SUNDAY THROUGH THURSDAY/...
VFR CONDITIONS WILL PREVAIL AT KCHS/KSAV THROUGH 06Z MONDAY. COULD
SEE MARGINAL LOW-LEVEL WIND SHEAR AT KCHS AFTER 04-05Z MONDAY AS
1500-2000 FT WINDS ARE FORECAST TO INCREASE TO NEAR 30 KNOTS WITH
SURFACE WINDS AOB 5 KNOTS. SITUATION LOOKS TO MARGINAL TO INCLUDE
IN THE TAF ATTM.
EXTENDED AVIATION OUTLOOK...MVFR OR LOWER CIGS/VSBYS POSSIBLE MON
NIGHT THROUGH WED DUE TO RAIN CHANCES WITHIN UNSETTLED WEATHER.
&&
.MARINE...
TONIGHT...LIGHT AND VARIABLE WINDS AND SEAS MAINLY BELOW 2 FT WILL
CONTINUE OVERNIGHT WITH SURFACE HIGH PRES CENTERED OVER THE LOWER
SOUTH CAROLINA COAST.
SUNDAY...SOUTHERLY WINDS WILL INCREASE AS HIGH PRES SHIFTS FARTHER
OFFSHORE AND A RESULTANT SEA BREEZE DEVELOPS ALONG THE LAND/SEA
INTERFACE. HOWEVER...WINDS WILL REMAIN 15 KT OR LESS WITH SEAS AOB
2 FT.
SUNDAY NIGHT THROUGH THURSDAY...FAIRLY TRANQUIL CONDITIONS THROUGH
MONDAY. THEN THINGS CHANGE FAIRLY SIGNIFICANTLY AS COLD FRONT
MOVES THROUGH AND THEN AN AREA OF SURFACE LOW PRESSURE MOVES
THROUGH THE SOUTHEASTERN STATES DURING THE MID WEEK TIME FRAME.
SMALL CRAFT ADVISORY CONDITIONS SEEM QUITE LIKELY TUESDAY ACROSS
THE OFFSHORE GEORGIA WATERS IN THE WAKE OF THE COLD
FRONT...SUBSIDE SOME TUESDAY EVENING...THEN THE WINDS INCREASE
AHEAD OF THE LOW PRESSURE AREA LATER TUESDAY NIGHT AND INTO
WEDNESDAY. QUITE LIKELY THAT AT LEAST SMALL CRAFT ADVISORIES WILL
BE NEEDED LATE TUESDAY NIGHT AND WEDNESDAY FOR MOST IF NOT ALL
WATERS. THEN STRONG COLD ADVECTION BEHIND THE LOW FROM WEDNESDAY
NIGHT INTO THURSDAY WILL RESULT IN A CONTINUATION OF SMALL CRAFT
ADVISORY CONDITIONS AT LEAST IN THE OFFSHORE GEORGIA WATERS. SEAS
LIKELY TO TOP OUT IN THE 6 TO 8 FOOT RANGE WELL OFF THE COAST
WEDNESDAY NIGHT AND INTO THURSDAY.
&&
.CHS WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
SC...NONE.
MARINE...NONE.
&&
$$
